Thread: perfect storm behind the wall?

Basement exterior wall, cmu foundation, the foundation wall had a cap of oak, running across the top. Client notice the heave between pcs and then mold. He took the cap off and opened the wall, very wet insulation. I do not see metal framing members, ever, so I am wondering that perhaps the metal might create more moisture due to location???
I don't know, took pics, recorded my visit. the basement was completely finished, the only holes in the vapor barrier were from the brad nails...that I could see..

could it be a perfect storm in the wall because of the metal...

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I doubt the metal tracks have anything to do with it. Metal tracks and studs are pretty common around here, see them regularly. I've also installed them abundantly over the years. Never come across any issues based on the metal. Whats the outside grading look like? Maybe a brad put a pin hole in a supply line along the wall.

Thanks Markus,

The lot is not on a great grade, bottom of two slopes, but that wall is not the bad side...snow we do get, come the spring no shortage of run off...and it goes around this home to get to culverts. This side is the best, and has a pardge coat and damproofing, which may not be working.

I called all of the drainage issue out when I inspected in January. For perspective, this was the first home I needed snowshoes for...

Thermal bridging of the metal top cap in contact with concrete.
Air space in behind fibreglass, condensation forming, moisture migration inward through concrete block.
No drainage layer cold side of insulation.

http://www.google.ca/url?sa=t&rct=j&...ng4brWwR79zwfA

i'm wondering why there is a vapor barrier. Any moisture transmitted by that wall becomes trapped there. Am I seeing that all wrong ?

Garry

In Ontario the building code requires the vp to be on the warm side of the insulation.
But that has been troublesome because in summer months the moisture moves inward
and becomes trapped on the inner side of the vp. In winter months moisture migrates outward.

BSD-103: Understanding Basements — Building Science Information

Basement walls should be insulated with non-water sensitive insulation that prevents interior air from contacting cold basement surfaces – the concrete structural elements and the rim joist framing. The best insulations to use are foam based and should allow the foundation wall assembly to dry inwards. The foam insulation layer should generally be vapor semi impermeable (greater than 0.1 perm), vapor semi permeable (greater than 1.0 perm) or vapor permeable (greater than 10 perm) (Lstiburek, 2004). The greater the permeance the greater the inward drying and therefore the lower the risk of excessive moisture accumulation. However, in cold climates or buildings with high interior relative humidity during cold weather, the upper portion of a basement wall may become cold enough that a vapour permeable insulation will allow a damaging amount of outward diffusion during cold weather. A semi-permeable vapour retarder or foam or a supplemental layer exterior insulation can be used in these situations.

Info-511: Basement Insulation — Building Science Information

much more here
Building Science Information

Looked at the links, ( great info. BTW ), and it's a delicate balance. Reminds me of tightening up a house so much by code that the code then requires vented windows so there can be4 some air transfer / breathing. It seems what is missing in the O.P. is the semi-permeable vapor barrier. The plastic vapor barrier in the photo has little to no permeability.

Here is another good link

CMHC research article Understanding Vapour Permeance and Condensation
in Wall Assemblies

https://docs.google.com/viewer?a=v&q...C0R2T4T_eXcRhw

Thankfully Ive read most of those links, now I am going to read the other half...Thanks guys