Practical Strawbale Specifics: WALL SECTION

I wanted to start sharing some practical nuts-and-bolts information on natural building.  Starting here with some wall sections that describe the construction of a strawbale wall for an actual project.  A wall section is simply an architectural drawing that shows the construction -- bottom to top -- of a wall system.  The notes in this example are somewhat generic, though some are project-specific.  If you click the image you should link to the full size version of this drawing.  WARNING: it's a really large file, so may take some time to load (depending on your internet speed).  Or feel free to download so you can zoom at will.  But please note that this is copyright protected, so do not share or use without express written permission.

This particular project features rubble trench foundations, shown at the base of the wall, and strawbale exterior walls with lime plaster outside and clay plaster inside.  Also shown are roof tie-in, second floor framing, and a lower porch roof where it meets the strawbale wall.  This project (as all of my strawbale buildings) received a standard building permit for construction.

Please feel free to post questions!!

One Person's Waste...Is Another's Treasure

Salvaging building materials brings new life to otherwise discarded items.  Figuring how to reuse materials can inspire creativity and save loads of money in construction costs.  But you need to have a plan, or you risk spinning your wheels and burning out from all the leg-work involved.

all of the windows for this house are high-quality & energy-
efficient....and yes, they were all salvaged at huge cost savings

Below is the process that I share with my clients who want to make the most of salvage building materials in construction.  The key to success and keeping stress to a minimum is to start early and have a plan!  And don't forget to plan for a place to store what you find that ensures your materials stay protected.

Salvage-Hunting Process...

STEP ONE: make a list

Start by making a list of materials you will need for the project.  This way you know immediately when you see something interesting whether or not you can use it.  Try to avoid just purchasing items with a "maybe this will work...somewhere..." attitude.  You will end up spending a lot of time & money needlessly.
You also will want to track your list.  I use a spreadsheet with at least the following columns:

• item (doors, windows, sinks, flooring, etc.)
• location (this helps you keep track of your salvage items)
• minimum size (what's the smallest your item can be)
• maximum size (what's the largest your item can be)
• special requirements & notes (to help you remember any specifics)

The goal is to have a shopping list to take with you as you go salvage hunting, with reminders of any limitations or special needs that each item has.

This built-in nook makes use of a salvaged church pew, cut to fit.
(The client had "two 4-foot nook benches" in their shopping list.)

STEP TWO: prioritize your list

Big items that can save you the most money include, doors & windows (see more info below), cabinets & counters, fixtures, and flooring. Other items can include framing lumber, railings, overstock insulation, patio pavers, etc. You can prioritize your list one of two ways:

1. By construction timing - which item do you need first, second, third, etc. to keep your construction process flowing smoothly.  I think this method is best if your plan is to do your salvage hunting concurrent with the construction process.
2. By which items can provide the greatest cost savings potential, such as windows, doors, and cabinets. This allows you to start looking for the items that give you the biggest dollar savings for your time spent, and by the time you get to the smaller items on the list you will be a salvage pro.

If you aren't sure how much energy you have in you for the salving hunt, then I would do option #2.  That way, if you start getting overwhelmed by the salvaging, at least you have collected big savings items.

This interior door is an old salvage door with single-pane glass...
not suitable for exterior use...but great for creating interior sound
separation while keeping visual connection between the spaces.

STEP THREE: research baseline pricing

In order to ensure that you don't overpay for your salvage items, you will need to do a little bit of research on what your items would cost if you purchased them new.  This can feel like a big task when you first start, but you will start to get the swing of it as you become a salvage hunting expert.

This counter is made of 3" thick maple, from a repurposed bowling
alley floor.  The total cost was 10% of what the counter would
have cost for new maple (or other solid-surface countertop).

 

STEP FOUR: don't give up performance

For items that have a performance implication, make sure you take that into consideration.  Otherwise you are saving upfront costs, only to find you need to spend money again later for higher energy bills or for replacement.  Performance criteria include:

• durability
• energy efficiency
• structural integrity

For example, if salvage wood will be used structurally, it should be structural grade, show no signs of rot, be free of compromising holes, etc.  For windows, you will want energy efficient, double glazed windows in good condition. If the windows are used for passive solar gain in the winter, the windows also need to NOT have low-e glazing on them.  For appliances, you still want them to be energy efficient. You get the idea...

These wooden posts were salvage from 75+ year old building.
 The wood is hard and dense, and in great shape.  We had a
structural engineer inspect the wood before using it to build with.
(It could also be milled into beautiful flooring or trim.)

STEP FIVE: put in the time

Salvaging requires quite a bit of time & patience, so keep that in mind as you jump in.  And this is why I recommend starting early so you don't find yourself overwhelmed by a "holy heck we need this door tomorrow" moment.  I have included salvage resources that I find to be the most helpful in the region that I work (greater Washington DC/Baltimore MD region).  Feel free to post comments below to share your favorite building material salvage resources.

This metal railing was reused from another part of the same house!
The addition was built over a flat-roofed garage...the garage had a
railing all the way around, that was removed to build this art room.

Some specific Tips...

Salvage doors and windows usually provide the biggest savings for your time investment.  For windows, you have a few options. One is can find local companies that specialize in selling new & replacement windows. They often have a room in the back of new windows that were ordered wrong or were never picked up...orphans, if you will...that they are happy to sell at a discount.  It takes a lot of legwork, but this is a great way to get high quality, new windows for a fraction of the cost.
Used furniture can be nicely converted into a funky bathroom vanity.  You can check yard sales, local thrift shops, and even drive by upper-income neighborhoods early on trash day.
Another great resource is to check for a local Habitat for Humanity "Restore".  They sell donated, salvaged building materials & appliances at a great discount.  See www.habitat.org/restores to search for a ReStore resale outlet nearest you.  Proceeds go directly back to Habitat for Humanity.

