The plumbing and electrical have been roughed in, the furring strips have been installed, and last week 109 bales of wheat straw were delivered. It’s time to fill the walls in.
Light straw clay (LSC) construction involves lightly coating straw with clay slip(a very liquid muddy mixture) and packing it into wall cavities using temporary or permanent forms to hold it in place. The result is a highly insulative, sound proof, breathable and non-toxic wall. I’ve made significant study of the process but have very little hands on experience.
This week we’ve been experimenting with our process of making it and packing it into the walls. Note that light straw clay is also called straw light clay, light clay straw and slip straw. They all refer to the same thing and I’ll probably use all the terms.
Here’s a recap of the week/introduction to the light straw clay:
Here are some stills with more details:
Jean mixing up the clay slip
The clay slip is supposed to have the consistency of cream. This is a little thick.
The timber frame posts and beams will only be visible on the exterior of the cabin. On the interior they will be covered with ~1.5″ of straw light clay. To get the mixture to hold to the post I installed two 1/2″ dowels vertically on the post. The idea is that straw light clay with slip in around the dowels thus staying attached to the wall.
Moving the form up the wall, the dowels seem to do the job of holding the straw light clay in place.
The ~1.5 “of straw light clay will provide a layer of insulation on the post to prevent thermal bridging.
Installing plywood form to stud bay
One logistical item I need to solve is how to get loads of straw light clay up to the loft without having to haul it up a ladder.
Jean packs in the straw light clay
Shoveling in straw light clay
The forms can be removed immediately after the walls have been packed in
A couple of my cousins and my aunt came up from Houston for the day for a visit and I only got this one blurry picture. Thanks a lot camera
Jean insulating a beam.
There’s something very rewarding about removing the forms and seeing the straw pressed into the wall.
10 thoughts on “Light Straw Clay Construction: The Orientation”
What is Tom wearing on his head?
Great video. One question, why is Jean doing all the work?
What is the Thermal Mass difference between cob and straw clay slip?
Ocean and River were impressed by sight of the chickens
A welder's helmet for some reason known only to himself.
I've taken on a supervisory role. Congratulations to me
Fairly significant. Cob is 95 lbs/ cubic foot. Straw clay slip is 13 lbs per cubic foot
Is there any concern of the light straw clay being in direct contact with the timbers, in terms of the wood's longevity, or does it dry out and not become an issue? Did you consider running the light straw clay envelop around the exterior of the timbers, so as to keep them visible on the interior?
It dries out pretty quickly. Light clay straw is also vapor permeable so if it gets wet again it doesn't trap moisture in the wall.
Regarding the second point, I thought about it and the timber framing book I read recommends completely enclosing the timbers in cold climates. When I was designing the project I was concerned with maximizing support for my extended roof overhang.