[Greenbuilding] Radon question

Clarke Olsen prismoidal at gmail.com
Mon Apr 2 18:59:52 CDT 2012


Thanks - I hadn't considered slab movement (tendency to think of concrete as, well, cast in concrete),
but of course everything moves. Especially if they turn on the heat...
Clarke Olsen
373 route 203
Spencertown, NY 12165 
USA
518-392-4640
colsen at fairpoint.net




On Apr 2, 2012, at 7:14 PM, RT wrote:

> 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
> 
> < A r c h i L o g i c  at  Y a h o o  dot  c a  >
> (manually winnow the chaff from my edress if you hit "reply")
> 
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