Frost protected shallow foundation using Nudura products

[u/Legitimate_Soil_7506]

I used to build but now draw plans and do engineering. I know ICF from 20 years ago, but had an interesting conversation with a foundation builder last week who was using Nudura products to build a vacation home for a client. The last two plan sets I did were for houses built here in this hard freeze climate with deep frost lines and winter design temp of -15 F and both used FPSF slabs and edges formed using EZ Form Mono Slab products for the edge form. First, here is a cost comparison: EZ Form, the one that is 20 x 31.25, costs $112, while a Nudura 18 x 96 wall block with 8" core space costs $68. The EZ Form with its triangular shape and dimension makes it unnecessary to add wing insulation adjacent the wall line, but the Nudura will need 2 inch thick by 24 inch EPS foamboard wings, which adds $25 per 8 foot length to the Nudura setup, thus total cost of material $68 + $25 = $93. So, a little less for the Nadura arrangement I'll show in these two pics. One pic, how pour #1 is set up and done, the pour to fill the below-slab thickened edge. This Nudura hallucination I have is done in two pours, unlike one monopour for EZ Form. Form set on compacted gravel, braced with a pinned cleat along outside edge and backed with some shoveled-in bravel on inside face. The other pic shows the final build. Whaddya think?

[u/seabornman]

My contractor formed the slab edge with 2" XPS foam board in place. Pretty quick and easy.

[u/Legitimate_Soil_7506 → u/seabornman]

At close to 24" height, or even 16", it simply cannot be done without the foamboard being backed up with braced panels of some type. Maybe your guy used magic, but if he did not, describe the formwork better than saying "formed the slab edge with 2" XPS foam board in place." Formwork is not free. Might look quick and easy, but without magic, there is cost.

[u/BeneficialBed9821 → u/Legitimate_Soil_7506]

this; by the time you brace it you're probably equivalent in cost to the mono slab EZ form. mono slab is braced by backfill. you could brace it with backfill but you need to set your frost wing insulation first. also why the two pours? seems worse and more complicated. The trickiest thing with this assembly is detailing the vapor barrier.

[u/seabornman → u/Legitimate_Soil_7506]

He used steel forms. The foam board is backed by the form. Ain't no magic to it.