[Greenbuilding] Radon question

[RT]

On Mon, 02 Apr 2012 17:22:43 -0400, Clarke Olsen <colsen at fairpoint.net>  
wrote:

>
> A ground floor room tests positive for Radon
> Big (1/2") joint between foundation and slab is the likely source.
> Should I:
>                  a) seal-up the joint with non-shrinking mortar?
>                  b) seal it with expanding foam? With caulk?
>                  c) arrange some form of fat baseboard vent?
>


I don't think that non-shrinking mortar would provide a very effective  
seal because although the mortar *might* not shrink, the slab is almost  
certain to shrink (and expand) in response to temperature changes. The  
mortar being incompressible, could possibly result in cracks in the  
foundation walls or buckling of the slab if the slab expands (ie if the  
slab is heated).

Similarly, cured expanding foam would not be able to expand to provide a  
seal when the slab contracts.

A good caulked joint might consist of cleaning out the joint to a depth of  
~ 3/4 inch, taking care to remove all crud from the surfaces of the wall  
and slab edge so that caulking will have good surfaces to which it can  
adhere and then inserting a slightly compressed, flexible neoprene gasket  
or closed-cell foam backer rod, followed by a well-formed bead of caulk.   
(I just did a quick Google to see if I could find an image of a properly  
formed joint but no luck in the first two pages of hits. If you can't find  
ay=nything on your own, let me know and I'll send along a sketch)  (And  
"yes" proportions and shape of the bead matter, in determining  
serviceability,longevity and effectiveness of a caulked joint.)

Fat baseboard vent ? Nyehhhh...

=== * ===
Rob Tom
Kanata, Ontario, Canada

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