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One of my clients has a basement room which has been suffering from mold and mildew for some time (nothing new here).
Today, we tore out the baseboards and drywall to find damp and mildewed fibreglas insulation, as well as studs totally rotted at the bottom; plates shot as well.
Now, it’s obvious that moisture has been penetrating the block walls behind this framed wall for some time, and I know how to handle that problem. The problem I’m not sure about has to do with prepping the block wall for Drylock or Thoroseal (I can’t do anything about the exterior of the block wall due to existing patio and stone-walled planting beds).
You see, since whoever the “contractor” was who built this addition apparently didn’t dampproof the exterior of the foundation prior to backfill, they smeared dampproofing on the INSIDE of the block before they built the stud wall, then installed fibreglas batts which stuck very nicely to the tar.
We were able to remove all of the
fibreglas with wire brushes and a stiff broom, but I’m pretty sure I’m gonna have to remove the tar before I can proceed with any kind of waterproofing paint product. Thought about using a high-pressure washer to try and remove the tar.
What say you ? Anybody been down a similar road before ?
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Hi Jay,
I was holding back in making any comments on this one hoping that someones else would take the ball and run with it.
This is one where you should contact the manufacturer of the product you want to apply to the surface, for information as to what they recommend for the removal of the tar off the block surface. The warrantee will be affected by any residues on the blocks from either the tar or the chemicals or diluents you use to remove it with.
For the benefit of your credibility on this little job, cover yourself with the recommended procedures not to void any warrantees and leave you liable.
Sorry I couldn't be of any more help.
Gabe
*Thanks, Gabe.You listed pretty much what I have planned so far. I've talked with a couple of dealers and searched UGL's and Thoro's websites, as well as a couple others, but I'm not really getting any "informed" advice, if you know what I mean.I figure the tar's gotta come off, unless I can find a bituminous-based waterproofing product to recoat the wall. No luck at all with that.What do you think about rolling on a couple of coats of new dampproofing and then sticking t&g styrofoam insulation board to the wall, then sealing the foam-to-floor joint with a good caulk ?I'm thinking that one over.
*Hi Jay,Technically you would be hiding the problem behind the styrofoam "curtain" but not solving it. (Last resort)Diesel fuel will desolve most of it and the remainder can be removed with a steel brush attachement on a power grinder. Clean the remaining surface with a neutralizer like tsp cleaner.On commercial work, I have come across areas that had tar like coatings that had to be removed. However, it was exterior and I had no worries about applying other coatings. So we sandblasted the surface. This is not always practical, inside a residence.Gabe
*Okay, not my field, but had a similiar problem recently on a local church.Just so I understand, the waterproofing on the interior wall will stand up to the head pressure exerted on it through the wall? I have heard from several people that Thoroseal will fail in this instance. Is this correct, according to your experience?Also, would you give me Thoro- webpage. Please.
*Here's the url I used to check on Thoro products: http://www.hsc-ss.com/0.asp?ID=1it's not a Thoro website, but they did have a pretty "thorough" (sorry, couldn't resist) spec and data section
*Thanks for the comments Fred. You brought up something we began considering today.After going back to the jobsite today (after a couple days of steady rain here) we found that 98% of the block wall was actually dry, while there was a small amount of standing water on the floor near the walls for about 8 feet either way from the corner.Upon closer examination of the wall, it appears that the slab floor and footing may have been one level pour, with the block wall laid right on the edge of the floor slab (man, I hope there's a keyway or some rebar in that wall to hold the base in place).It looks like the bulk, if not all of the water penetration is, apparently, from water which runs down the exterior face of the block wall until it hits the small ledge of footing, then migrates under the block wall through the mortar joint.This sitting water then wicked itself up the framing, insulation and drywall.So, what I think we're going to do (after the fans dry up the dampness for a couple days) is use an EPDM membrane glued to the block wall and coved down and glued onto the first 3-4 inches of the floor.Then, attach t&g styrofoam insulation boards to the block, followed by a covering of 4 mill plastic, also run out onto the floor.Then reframe the walls with a pair of treated bottom plates (separated with a strip of plastic), no fibreglas batts (we got styrofoam), then new drywall (MR for the bottom sheets held up off the floor).Comments ?