Monday, November 16, 2009

Straw walls and lime plaster

The building season is pretty much over now and the house has come together pretty fast. Sorry I haven't been posting to this blog as frequently as I would like. I was busy working on the house, then we had a few weeks of low to no power so my internet access was limited.

We had some great weather in early November, which made plastering much more pleasant. It worked out well because the few weeks before the good weather, we had a lot of rain, and fortunately most of the work was baling the walls under the tarps. Of course it was pretty gloomy working under the tarps on such gloomy, cold days. The baling took a lot longer than expected. The lower parts of the walls went up fast, but the tops of the walls required quite a bit of notching, which is time consuming work.

The cistern hole was dug before I started the baling. Here is a picture of Bear and Zane perched on the second floor watching Luke work the backhoe. Zane is a funny kid. At two years he's already obsessed with big machinery. I wonder how many two year olds talk about wanting to see a skid steer or a front end loader. I'm always amazed at the precision of the guys who operate this big machinery. He worked straddling a sapling cherry tree and came inches from the framing of the house, but I never was nervous.

Right after digging the hole they plopped the cistern down in the hole and filled it most of the way in.

Like I said the baling seemed pretty slow despite the fact that we designed the house with timber framing instead of stick so that we would have less to bale around. But I guess thinking about it, considering how much the bale walls make the house seem like a house, it went from being open to being enclosed in a relatively short time. This was the bale knife we used to notch the bales so we could fit them around the posts and beams.

To bale you have to start at the corners and you complete one course at a time stacking them up like bricks. To stabilize the walls, I secured the bales to the posts at each course as the walls went up. Some parts were pretty tricky. Around the windows and the top course of the first floor were the most time consuming spots.

This is a picture looking down at the first floor north wall through the stairway. In the process of baling you have to make many short bales, which involves retying a bale to form two smaller bales. This takes a lot of time too.

The front door and the first floor walls almost complete.

Onto the second floor. About this time it got really cold and rainy and dark working under the tarps. Some people don't worry about getting rain on the sides of the bale walls because the rain can't really penetrate past a half inch or so, so they don't bother with tarps. It's important to keep rain off the tops of the bales though because then it can soak in deeper and start to rot the bale. At this point it's really hard to get the moisture out of the bale and it will keep rotting.

Before I was done baling the second floor we prepped the first floor for plaster. This involved weed whacking the outside of the bales to smooth them out for the plaster application. Some people don't do this step, but I found it helpful in preventing the plaster from being flicked up in our faces by loose straw when we were plastering. After trimming the bales, we covered the wood framing with burlap and metal lathe and installed flashing as a plaster stop at the bottom of the wall on top of the foundation. This protects the bottom of the wall at this seam from water infiltration.

Because of the impending cold weather, I decided to use some portland cement in the plaster so that it would set and be protected from freezing temperatures. Straight lime plaster takes a few weeks to set and is vulnerable to freezing, which basically ruins it. Some feel that cement prevents lime plaster from setting properly and you end up with a weaker plaster in the long run. I plan to use straight lime plaster in the remaining coats.

This was a plastering party we organized to help us get a lot of plaster done in a short time. Cory (in the grey hat) , a work exchanger who helped out for the month of October, took part in this plaster party. He also worked on the baling with me, and the light clay straw insulation on the south wall.

Mary Beth plastering the east wall. Plastering is kind of fun, but I do think it's more fun not to be working with caustic substances like lime. Unfortunately earthen plaster doesn't hold up as well in our climate and takes more maintenance.

The south wall was insulated with light clay straw since it will be getting most of the sunlight. I love the way light clay straw walls look when they are exposed like this. I wish I could just leave them that way. I will eventually side the south side of the house so the plaster ended for the season once we'd made it around three walls.

It's a really nice view out the windows on the south side--the garden, the pond, and across the gravel road, a green hillside pasture and cows.

I was relieved to get the plaster finished, and after that there was just a little bit more to do on the light clay straw. I finished plumbing the cistern and filled in the hole, so it will be ready to be hooked up to the sink inside next spring. I put in the last windows and covered up the gable ends for the winter. Now the only thing left to do is put a door on. If I get the house inclosed I may continue to work on some stuff inside over the winter. I'm going to be looking into buying the power system, too.

The chickens moved over to the Ironweed kitchen coop for the winter. I built them some nesting boxes. Just before I moved them over there, they were in the chicken tractor in the garden. I went out one morning and found an egg on the ground. Since then the eggs have continued to come in greater numbers all the time. I think there are about 4 hens laying now. I was also happy to see how the fall planting of broccoli, carrots, and beets did so well this year.


Anonymous said...

Hi Dan, my partner and I live in Snug, Tasmania, Australia and have journeyed into light clay building feeling a bit like pioneers here in Tassie. There are no examples of this process and no teachers here. all has been going really well - we've been really enjoying the process and loving involving friends and family in it. We've been looking for more information regarding what sort of earth plasters to use and have been experimenting a bit. Can you please give us any clues as to how many coats, etc? We are planning to use a clay, sand, straw mix inside and to add lime to the exterior mix. Can we plaster the interior when the wall is still wet if we wait to plaster the exterior until next summer? We would be grateful for any info you are willing to part with.

Dan said...

Hi Cal,

As far as how many coats of plaster. I've usually done three, and this is what I've found in most books. A scratch coat, which keys into the straw as much as possible, a second coat, to build the thickness of the plaster, and the final coat, which is burnished to a smooth texture. The lime plaster is usually applied with a trowel, though we used our hands for the scratch coat. For the earthen plaster people at DR usually just apply it by hand. I would wait until the light clay straw has dried before applying the plaster. There are many books out there that give details on plaster proportions and application. Serious Straw Bale is a good one. Mixing proportions really depend on the consistency of the clay you are using and take a little experimentation with test patches to get the right mix. Hope this helps.


Anonymous said...

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Heather said...

Hello Dan,
I have been scouting my countryside, North Texas, for straw bales and the only thing I've come up with this far is 4x4x8 foot massive bales. Seeing that you have had a bit of experience with retying would you ever consider retying these monsters into a few 4x4x1.5 foot "sheets" so to speak?? My imagination sees alot less joints and such.... Heather

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