RESOURCES

These are my most-used resources in the Washington DC/Baltimore MD metro region.

www.secondchanceinc.org (in Baltimore)

www.rebuildwarehouse.org (in VA, but they have a lot of salvage building materials)

www.communityforklift.com (just outside of DC, in Maryland)

www.restorenova.org (Alexandria, VA)

Building Small Has a Big Payback

Let's get one thing straight right away...When I say "small", I don't mean living in a shoe box.   What I mean by "small" is living in a space that is designed...well designed...for your needs...and no more.  A small space doesn't mean cramped.  What makes a space feel comfortable in a home is not how big it is.  Actually, an expansive space can feel intimidating and alienating, instead of intimate.  Great for large gatherings, but otherwise rarely invoke comfort in a home.

A space that feels comfortable is appropriately sized for its intended activity.

For example, the nook above is in a house with kids.  The parents wanted a game & homework spot for their kids.  We could have designed an extra room, a play room with desks.  But this disconnects the kids' area from the family.  So instead, we designed this nook with built-in benches & a table that is right off the living room.  The kids play games and do homework at the table, and can leave everything out and messy without adding disarray to the family living space.  And the size is less than 25 SF instead of 150 SF for a play room.  At construction costs over $125 per square foot, that puts the direct cost savings at over $15,000.

Why build small?
Building to the size you need (and no more) offers many tangible benefits (besides feeling more comfortable and intimate).  The most obvious benefit, is that a smaller building means fewer materials, which means lower upfront costs for construction.  A smaller house also means lower ongoing bills, since there is less space to heat or cool.  And my personal favorite benefit, is that a smaller space means less to clean!


4 design strategies
So how to build smaller without feeling cramped?  Below are 4 design strategies that make small spaces feel comfortable without feeling claustrophobic.

1. connect to outdoors

One way to make a small space feel more expansive is to connect it visually and/or literally to the outdoors, using windows or glass doors. When you can see beyond the room you are in, your brain sort of "borrows" the space beyond and adds it to expand the one you are in. This is true whether connecting two interior spaces together or adding a visual link to outside.

2. excellent well-lit space

A well-lit space feels larger than a dark space...and natural sunlight creates the best quality light. Designing for excellent light quality means each major space should have sunlight entering from windows on at least 2 directions...that includes light from above. Light entering from two different sides of a room fills in shade spots, balances the light, and reduces glare. Light colored surfaces also help to bounce light within the space.

3. delineate space without walls

There are many, many ways to demarcate where one space ends and another begins without using solid walls.  And when you combine uses into a single space...like cooking with eating...the total footprint can be smaller with the same functionality.  That's because the circulation space is shared.  (Circulation space refers to the floor area needed for moving around.)  So, if you aren't using walls to separate the space, you can use other strategies to mark where one ends and the other begins...like a set of columns, or a kitchen island, or a change in floor material, or a change in ceiling height or material...

4. integrate storage

There are so many creative strategies for integrating storage throughout a house...under stairs, built-in benches with storage, shelving within the wall thickness.  You can store more stuff in less space with a well-designed cabinet than you can in a closet, especially a walk-in closet.  Kindof like a boat interior...where no space is goes wasted.

Resources
There are some great books on designing appropriately-sized homes.  Any of Sarah Susanka's "Not So Big House" books are fabulous (my favorite is below).  The others here offer inspirational photos & examples of small home designs.  Click the book covers for more info or to purchase.

     

     

For more photos & tips for designing smaller, smarter spaces, see our facebook album.

Make Natural, Non-Toxic Paint from CLAY!

The particles of clay are like mini suction cups, which makes clay a create, sticky binder!  Sticky binder, means you have a great way to put pigment (paint) on a wall.  And it's completely natural & non-toxic.

This clay paint recipe can be made from finely sifted clay soil or powdered potter's clay.  If you use clay soil, test it first to determine the proportions of clay to sand, and adjust the recipe below accordingly.  You can watch our video on how to test your soil for clay content on youtube:

This clay paint recipe has an additional binder that helps prevent the paint from being dusty once it dries...that is, wheat paste...which is made simply by boiling flour & water.  Wheat paste can also be used as a glue.  (When we were kids, we used it for a variety of projects, from paper mâché to installing wallpaper.)

Alis/Clay Paint

thick, opaque finish for absorbent wall surfaces; ideal over clay plasters or smooth cob

1 gallon water

4 quarts powdered clay

2 quarts fine sand

1 quart wheat paste (see recipe below)

Pigment, whiting, mica, or chopped straw, as desired

Mix all ingredients together thoroughly, with a large whisk or a paint mixer attachment on a drill (or similar).  Final consistency should be between heavy cream (before it is whipped) and yogurt.  Apply thickly with a good bristle brush.  When leather hard (slightly firm), smooth the surface by buffing with a damp tile sponge.  Rinse the sponge frequently.  Optional final surface treatment: buff with a very flexible Japanese trowel or polished stone, or buff with a dry cloth.

Covers approx. 150 SF

Note on color: you can choose a clay that is the color you want your paint to be...ie, a rusty orange clay will make rusty orange paint.  Or you can use a white base clay and add any natural pigment to achieve any variety of colors, from earthy shades to vibrant colors.  I use pigments from  www.earthpigments.com or www.bioshieldpaint.com.

Wheat Paste
binder added to clay paint

Bring 1 quart water to boil in a non-aluminum pot.  Meanwhile, mix 1 cup flour with 1 cup cold water until smooth and lump free.  (If you can’t get it lump free, run through a strainer.)  When water in pot is boiling, slowly add in flour/water mixture, stirring constantly.  Bring back to almost a boil, stirring constantly, until mixture thickens.  Remove from heat and allow to cool completely.  The top will get a skin on it as it cools.  You can prevent that by stirring as the mixture cools, or by putting a piece of plastic wrap against the surface as it cools.  Or simply peel the skin off before using the wheat paste.  Make wheat paste within a day or two of when you will use it.  It will go rancid after a few days (faster in warm weather), and then is not usable.

