What's behind my walls?

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Posted by: from Toronto
3/5/2017 at 2:32:26 PM


Our house is probably around 60-70 years old. We're renovating a basement room that currently has wood paneling attached directly to strapping (no studs!). I pulled off a few panels and there seems to be a buildup of whitish/yellowish chalky material on whatever is between the strapping and the outside wall. It comes off very easily with a damp paper towel, or even dry. The original plan was to extend the strapping, put better insulation in, and then cover with drywall.

Questions: what is this buildup? It's not directly on cement/concrete so I don't think it can be efflorescence. I would have imagined mould to be harder to remove. Is it necessary to remove all this stuff before covering it over?

Thanks! (I'm a newbie, so any explanations would be super helpful.)

What's behind my walls?
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Steve from BDR Construction in Kanata
Date/Time3/5/2017 at 4:01:00 PM

It looks to be calcuim .. very common with cinder block foundations. It's an indicator that water is getting in. Having an air gap at the wall will help.

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Date/Time3/5/2017 at 4:18:56 PM

Calcium build up to show past water damage. Take off all strapping fill any obvious cracks with an epoxy and roll on bitumen on entire basement walls then frame not strap add vapour barrier and insulation and drywall. If your going to do it do it right.

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Robert from ElecTriLight Ltd. in Oakville
Date/Time3/5/2017 at 4:46:06 PM

Calcium buildup, showing wetness and possibly mould. Use good quality dust masks and remove as much as the material as possible and let the bare brick dry before closing it in again. There are many methods of preventing this from happening again, but it seems to be more of an exterior problem that needs to be rectified to prevent it from happening again.

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Date/Time3/5/2017 at 5:28:01 PM

The white stuff is calcium buildup you can mix a solution of javex and water to scrub it Off. I suggest you remove all the strapping and paneling. Frame new walls with 2x4 and keep a one-inch separation away from the concrete with the backside of your 2x4 wall 1 inch air space.

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Date/Time3/6/2017 at 8:06:06 AM

Hi Ed,

Yes, it is a form of mold, calcium build up. A mild form , but you do need a min. 1" air space between your block wall and your new 2 x 4 finished wall. You must have a bit of air flow as to lessen the chance of moisture build up behind the wall. If you are going to strip it all out, painting your concrete wall wouldn't hurt either.

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Aaron from The Reno guy in Onoway
Date/Time3/6/2017 at 9:34:17 AM

I agree with the other comments.

It sure looks like calcium.

Strip everything and look for the cracks !! Inject with epoxy ( see u tube video for crack repair ) or a cheaper alternative but not as good would be hydraulic cement. Then re frame with 2 x 4 with a 1" air gap.

Insulate and poly. Don't forget to use pressure treated for you bottom plates and use acoustic seal on your frame !! Again see u tube videos for instructions.

Good luck.

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