Light Straw Clay Construction: The Orientation

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.