Makes approx. 5 cups of wheat paste

Resources

For more general information about natural paints, and links to other natural paint recipes, see our previous blog post: Paint it Green!...with natural paints

I included this book in my last post, but it really is by far my favorite book on natural paint.  The format resembles a cookbook...recipes on one side and a photo of what the paint looks like on the other.  This book contains tons of information and inspiration.

click cover for more info or to purchase

Don't be left with egg on your face...make paint instead!

Have you ever let egg dry on your plate and then tried to wash it off? Pretty tough, huh? That's because eggs are great glue...which means they are great for making paint! You can make two completely different paints with eggs...one paint using the yolk and one with the whites.

these kids learned how to make egg yolk paint in
5 minutes...and then spent hours of fun painting!

Egg Yolk Paint...also called Egg Tempera
Egg yolk paint is super creamy, opaque, and durable. It's great for painting furniture or artwork. You could use it to paint a wall too, but it would take quite a few eggs.

The recipe is simple:
Separate an egg (keep the whites...see below) and let the yolk sit for a few minutes until the skin wrinkles slightly when touched. Pinch or pop the skin of the yolk and drain the yellow liquid into a dish.  (Discard the sac.)  Add up to 1/2 teaspoon of pigment per egg and stir thoroughly. And voila!  You can add a little water as desired if you want to thin the paint. Use this paint right away, because it dries quickly...though continues to harden over several days.  You can layer the paint on furniture or walls, but I recommend waiting 24 hours between coats.

Egg White Paint
Don't waste the other 1/2 of the egg...make an egg white paint with it!  Egg white paint is just as easy to make, but is more delicate than the egg yolk paint.  Use it for surfaces that won't get touched much, like lampshades.  This paint is translucent, like water color, and can be layer to achieve more saturated color.

How to make:
Whisk your egg white(s) to get a slight froth, and then let stand for a few minutes until a clear liquid separates on the bottom.  Remove the froth and discard. Mix in up to 1/2 teaspoon pigment per egg.  This paint dries quickly, so use it right away...

Resources

For more general information about natural paints, and links to other natural paint recipes, see our previous blog post: Paint it Green!...with natural paints

I included this book in my other posts on home made paints, but it really is my favorite book on natural paint. The format resembles a cookbook...recipes on one side and a photo of what the paint looks like on the other. This book contains tons of information and inspiration.

click cover for more info or to purchase

Don't cry over spilled milk...make paint instead!

Milk paint, also called casein paint, is actually made from the curds of the milk, so first you sour it to separate the curds from the whey. (See instructions below.) Milk-based paints work well on a variety of absorbent surfaces, such as drywall, clay plaster, clean wood, or paper. The resulting paint has a slight sheen. It is wipable with a damp cloth but not scrubbable, so don't use it on surfaces that get scrubbed clean. That said, if you use milk paint on wood, you can then seal the wood with tung oil or linseed oil for an incredibly beautiful and durable finish. This is a great paint to make with kids!  My niece likes to paint with milk paints when she visits.

paint samples of various milk paint colors (left side is semi-opaque, right side is translucent)

To make the curds...
To separate the curds from the whey, you basically are souring milk. You can do this one of two ways:  1) let your milk stand in a warm place for several days, undisturbed, and with the lid slightly off OR 2) you can speed the process up by adding 1/2 cup of white vinegar or lemon juice per gallon of milk. The key is to leave the milk completely undisturbed in order for the curds to develop into large particles. If you shake or stir the milk while it is souring, the curds become small and difficult or impossible to strain out. There is a fabulous instructional video online at: http://www.earthpigments.com/video/quark/making-quark.cfm

I have had the best results with 1% or 2% milk, but theoretically any milk will work. Once your milk has soured and separated, you will see white chunks floating over a clear yellowish liquid. This means your milk is done! Strain the curds through a fine strainer or in cheese cloth to discard the liquidy whey. If you are painting walls, I recommend rinsing the curds in cold water a few times to remove any residual whey.

To make milk glaze...
...a translucent pigmented glaze that will cover approximately 40 SF
1 cup strained milk curds (see above)
1½ Tablespoon borax (such as 20 Mule Team, available in the laundry aisle of most supermarkets; optional but I always add it if I'm painting a wall)
¼ cup hot water
approximately 2 Tablespoons pigment (or as desired)
Dissolve the borax completely in the hot water.  Then slowly whisk into the strained milk curds. Stir thoroughly until lump-free. Add pigment to the desired color. This will make a translucent glaze-type paint. If you want to make an opaque paint, you can add 1/2 cup whiting (purchased from an artist supplier and soaked in water overnight) to the recipe above.  Tip for adding pigment:  you can soak your pigment in water overnight and then strain it through cheesecloth if you want to be sure all of your pigment gets fully dissolved in the paint.


To make milk paint...
...an opaque pigmented paint that will cover approximately 20 SF

1 cup strained milk curds

1½ T borax

¼ cup hot water

2-3T (35g) pigment (or as desired)

½ cup (100g) whiting* (soaked in cold water for 24 hours)

Dissolve borax in hot water & allow to cool.  Add borax mixture to strained milk curds & stir thoroughly.  Add whiting & pigment to desired color.  Can be thinned with additional water.  Apply in thin coats, allowing each coat to dry between, or the paint will tend to crack or flake off.

*whiting is high grade calcium carbonate made from finely powdered chalk that can be purchased from any artist supply shop; it is what makes the milk paint opaque.

To paint with milk glaze or paint...
Use any standard application technique: brush, roller, or sponge.  The translucent glaze can be layered with complimentary colors. Apply the paint in thin coats, allowing each coat to dry completely (about 1 to 2 hours).

Resources

For more general information about natural paints, and links to other natural paint recipes, see our previous blog post: Paint it Green!...with natural paints

I included this book in my last post, but it really is by far my favorite book on natural paint.  The format resembles a cookbook...recipes on one side and a photo of what the paint looks like on the other.  This book contains tons of information and inspiration.

click cover for more info or to purchase

Paint it Green! ...with natural paints

Make your own natural paints with ingredients from your kitchen 

What is Natural Paint? 
Before there were paint companies, people made their own paint using natural, non-toxic, often edible ingredients. Natural paints are durable, beautiful, and incredibly easy to make. You can purchase manufactured natural paints, but they can be more expensive. You can also make your own natural paints with ingredients from nature and that you probably have in your kitchen. And then you control the ingredients and the color!

