Feedback on this Foundation Assembly
Long-time lurker, recent Prime member, and first time post-er. Zone 5A.
I am in the design phase of a prospective new build looking for feedback starting from below-ground with the foundation.
We are looking to build a single-story home on a slab that minimizes concrete, avoids styrene, and still maintains a continuous insulation layer of R10 under-slab, R20 for the stem wall.
Foamed glass board and aggregate seem like great options, though I do suspect the embodied energy may be considerable, given the kilning required, but we are building a house after all; energy required.
I am attaching a PDF but, here’s the gist of what I am thinking.
– rubble trench with bottom drain (frost depth ~40″)
– high slag/fly-ash concrete footer/stem wall on top of trench
– 6″ foamed glass board between stem and slab
– 6″ foamed glass aggregate under compacted earth slab
– 14″ panelized strawbale walls bear on stem, bridge over board to slab
– geotex under the entire footprint including trench
– poly running between aggregate and slab, wrapping under concrete footer, and back up the outside of the stem wall
Since this is quite literally the foundation of the whole project, I am going to work with an engineer on detailing, but figured I’d look for early feedback here.
Any all thoughts/questions/critiques are greatly appreciated.
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Welcome to GBA! I'm giving your question a bump, as I loath to think of you having an unsatisfying foray. I applaud your efforts to eliminate concrete and foam. I know Ben Bogie is a big proponent of foamed-glass aggregate for that reason, among others. He is using it for a concrete-free slab for a current project. Check out this video about the foundation wall system. Soon I will publish a companion post about the foamed aggregate slab. Also, this BS* + Beer Show episode is all about the product. It's impartial and informative.
Hey Kiley, thanks for the bump. That BS+B is actually what lead me down the FGA route! Looking forward to checking out that wall system.
Not a comment on the foundation - but the dowels (usually steel rebar) in the bales is out dated for site build strawbale walls.
Who is providing the panelized strawbale walls?
Thanks Tim, originally we were looking at doing infill with oak dowels, but now are hoping to go panelized.
Don't have a source yet, looking at Ecocon and Gryphon Panels from New Frameworks. Also considering building panels ourselves, but this is obviously the long row to hoe.
These guys are working on a strawbale panel system. They got an US EPA grant to work on it.
They also worked on a book with the California Straw Building Association https://www.strawbuilding.org/Straw-Bale-Building-Details
Thanks Tim, I've sent Verdant an inquiry, and I picked up that CASBA book when we began looking for property. It's a great text.
Where are you planning to build?
https://www.arkintilt.com/ has been featured in Fine Homebuilding. They used sand as thermal mass under the main floor.
What you can do with your foundation section really depend on your seismic design category and possibly wind design loads on the building.
Hey Tim sorry for the delay here.
We are looking to build outside of Cleveland, OH. Seismic is not a concern, fortunately. Not sure about wind loads, tho certainly nothing like a coastal or desert exposure. Def need to check that in the OH residential code