Re: SB: Re: CLAY SOIL

["j. gann" <jmygann@yahoo.com>]

I am also working on a foundation. Could you please
explain (SDM) the simplified design method.. What kind
of insulation is used in the FPSF and horizontal wing
insulation ?


--- "Robert W. Tom" <archilogic@yahoo.ca> wrote:
> 11/20/01 9:01:21 AM, "Cat c" <spotmb7@hotmail.com>
> wrote:
> 
> >Hello can anybody help me?
> >
> >I am planning to build a straw bale home next
> spring and was wondering what 
> >would be the best foundation to use for clay soil? 
> Would a slab on grade be 
> >the best choice (dig out the clay and replace it
> with gravel).  Take into 
> >account I live in Quebec, we have very long and
> cold winters and all the 
> >foundations in my area have cracked due to the
> frost.
> 
> Catherine;
> 
> I suspect that one of the reasons you've not been
> getting many responses 
> is because foundation design is very site-specific.
> 
> I suspect that another reason is because  "best"
> would be very subjective.
> 
> With regards to your stated choice, (Slab-on-grade)
> it would likely have to 
> be designed as a frost-protected shallow foundation
> (FPSF) and more specifically,
> a FPSF with an insulated slab, precluding the
> possibility of being able to use
> the Simplified Design Method (SDM)
>   (ie A FPSF with an uninsulated slab relies upon
> heat loss through the slab to 
> help keep the earth around the foundation from 
> freezing, allowing one to use 
> the SDF.
> 
> The problem (IMNSHO) is that such foundations
> require the extensive use of 
> not-very-Green and rather eXPenSive eXtruded
> PolyStyrene (XPS) foam insulation,
> putting it into the ground where it is readily
> accessible to ants (and termites
> in warmer climes) who love to tunnel into the stuff,
> turning one's foundation 
> protection and money into dust (literally).
> 
> Further, slab-on-grade foundations don't typically
> provide the bales with a good 
> separation from grade and should really have a more
> substantial upstand designed
> in (ie It snows and rains in Quebec. Non ?) . 
> 
>  An upstand in the order feet instead of inches
> would be more sensible... so by 
> the time one has thickened the edge of the slab and
> built a substantial upstand 
> on top of the slab, the amount of material consumed
> is approaching that which 
> a stem wall to below frost would have required
> except that a stem wall to below 
> frost wouldn't require the eXPenSive horizontal wing
> insulation that a FPSF 
> requires.
> 
> Of course, all of the above are generalisations
> which can be rendered inaccurate
> by specific design strategies, but close enough for
> horse shoes and hand grenades.
> 
> The idea of digging out the clay and replacing it
> with gravel may not necessarily be
> a good idea in some cases (ie if the site is near
> the bottom of a slope).
> 
> All that being said, I think that a Rubble Trench
> Foundation (RTF) would be worth 
> considering  (rendering my second statement
> incorrect).
> 
> RTFs , unlike monolithic foundations,  are
> inherently able to withstand the 
> destructive forces which frost activity can impart.
> 
> And that being said, if your clay is Leda clay
> ....I'd think  about  moving. 
> (Leda clay turns into a liquid under load (sp00ky
> stuff)  but on the bright side,
> MeatHook (who lives in Shawville PQ) tells me that
> it makes a dandy 
> earthen plaster.)   
> 
> 
> --- * ---
> Rob Tom
> Kanata, Ontario, Canada
> <ChaffArchiLogic@yahoo.ca>
> (winnow the "chaff"before responding)
> 
> Please visit http://www.theHungerSite.com daily
> 
> 
> 
>
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