hempcrete extension over cob cottage
2012 Oxfordshire
hempcrete consultant | site training
The owner, architect and also self builder of this extension came up with a clever way of using stainless steel builders bands for diagonal bracing.
The extension is on top of historic cob walls. The builders bands will provide lateral restraint but will allow more flexibility in the structure than diagonal timbers.
This will allow the new build to move slightly as the cob walls adjust to their new load, avoiding differential settlement.
They were also very easy to cast hempcrete around.
This little concrete mixer did a sterling job.
Preparing the shuttering.
The corners should be cast all in one go for strength as should lintels.
This extension is built on top of cob (earth and straw) walls. The cob is flexible, creating an extremely stiff box on top might cause differential movement as the cob adjusts to its new load. For this reason the owner/architect used stainless steel builders bands for diagonal stability bracing. They do brace the building but allow slightly more movement than great big diagonal timbers. They are also extremely easy to cast hempcrete around.
Note the holes filled in where the spacers were, you can avoid these by removing t he spacers as you progress.
I love this detail, where half of the historic daub had to be removed hempcrete has seamlessly replaced it.
The hempcrete easily molds to the form of the cob walls.