Benefits

• non-toxic: Natural paints do not offgas any chemical toxins into your air, so they are safer to use and safer for your longterm indoor air quality; offgassing ingredients in paint have been linked to dizziness, headaches, and asthsma
• no petrochemicals: the ingredients in natural paints are derived from nature, not non-renewable resources...ingredients like milk, eggs, clay, tree resin, beeswax, bug excretions, etc. 
• no hazardous by-products: the manufacturing process for conventional paints results in a variety of environmentally polluting byproducts; natural paints are derived from nature...trees, milk, soil, etc. 
• less energy to make: the energy needed to make natural paints is YOU...mostly pouring & stirring 
• breathable finishes: this means that the paints don't make a plastic-like finish that traps vapor on either side, which can cause problems with moisture build-up (which can mean mold or rotting) 

natural paints are so easy to make kids can learn it in 5 minutes!

Challenges
When you buy paint, you read the label to see where best to use the paint and you can color match the paint to anything. These are great conveniences and take the guessing out of paint. When you make your own natural paints, you need to understand which paint recipe is appropriate for your particular application. As for color, you have complete control! You can mix absolutely any color, but you may need to experiment a bit to get just the right shade. This means you need to understand your ingredients!

natural paints can be pigmented to absolutely any color

What's in Paint? 
Below are the basic component of any paint.

1. PIGMENT: the point of most paint is to put color on a surface, even if that color is white. Natural pigments are mostly mineral based, like iron oxides, or plant based, like onion skins. You have to make sure the type of pigment you are using will work with the binder you choose or you may end up with a different color than you intended. This is especially true if you have any lime putty in your paint. I order most of my pigments from www.earthpigments.com or www.bioshieldpaint.com.
2. BINDER: the ingredient that transforms pigment into paint is the binder, because it "glues" the pigment onto the wall. If you just used pigment and water, for example, your paint would flake or dust off in no time because the water alone won't glue the pigment to your wall. So you need a binder to attach it. There are a multitude of natural binders in your kitchen, including milk and eggs! Other binders include natural oils, such as tung or linseed oil, clay, gum arabic (from tree resin), beeswax, lime putty, cellulose (from flour), and beer (which some may argue is a waste of beer!)  For a complete collection of recipes, I recommend The Natural Paint Book.  And stay tuned, as I'll be posting paint recipes in weeks to follow.
3. SOLVENT: this ingredient gets a bad name because many solvents used in conventional paints off-gas and are super toxic, but really all the solvent does is thin the consistency of your paint to something you can apply...the solvent can be water!

painting with clay paint...made & on the wall in less than an hour!

Resources
This is by far my favorite book on natural paint.  The format resembles a cookbook...recipes on one side and a photo of what the paint looks like on the other.  This book contains tons of information and inspiration.

click the cover above for more info or to purchase

Stay tuned for paint recipes over the next several weeks.  I'm going to be posting recipes & how to's for milk paint, egg paint, and clay paint.  (And will update here with links as those posts go live.)

Read our recipe & instruction for making home-made MILK PAINT:
http://buildnaturally.blogspot.com/2013/02/dont-cry-over-spilled-milkmake-paint.html
Read our recipe & instruction for making home-made EGG PAINT:
http://buildnaturally.blogspot.com/2013/02/dont-be-left-with-egg-on-your-facemake.html
Read our recipe & instruction for making home-made CLAY PAINT:
http://buildnaturally.blogspot.com/2013/03/make-natural-non-toxic-paint-from-clay.html

Finish Clay Plaster Recipe & Wall Preparation

Plasters made with clay are beautiful, durable, and made from inexpensive and non-toxic ingredients.  Clay creates a breathable finish material with a natural capacity to regulate moisture and temperature in the surrounding air.  Clay naturally absorbs excess moisture in the air, helping air to feel more comfortable in summer, while its high thermal mass creates a battery heat (or cooling) storage that helps to maintain constant air temperature.  Materials can often be found on or local to the building site, making the ingredients dirt cheap...literally.  Or you can use dry bagged clay from a pottery supplier.  Clay naturally occurs in a variety of colors and clay plasters can be pigmented with mineral based pigments in every range of color.  Techniques for mixing and applying are simple and the plaster is extremely forgiving, even for beginners of any age.

Below are instructions for wall preparation to apply clay plaster on drywall or on clay substrates, followed by my favorite finish clay plaster recipe.  At the very end are my 3 favorite plaster books.  Have fun playing in the mud!!

Drywall Preparation
sanded primer for drywall application of clay paints (from Keely Meagan’s article in The Last Straw: www.thelaststraw.org/bonus-articles/earthplaster.html)

• 10 parts wheat paste
• 1 part fine sand (such as mason’s sand)
• 1 part clay

Mix together & paint on wall. Allow to dry completely. Do not re-wet wall surface prior to plaster application.
Covers approx. 40 SF


Wheat Paste
Bring 1 quart water to boil in a non-aluminum pot. Meanwhile, mix 1 cup flour with 1 cup cold water until smooth and lump free. (If you can’t get it lump free, run through a strainer.) When water in pot is boiling, slowly add in flour/water mixture, stirring constantly. Bring back to almost a boil, stirring constantly, until mixture thickens. Remove from heat and allow to cool completely. Use wheat paste within a day or two; it goes rancid after a few days (faster in warm weather), and becomes smelly and usable.
Makes approx. 5 cups of wheat paste.


Clay-Over-Clay Preparation
Dampen clay substrates prior to application of clay paints or plasters. I recommend dampening clay substrates the evening prior to application, again in the morning before you begin to mix your material, and then again about 20 minutes prior to application. Thick cob walls generally require more dampening than clay plaster surfaces.  Be sure to allow your water to completely absorb or you will create a water slick that prevents plaster from adhering to your substrate.  Continue to dampen the wall as you work.


