Slab-on-grade instead of Pressure treated wood foundation

Margot Simonot Published: May 20, 2019, midnightLast updated: May 21, 2019, 9:26 a.m.

Allergic to chemically treated wood, CODE requires PWF on concreted slab before house can be built

Responses (1)

Mike Reynolds
Mike Reynolds May 21, 2019, 9:15 a.m. Reply

Hi Margot, 

Where are you building where code says such a thing? I don't think I really understand the question so I would need more information. A pressure-treated wood foundation (PWF) would be an alternative to a concrete foundation, and a poor one at that. The end result of mixing wood and moisture will always be rot. So building a house on wood buried in the ground is not something we have or ever would recommend. 

And a slab-on-grade is an alternative to a basement, PWF or concrete, so I'm not sure where you're being advised to mix a PWF and a slab on grade, or how to even do that. A slab-on-grade floor consists of concrete and insulation (radiant heating tubes, mesh and rebar of course) but not wood. A wooden structure would sit on top, above grade where it can dry properly. 

If you are chemically sensitive then there are any number of materials that may go into a home that might cause you health concerns. We built a LEED Platinum demonstration home (the Edelweiss House) a few years ago (on a slab) and we were careful to choose healthy building materials such as zero VOC paints and finishes, formaldehyde-free plywood for cabinetry, recycled quartz counters etc.

If you have chemical sensitivities then your foundation isn't likely the biggest concern (though as mentioned we don' like the idea of sticking wood in the ground), we would recommend carefully choosing all interior finishing materials to ensure healthy indoor air quality. Below are a few pages to read over, and again, please explain a bit better what you are being told about foundations and we can probably help you. We are in the process of building another demonstration house in Wakefield, Quebec, it is from a slab-on-grade kit. The manufacturer (Legalett) has over 2 million square feet installed in North America and they have never been refused a permit. 

Here are a few pages that may help you build a home with safe indoor air: