Clay/Straw infill and Wrap/Strap

I am considering using straw/clay infilled timberframe in a passive solar home in SW Montana, a very cold, dry climate. Can I effectively use a wrap/strapped exterior system like Jack Sabon illustrates in "Build a Classic Timber Framed House" with a simple stud wall infilled with straw/clay? Would it be better to have the whole wall be breathable? Say using 2.5" rough cut siding and no insulation exterior to the frame or using breatheable rigid insulation like rigid fiberglass? Anone familiar to this or recommendations?

What is 2.5" rough cut siding? Planks?

Some nice reading in the latest Timber Framing, journal of the Timber Framers Guild, covering your questions. If you are not a member you could jump on board and they will send it to you, for free.

I would suggest that you build a envelope wall a foot thick on the outside of your timber frame and infill that with light clay straw/wood-chip. Much easier than trying to infill, getting around all the braces and such. If you would like more information on how to build the "matrix" wall system please let me know. I would be happy to guide you in the right direction!

Thanks,

Tim

Tim-- I'm curious about the "matrix" wall system you mentioned. Is it a double wall with light framing? Guide on...

2.5" rough cut siding, just bevel edged and shiplapped 2x8 type planks or some such variation; a thick, rough wood exterior. Just an alternative to a vapor sealed type synthetic wall or multi layer 1" planking, just trying to use as much local rough cut as possible.

For air penetration, rather than a shiplap you may consider using a tongue and groove on the planking, with the tongue facing up so water doesn't collect in the groove. This just gives you 1 more bend for the air to get around. Also, a tongue and groove is easily sealed with tar or some such (I would not recommend silicone). See if you can find some pine tar for this (it will be hidden away inside the groove) or if you can't asphalt will work.

2 or 3" plank siding and/or infill is very common in Switzerland, whose building style I have been studying, so I have learned quite a bit about how to execute it.

One traditional Swiss wall system is probably very similar to what you are thinking, a wall infilled with 'lehmbau' which is often a straw/clay setup, or may just be clay. The exterior is covered with thick planking nailed onto the timbers, and the inside is usually covered with wood paneling, but in a more utilitarian setting may be covered with reed and plaster. The timbers are thus totally concealed. Alternately, the infill may be random stone mortared with clay or lime.

Devin - if you go to my blog http://trctimberworks.com/category/blog/natural-homes-blog/ and scroll down a bit, you can see the whole process!

Happy reading!

Tim

Hi Tim,

I enjoyed reading your blog, I used to plant trees for Mart Resources years ago, so I am familiar with your area, would love to come for a workshop.

I have been interested in building a post and beam cabin for many years, and insulation is what really bothers me. I have a lot in the Gaspé Peninsula of Quebec, and I want to build a cabin with local timer, shingles, and the last thing I want to do is to have ISP trucked 1000 kilometers!

I live in japan, and I have been fascinated by the clay infill buildings I have seen. I use to live in a house that was a timber frame infilled with clay and straw on bamboo lattice. I now live in a modern japanese timber frame that has lime plaster as siding and finish inside the house, and I just love it.

I took a timber framing workshop this summer, and I am planning to build a cabin on my lot. My lot is on the Saint Lawrence River, and it can be wet and stormy, so I would like to to do straw and clay infill, and cedar shingles on the outside.

Do you know what is the insulation property of clay and straw mixed as opposed to straw bale?

The thickness of the walls of straw bales bother me and keeping dampness away, seems to be an issue. Have you build anything with infill of straw and clay?

Thank you,

Serge