Kaolin Clay Plaster
beautiful white or off-white, creamy plaster that can be pigmented as desired

• 1 gallon water
• 1 part kaolin clay putty*
• 2-½ parts fine sand**
• 1 cup wheat paste per 5-gallon bucket of material (clay and sand)
• Pigment, mica, or chopped straw, as desired

*to make clay putty, soak dry, bagged kaolin clay powder in clean water for a minimum of 24 hours until it is the consistency of sour cream; store in a cool, dry place; kaolin clays are white to off-white, but you can substitute any bagged clay in this recipe in your color of choice

**typical is mason’s sand though finer grit sand may be used; the finer the sand, the smoother the wall surface without buffing with a finish trowel

1. Mix all ingredients together thoroughly. You can use a cement mixer or you can mix materials on a tarp (flipping often & mixing with your feet). Final consistency should resemble creamy mousse. More water may be added to achieve desired consistency.
2. If adding pigment, save some pigmented plaster with no wheat paste for later patches or repairs. Add wheat paste after pigment.
3. Apply plaster to desired texture, typically using trowels, onto substrate that has been prepared as above.
4. When leather hard (slightly firm), smooth the surface by buffing with a damp tile sponge, rinsing the sponge frequently. Or, for a super smooth finish, run a final sweep across the dampened surface with a very flexible trowel. Mist clay surface slightly as desired as you buff with the flexible trowel.

Covers approx. 100 SF


Resources

If you are plastering over strawbales, read our previous posts:
"Clay Plastering Strawbales - FIRST COAT"

"Clay Plastering Strawbales - SECOND COAT"

These are the most useful books I've found for information on making & applying clay plasters.

           

click the book covers above for more info or to purchase

      

Using Natural Finishes: Lime- & Earth-Based Plasters, Renders & Paints, A Step-by-Step Guide by Adam Weismann and Katy Bryce, Green Books Ltd, 2008

Clay Culture: Plasters, Paints and Preservation by Carole Crews, Gourmet Adobe Press, 2010

The Natural Plaster Book: Earth, Lime and Gypsum Plasters for Natural Homes by Cedar Rose Guelberth and Dan Chiras, New Society Publishers, 2003.

Cob Oven Video - Parts Three & Four

Here are our final two videos explaining how to build a cob oven.
For more information on cob ovens, I recommend Kiko Denzer's book "Build Your Own Earth Oven"...it's a complete "how to" including how-to sketches, list of tools, inspiring photos, and much more.

Part Three shows how to carve the door, remove the sand, fire up the oven, and bake a pizza! This oven is 36" interior diameter, so the height of the interior is 75% of that, or 27" tall. The thermal mass layer is 4" thick, plus a 6" thick insulating layer over that, so the whole oven is 10" bigger than the fire cavity all the way around.

Part Four shows how to apply a lime plaster to your cob oven. Lime plaster is made with 3 parts mason's sand and one part lime putty. I use Mississippi vertical hydrate lime, purchased as a powder, and I let it soak in water for a minimum of 6 weeks, until it is the consistency of sour cream. The longer it sits in water, the creamier and nicer to work with it becomes. LIME IS CAUSTIC! So be sure to wear protective clothing and gloves. Never touch it directly! My lime plaster bible is the book "Building with Lime" by Stafford Holmes and Michael Wingate.

Cob Oven Video - Parts One & Two

Here are our first two videos explaining how to build a cob oven.
For more information on cob ovens, I recommend Kiko Denzer's book "Build Your Own Earth Oven"...it's a complete "how to" including how-to sketches, list of tools, inspiring photos, and much more.

Part One shows how to prepare the base and dome mold for building a cob oven. This oven is 36" interior diameter, so the height of the interior is 75% of that, or 27" tall. The thermal mass layer is 4" thick, plus a 6" thick insulating layer over that, so the whole oven is 10" bigger than the fire cavity all the way around. The base is made with stones gathered from the site and held together with a clay + sand (cob) mortar. Also note, the primary reason to use firebrick is that they do not crack under the heat of a fire.

Part Two shows how to mix & install the cob thermal mass layer (no straw) and the insulating layer (lots of straw).  Note that our soil was about 50% clay and 50% sand content.  We want about 25% total clay, so we added an additional 2 parts sand for each 2 parts soil.  Since the soil is already 50-50 sand-to-clay, the total is 1 part clay to 3 parts sand, or 25%.   The thermal mass layer has no straw.  This is the layer that gets hot and holds the heat from your fire.  The second layer has tons of straw...basically as much as you can mix in.  Straw is a good insulator, so the second layer helps hold in your heat.

Low-Cost, High Performing Living Roofs

A living roof, or green roof, describes a system that allows plants to thrive on the surface of rooftop without access to groundwater.  The idea is to create a self-sufficient ecosystem that doesn't need you to water once the plants are fully established.  This type of roof does provide energy-efficiency benefits in the summer, because the plants provide a net cooling effect.  Even one inch of planted soil lowers overall average roof temperatures and reduces day-to-night temperature swings on roof surface.  A green roof does NOT provide insulation to speak of, so you still need to insulate your roof, just like you normally would.  Additionally, plants absorb and filter rainwater, reducing the negative impacts of excess storm runoff in watersheds, which is especially beneficial in areas with high percentage of impervious surfaces, such as cities and suburbs.  (Yes, I did write suburbs!  A mowed lawn only allows an average of 40% of the rain that falls on it to absorb into the groundwater table!)

