A flood forced the removal of the bottom 2′ of drywall, so I decided to remove the rest of the wall and upgrade insulation, especially at the rim joists. I intended to use spray foam, then I had a distinct memory of previously reading Dana Dorsett and Martin Holladay both writing (in comments I can’t now find) that vapor barriers are a “no-no” (Martin’s term) in a basement.  Does that mean closed-cell spray foam should not be used in a basement?

 

My house is double-brick, 110 years old, in Toronto, climate zone 5. If there was spray foam, could any moisture/vapor that comes in from the outside, thru double-brick, dry to the outside, thru double-brick? (No weepers – built before weepers were used.) Or would moisture get in more easily than it gets out, especially on a side that doesn’t get sun, meaning the area stays wet?

 

I ran a garden hose on full for 20 minutes in each of several spots, despite there being an overhang which means rain virtually never gets that close to the house directly, and every half hour I checked paper towel I had around the interior perimeter. No detectable wetness came thru. But the fact that the old white paint came off below grade (sometime in the last __ decades) suggests vapor drive inwards or outwards made the brick interior surface wet at least at some point in the past, and perhaps still does.

 

I also read that spray foam seals brick so causes spalling. (I was told if I spray foam brick it will cost tens of thousands of dollars of damage.) Conversely I also read that sealing brick stops spalling. I guess you want to stop water getting in, but allow vapor to get out.

 

Do you know if it matters whether my mortar is lime mortar or not? (One person presumed it was, based only on the age of the house, but they assumed modern mortar was stronger than my bricks, whereas my bricks seem-to-me stronger than not only modern mortar but also modern bricks.)

 

Is it safe to spray foam a double-brick basement?   

 

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I also considered using rigid foam, with spots of adhesive attaching it to the brick, with spray foam at the perimeters.  That would have the same vapor-trapping effect.

I also considered using Dricore Smartwall, or otherwise using rigid foam but leaving a gap between the brick and the foam.

The flooring is vinyl plank with nothing below the plank, so if water does descend to the base of the wall, I’m not sure it will dissipate, but I would guess imperfections in the concrete base would allow for vapor to move.  The 6’0″-6’2″ ceilings are so low I’m reluctant to add any insulation or air gap below the flooring.

 

Thanks!