Recently my friends asked me for advice on building a small straw bale building (a garage with a living space above). They asked me how it will compare, timewise, to conventional framing. The answer: it will definitely take longer. They will save money on materials (some) but it will only be worth it if they really want the extra insulation value. They do, and they want to try building with bales as a test run for a future house. Also they want to use post and beam anyway, which means they need some kind of secondary wall system – for this reason, and aesthetic reasons, bales and timber frame go well together. I wanted to give them a good idea of what they were getting into, so I compiled a step-by-step checklist of exactly what you need to do to build an infill straw bale wall.
Here it is:
Bale building checklist
Before bales (after foundation and basic structure)
- Roof must be finished. Really finished!
- Bale curbs installed
- Top plate (never OSB – plywood OK)
- Framing for doors and windows
- Pre-hang mesh if / where needed
- plan air sealing details which may need to go in before bales
- Electrical?
- Bracing for windows or guides for bales if needed
- Scaffold? Set up before baling if possible. Plan tarping accordingly
- Tarping (tarping that rolls up can be nice). Attach to soffit area, not facia
- Get bales
Bale install
- Check bales for moisture as you go
- Pre-fill voids where corner of bales meet
- Notch / install bales. Check plumb as you go. Tie into posts as needed (frequent)
- Cut curves / angles for windows – can be done before or after bale placement
- Dipping bales? Need to pre-mix clay slip and mask finished wood
- Straighten walls / weed whack if not dipped
- Stuff all voids / check stuffing everywhere
Plaster Prep
- Cover all wood that will be plastered with typar / tyvek,
- Lath over wood & typar, hanging over bale transition by 1.5 to 2″
- Lath over air sealing materials
- Tenax mesh / stitching (recommended if not dipping bales)
- Flashing completed everywhere plaster will meet
- Plaster stops?
Plastering
- Process site clay?
- All materials and mixer on hand
- chopped straw (save from windows)
- Make wheat paste where needed
- Mix
- Apply scratch coat inside and out
- wait for drying / curing (1-3 weeks earth / 3 weeks lime / 1 day cement-lime)
- Finish coat in and out
- De-masking / clean up / detailing
- Caulk joints
- Crack filling (minimal with earth / more with other plasters)
- Paint
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