The most important detail with a living roof is to select plants that will thrive in your climate and with the amount of sunlight striking your roof.  (See below for a living roof plant resource.)  First and foremost, your plants need to be able to survive without access to groundwater and rely just on your local rainfall.  If you get tons of annual rainfall, you will want to be sure you select plants that can handle "wet feet", and be sure your roof drains well.  If your roof is in full sun, you will need to select plants that will not wither under the heat of relentless summer sunshine.  Etc.

full shade allows greater variety of plants

Most planted roofs are installed on reasonably flat surfaces.  But this is by no means a requirements.  Steeper roofs (above about a 30-degree slope) do require additional erosion control, especially while the plants establish their root systems.  Most commonly, I use a wooden trellis type grid that rests directly on the drainage layer (not fastened to the roof).  Then plant in between the grid of the trellis.  As the plants establish their root system, the wood biodegrades, providing additional nutrients for the plants.  By the time the wood has composted, your plant roots become your erosion control.

plants thrive on shallow or steep slopes, even curves!

Here are the layers I have used with great success on numerous small scale roofs:

1. sheathing (such as plywood) - typical roof sheathing is 1/2", but my engineer likes to bump it up to 5/8" to prevent any sagging from the weight of the soil.  The sheathing is part of your structure, so I make sure an engineer approves the roof framing as well as the sheathing.
2. waterproofing membrane - the lowest cost option I've found for this that has high effectiveness is 60 mil EPDM (rubber pond liner).  I also recommend reading "Stoneview: How to Build an Eco-Friendly Little Guesthouse" (New Society Publishers) by Rob Roy for additional suggestions for waterproofing membranes.
3. drainage/filter layer - I don't skimp on this because it keeps your soil medium up on your roof, even with heavy rainfall.  My favorite drainage layer with integral filter fabric is: Enkadrain 3615 (by www.colbond-usa.com) because it is easy to cut & easy to install, especially on curvaceous roofs.
4. growing medium (soil) - I have used everything from compost to an engineer mix of expanded shale & organic soil; they all seem to work well.  The only advice here is to be sure if you are using compost, that it is sterile, ie, that there are no active seeds (or you will be up there weeding like crazy) and if you use a mix with high inorganic content (like expanded shale) be sure it's mixed with at least also 60% organic soil (like sterile compost)
5. plants - I use ONLY sedums and other rock garden plants.  These are plants that don't rely on ground water, but instead have ways of storing rainwater (their leaves act like a cistern) or can pull humidity from the air for moisture.  Be sure to select plants that will thrive on your roof and in your climate, ie, whether your roof is in full sun or full shade and how much rainfall  you get in a year.  For recommendations on plants, see www.greenroofplants.com 

 

typical living roof detail

For additional information, including books and other resources, see my full article on Living Roofs at www.buildnaturally.com/EDucate/Articles/LivingRoof.htm

Clay Plastering Strawbales - SECOND COAT

I would like to address issues & tips for the 2nd coat of clay plaster on strawbale walls today. Note, I am assuming you are using clay plaster for all 3 layers of a 3-coat application. For tips on applying the 1st coat of clay plaster, see my previous post "Clay Plastering Strawbales - FIRST COAT". For information on finish plastering, see "Finish Clay Plaster & Wall Preparation".

GOAL for 2nd coat of plaster
The goal for the 2nd coat of plaster is to sculpt the walls into the desired shape.  The first coat created your amazing bond to the strawbales.  And your finish coat will create the texture you desire.  This second coat is where you create the shape you want your walls to have.  Your shaping/sculpting plaster is bonding directly to the first coat of clay plaster you applied, so the bond of that first coat is essential.  Since your first coat usually is lumpy & bumpy, you have excellent surface area to physically key your second coat of plaster to the first coat.

transformation from 1st coat (left) to 2nd coat (right)

In this coat of plaster, I care very much what it looks like...not how it feels, but how the shape looks.  I try to minimize or avoid cracks, I work sculpted areas a lot so they look exactly how I want them to, and I spend as much time as needed to shape the wall into something that is beautiful to me.  Then I'm well-prepared for a nice, even coat of finish plaster, where I can work on texture.

WALL PREPARATION for 2nd coat of plaster
1. Work any loose spots - I go around the dry first coat of plaster and make sure there are no loose spots.  There will usually be a wide, tell-tale crack if you have a loose spot at a strawbale seam, where the first plaster was not worked in well.  I also check corners, around windows, and the tops of walls, to be sure all the walls feel nice and dense and tight.

2. Make test plaster mixes - I make several test plasters and apply them directly onto the first layer of clay plaster.  What I'm experimenting with in my tests are the proportions of ingredients.  Since I use almost exclusively clay soils to make plasters, it means I'm using different clay each time, and each clay has different properties.  So I make test areas at least 24" x 24" in area with varying proportions of clay and sand, and I write my proportions directly into the plaster surface.  When the test areas dry, I look for the one that cracks the least, but that I can press into firmly with my thumb and it is not crumbly or dust, but nice and firm.

3. Wet the walls down - I can't stress this one enough, and as I mentioned in the post on 1st coats of plaster, this is the most common error I see...applying plasters over dry substrates!  I hose down the 1st coat of clay plaster the evening before I plan to plaster, again in the morning, again about 30 minutes before plastering, and then continually as the wall dries out over the course of working.  If the 1st coat of plaster is dry, the clay sucks moisture out of the 2nd coat of plaster, and causes the bond between new clay to old clay to pop apart.  When deconstructing plaster coats that have been applied to each other without dampening the substrate first, the two coats of plaster are quite distinct, and you can easily pry them apart in separate layers, like sheets of slate.  Similarly to 1st coats of plaster, I allow time for water to saturate the clay substrate, because a water slick on the surface will cause new plaster to slide right off the wall.

In order to maximize control over the shape of the walls as well as the quality of the plaster, I do the following:

SIFTING.  I use mostly clay soils to make plasters and there are often stones and large clumps in the mix.  So I sift clayey-soils through a 1/2" or 1/4" screen to break up the soil into smaller pieces.  Basically you want a screen that is slightly smaller than the thickness of plaster you intend to apply (otherwise stones will drag with your trowel against the hard 1st coat of clay).

