[Greenbuilding] Earth-berming an existing home

[Alan Abrams]

>
> Mainly I agree with Nick - you're trying to make a retaining wall out of
> something that isn't.  You've got this little transition where the CMU
> foundation wall meets the wood wall, which retaining walls never have.
>  Retaining walls are continuous from above grade down through to the bottom.
>  I'm guessing that transition is a hinge point, and if you put enough
> pressure on that wall it'll buckle at that point.
>
> I don't even like Nick & Rob's ideas of building a wall next to the wall. I
> just can't believe you wouldn't discover later that at some point it got
> wet, didn't dry fast enough, and rotted everything out.  And don't you live
> in a fairly warm and humid climate?  Wouldn't you end up with condensation
> on the inside of the brick from the moisture vapor from inside the house
> combined with the cooling effect of the concrete/dirt outside?  Ick.
>

a retaining wall adjacent to an existing structure needs to be designed such
that the base of the retaining wall is low enough so that the surcharge does
not exert additional soil pressure against the the existing wall.  some
jurisdictions require that bearing for any new substructure within 5 feet of
an existing basement must be as deep as the existing footing.  this to me is
overkill, but good practice is to keep the new bearing lower than the angle
of repose (which varies with soil type) projecting up and out from the
original footing.

Further, a single tall retaining wall requires a great deal more mass and or
reinforcement than a series of low walls, terrace fashion.  A retaining wall
greater than 30" high also may require a fully equiped guard rail, something
that can be expensive and visually intrusive.

AA
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