PROPORTIONS.  I use sand & straw, and sometimes manure, to control cracking in this second coat of plaster.  The reason is because clay expands in volume when wet, which means it shrinks when it dries.  Shrinking clay can translate to cracks in your plaster.  Sand, on the other hand, does not absorb water and so does not increase in volume when wet nor decrease volume when it dries.  So having a high percentage of sand in your mixture helps to control shrinkage of the plaster, and thus cracks.  However, the clay is your binder, it holds everything together and onto the wall, so you need to be sure that your plaster has enough clay to stay sticky, otherwise your will end up with a dusty mess.  The exact proportions of sand-to-clay depend on the properties of your clay, but roughly speaking, I usually end up with between 15% and 30% total clay content, the remainder being sand.  (Note that this includes any sand in your soil, if you are using clayey soil for your plaster.)  The straw component helps to bridge gaps where cracks are likely to occur.  I add a fair bit of chopped straw (3" or less in length) to my second coat of plaster to provide ample structural integrity and I add additional straw when sculpting the clay or where I'm trying to fill in deep holes.  Finally, I use manure whenever it is available, and it is probably my favorite additive for plasters and cob.  The manure is both sticky (like the clay) and fibrous (like the straw), so you augment two properties of the plaster mixture with a single ingredient.

applying the 2nd coat of clay plaste

APPLICATION.  In order to control shaping the walls I use a fairly long (16" to 18") rigid trowel to apply this layer of plaster.  Because the trowel is rigid, I can push the plaster around easily and because the trowel is long, I can create a gently undulating, reasonably flat wall surface.  I find a short trowel does not let me see low spots in my wall surface as well, and I find a flexible trowel just follow the shape of that lumpy, bumpy first coat, so I save shorter, flexible trowels for finish plastering.  If you have a lot of dips in your wall that you want to fill, you will want to add lots of straw to your plaster so it has more structural integrity.  I also limit the thickness that I apply on any one day, and instead, fill deep spots in multiple passes.  Even waiting one day before adding more plaster will allow the first batch of fill to dry enough, and bond to the first coat below, to support more weight of a second layer.  Again, remember that clay is a liquid until it dries, and can only support a limited weight of additional plaster before it tries to flow off the wall.  If your plaster is slumping or falling off the wall, it is probably too thick (or your clay surface below is not adequately damp).

walls become sensuously shaped with sculpted elements

SCULPTING.  This 2nd coat of clay is also the layer that I sculpt into...including niches, wall reliefs, and any clay frames around truth windows.  For thick reliefs, I add a lot of chopped straw, making almost a cob-like mixture, I make sure my surface is saturated with water, and I build up slowly...perhaps 1" in thickness at a time.  If I'm feeling impatient, I use burlap embedded into the surface of the sculpting clay, and I use the burlap to bridge the thick new clay onto the existing wall surface.  (more on burlap below)

using burlap at window sills to prevent cracking

BURLAP.  I use burlap mostly as a preventative measure in places where cracks are most likely to develop, or where the additional strength of surface fiber will be a benefit.  I also use burlap to apply clay plaster to surfaces that otherwise are too slick for plaster to adhere to, such as wood.  So at windows, I use burlap embedded into the surface of the 2nd coat of plaster to prevent horizontal cracking along the bottom edge of the window sill, as well as at the joints between the jambs and the sill (and the jambs and the window head).  The burlap provides exceptional surface tension, and holds the clay together as it dries, so that it cannot crack in those vulnerable locations.  The important trick is that the burlap MUST be fully embedded into the surface of the clay, otherwise it is not bonded and you actually create a loose spot instead of a strong surface.

burlap must embed completely into the clay

I also use burlap where plaster meets wood, and I don't want the plaster to shrink away from the wood, wherever I worry about wide cracks translating into my finish coat, and wherever I want to plaster over a slick surface, like a wood post, any rigid foam, or any roofing felt.  I had one workshop participant declare "burlap is like magic!"  And I pretty much agree!!

leave 1/4" reveal at electrical boxes for finish plaster

ELECTRICAL.  Finally a quick note about electrical boxes...I work the placement of all electrical boxes while installing this 2nd sculpting layer of plaster.  I straighten boxes.  I pull them out if they are recessed too far.  I push them in if they are bulging way past the plane of my wall.  My goal is a level box that sticks out with an even 1/8" to 1/4" reveal from the plane of my 2nd coat of plaster.  Then I can run my finish coat of plaster right up flush with the electrical box, and the cover plates will fit on squarely and tight to the wall surface.  It's also not a bad idea to put a bit of tape over the screw holes to keep mud out.

I'd love to hear other people's experiences and tips!  So please feel free to add comments below.

Clay Plastering Strawbales - FIRST COAT

I would like to share a few tips I have learned through trial & error over many years for plastering with clay on strawbale walls. In this post, I address issues and tips for the 1st coat of clay plaster applied directly to strawbale walls. I address 2nd coats of clay plaster in my post "Clay Plastering Strawbales - SECOND COAT". For information on finish plastering, see "Finish Clay Plaster & Wall Preparation".

Goal for 1st coat of plaster
The primary goal for the 1st coat of plaster is to create your bond between clay and straw.  The goal for the second coat is to shape & sculpt the wall the way you would like it to look.  And the finish coat is where you achieve your textures and sometimes color.  The strawbales provide ample surface area for the clay to bond to, so I do not use any lathing or metal mesh or anything else that may actually get in the way of working the clay directly into the straw.  Instead, I work a sticky clay plaster directly into the straw surface.

1st coat of plaster is often lumpy & bumpy

Because the goal is coating the bales with a well-bonded layer of clay plaster, your first coat of plaster often follows the contours of the bales.  This means the first coat is usually not that pretty...but rather comes out rather lumpy & bumpy.  This is OK!  You will shape the wall with the next coat of plaster.  It is more important that you set up great contact with the strawbales so that the weight of all the plaster to come adheres well to the wall surface.  You can shape the wall a little bit with this coat of plaster, especially in wedged areas, like the cracks between bales.  But remember that the clay is a liquid until it dries...and its stickiness can only support a limited weight of plaster before is flows off the wall.  If you find the plaster is slumping, this is usually a sign that your plaster is too liquid or that you have put on too thick a layer and the weight is pulling it off the wall.  Once the plaster dries, it is bonded to whatever it is touching, so best to be patient, use a thinner layer, work it into the straw really well, and wait until it dries and is strong before adding more weight with subsequent plaster.

WALL PREPARATION for 1st coat of plaster
1. Shape the straw - this means trimming the walls as closely as you can to the shape you want.  Spending more time shaping the straw pays back in magnitudes of time saved mixing and applying plaster.  I also cut niches and identify any truth windows prior to plastering the first coat.

2. Install electrical - I find that it is much more challenging to install electrical boxes after you have plastered the strawbales, so I get this out of the way before plastering.  This also makes an electrical inspection more straightforward, if you need one, since you have not covered up any of the wiring with plaster.

3. Make sure your walls are tight - this means achieving a pre-compression of the strawbales before plastering.  If you plaster before the bale wall is compressed downward, then the weight of the plaster can cause the strawbale wall to sag, leaving an open gap at the top of the wall.  A gap can be filled in with insulation, but it's usually easier, less stressful, and cheaper to compress the bales first.  There are many ways to achieve a tight wall, starting with purchasing tight strawbales to construct with.  (The looser your bales are to start with, the more they will compress in place.)  I make sure the top bale in any wall is installed very tightly up against some kind of framing above (floor, trusses, etc.).  You can also use temporary straps to compress your walls.  I'm sure there are many other solutions, but the general goal here is that the more compressed your straw is, the less your wall can settle from the weight of the plaster.

4. Trim the straw - the trimmed side of a bale, with all of the straw sticking out perpendicular to your plane of plaster, is an easier surface to plaster than the folded "fuzzy" size of a strawbale.  So trimming your bales with a weed whacker, chain saw, hand saw, or whatever works for you, saves you time applying the plaster.  Trimming also gives you the opportunity to sculpt the straw surface to the desired shape of the completed wall, which saves you time mixing and applying plaster or cob-like plaster to fill in voids and shape your walls with clay later.

5. Fill in voids - this also saves you time later!  Unless you want your wall to remain lumpy & bumpy, I find it is the least amount of work to make sure that voids between the strawbales (and at seams with other surfaces) are stuffed tightly with straw or light clay straw before I begin plastering.  Otherwise you are making additional plaster or cob-plaster to fill those voids later.  I use handfuls of long pieces of straw, align them all like a rope, twist the rope, and then fold it in half.  This lets you make relatively compact bunches of straw that you can then push between strawbales.

6. Wet the walls down - I think the most common error I see is applying plasters over dry substrates.  I hose down the surface of the straw until the water drips off, and then allow the water to absorb for 20 to 30 minutes.  The straw should feel pliable (not prickly), but all the water you spray on should be absorbed (not creating a water slick).  If you have a water slick, the clay plaster will slide right off the straw and drive you crazy.  If the straw is dry, it has a tendency to quickly suck water out of your plaster, which can cause the bonded clay to dry too quickly, which can subsequently reduce the adherence of the clay to the straw.


TIPS for 1st coat of plaster
In order to ensure a fabulous bond of the first coat of clay to the strawbale wall surface, I do the following:

• high clay content - I used to try to control cracking in the first coat of clay by adding sand & sometimes straw, but this mixture is so difficult to apply because it is not as sticky.  So I have shifted gears toward a very high clay content, shooting for between 1/3 and up to 1/2 total clay content (the remainder is sand from the soil or added concrete sand).  I do not add straw to this layer, instead working the clay into the surface of the strawbale walls.  The high clay content means you will have shrinkage, and therefore probably lots of cracking, in that base coat of plaster.  But I find I am able to get a much stronger bond with the base coat if the mixture is nice and sticky, and you can easily address the cracking in the next layer of plaster.
• sift soils through 1/2" screening - if you are using site soils, I recommend to sift the clayey-soil through a 1/2" screen to break up the soil into granola-sized chunks.  This makes the plaster easier to mix, and you don't end up with large chunks in your plaster that are difficult to impossible to work into the wall.  You don't need finer screening unless you are troweling onto a hard substrate in thin layers.
• apply 1st coat with your hands - when I teach plaster workshops, I used to invite everyone use their hands or a trowel to apply 1st coats of clay plaster on strawbale, depending on their own comfort level with tools.  And invariably, someone with troweling expertise, would apply a vast amount of plaster on a wall, and it would look great, and then...it would fall off.  What was happening is that by using the trowel instead of their hands, they couldn't feel whether the clay was worked into the straw.  So now I always apply the 1st coat of clay plaster directly onto the strawbales exclusively by hand (or with gloves), and not at all with a trowel.  This way you can feel...with your hands...the tactile bond between the clay and the straw.  You can feel if the straw is loose, like at seams between bales, and you work additional clay into those spots.  You can feel if the clay is tight on the straw or if it shimmies like jello and is not bonded.
• really work the plaster into the straw - this is probably the toughest to explain in words, but basically, you want to work the sticky plaster onto the surface of all the strawbales, but also into all of the nooks & crannies between strawbales as well as the joints where straw meets other materials.  I use the palm of my hand as a trowel to apply plaster to the surface of the strawbales, and I use my fingers to kindof massage the clay into any loose spots between bales.  Once you have some sticky plaster bonded to the straw, you can add lots of straw to your mix, and use that heavy-fiber plaster to fill in any big voids.  The straw-plaster will stick nicely to the clayey-plaster that you already worked onto the bales.
• don't worry how it looks - the most important quality for the 1st coat of clay plaster is that the clay bonds well to the straw...it is not what the shape of the wall looks like.  That is not to say you cannot shape the wall with this coat of plaster, but the primary goal is the bond to the straw, not the look of the wall.

I'd love to hear other people's experiences and tips!  So please feel free to add comments below.

Shake Test

Video blog today, showing how to test your soil for clay

content, including worm test & shake test