fixing crumbling mortar around blocked in basement window

12 years ago

I have tried finding some solutions to my problem in this forum and while I have learned so much about how to approach my basement finishing, i cannot find any reference to my specific problem. If you can help I would really appreciate it! FYI we live in Minneapolis!

We removed all the drywall from our what we thought was finished basement, which we started because we found some mold along one of the baseboards. As we began tearing away the wall we found more mold, growing on the drywall and 1x2s which they were attatched to. The house was built in 1960..there was no insulation, some vapor barrier in random places, and lots of rotting wood! Behind one wall we found a window which had been filled in with cement blocks, to accomodate the deck/patio behind the house, and the mortar around these blocks is crumbling and missing in places. It has been leaking, there is evidence of water stains running down the wall.

We have never had pools of water in the basement, but did see dampness in a few spots where the wall meets the floor in the back corner and wall of the house after a big spring rain since we have removed all the walls. We have graded, fixed drainspouts, installed a closed interior drain system and have an additional sump pump in the center of the house which was original.

We plan to either use xps or spray foam, as repeatedly suggested by Worthy...thanks for all the tips!

I want to patch this window area properly, and make sure that it does not leak before we begin finishing the basement. In addition to the leaking, there are a couple of areas missing mortar at the top where I can actually see daylight. The top line of the blocks seems a bit lower than the rest of the basement and I wonder if it was sealed properly to the exterior. The way the deck and brick patio are built prevent us from accessing this area from the outside.

For the window area repair, we have some ideas...spray foam, hydraulic cement, caulking...but I wanted to ask the experts before we start. Can anyone head us in the right direction to make sure this old window opening does not leak!

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Comments (5)

worthy
12 years ago
Concrete and mortar are porous materials--more or less depending on the chemicals and aggregates used in making them. So you can never use concrete as waterproofing, but only as a way to slow bulk (liquid) water.

Remove the crumbling mortar and repoint with a new proper "mortar mix" available at any hardware/big box/building supply centre. If you can access the blocks from the exterior, you can either dampproof them with asphalt cutback or waterproof them with Platon or similar plastic membranes. It wouldn't be surprising that the POs filled the window but didn't take that extra vital step.

There are crystalline waterproofing materials that can be effective from the inside, but I believe they now come in mostly industrial sizes and the preps using sulphuric acid are not a diy job.
janeskitchen
Original Author
12 years ago
Thanks Worthy,

You suggest mortar mix - not hydraulic cement, can you tell me why? I read about Hydraulic Water-Stop Cement by Quikrete.. any thoughts on this?

http://www.youtube.com/watch?v=WJM1537rp8s

Also, we can't access the exterior without tearing up the back deck and brick patio.
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This could be a serious structural problem that won't be fixed by patching and it would be wise to have a structural engineer (or at least a specialist who doesn't have a financial interest in the outcome) look at this now. If you patch now and it doesn't resolve the problem, more damage could occur that would make the situation more serious and more expensive to fix. Maybe it will be a fairly easy fix; but, if it's not, now -- not later -- is the time to find out. In an extreme case, a deteriorating foundation wall can result in a house settling, things getting out of plumb, cracks in walls, etc. Better to prevent than fix...
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First, try to ascertain where the water table is. Just because you're on a hill doesn't mean the water table isn't high. If the water table rises above your footings at any point, an interior system might be indicated. That's because water could be coming up through the slab or at the joint where the wall meets the poured footing. If the water table isn't that high, the only sure cure would involve excavating all around and using one or more of a number of different waterproofing products. These include spray-on membranes, bentonite, plastic bubble membranes, peel and stick and crystalline products. If there's a surface water problem, yes, swales might be helpful. But before that, look closer to home. Are your eavestroughs clean and functioning? Where do the downspouts exit? They should be sending water at least 10 feet away from the foundation. Is there a good slope down from the foundation to surrounding soil. I've seen many homes that sit in a depression--either because the original builder put the first floor too close to grade, or subsequent owners altered the grading. Not to mention the gardening types who load up on thirsty plants next to the foundation and water away like crazy. Next time it rains, go outside and check what's happening. ******* Mildew grows on my shoes in the closets upstairs, and my clothes have a musty odor. This is a separate problem and very likely the result of inadequate insulation on the closet walls. So moisture condenses inside--or even on--the interior walls during the winter. You can usually solve this problem by keeping the closet doors open during winter or providing an additional continuous source of heat. It's a reason to avoid placing closets on outside walls of a home, and especially corners where three and four stud framing cuts the R levels drastically. This post was edited by worthy on Sun, Mar 17, 13 at 16:49
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Thanks for your advice! The concrete was actually my idea (haha). The contractor suggested putting flashing around the foundation and then adding soil to grade away from foundation. I asked about the concrete because it seemed like a more permanent and waterproof solution. He's coming back today for a second look to finalize plans and I will ask him about just doing the flashing/grading and possibly a drain around the back perimeter (which sounds like a good idea, anyway). I feel we have to remove the deck and fill in that room because it's so horribly constructed (a deck constructed on top of an open hole in our basement, with just foam insulation separating our house from everything outside? insane! there's no door between our house and the basement, btw). The deck is also rotting from being exposed to so much rain and never being cared for, so it's an eyesore anyway. We've had two other companies come out-- there aren't many options around here. One were total shysters who just wanted to put plastic sheeting on the inside of our BRICK foundation and force the water to run behind it into an interior drain (while growing mold and ruining the foundation)---SO stupid, and for almost the same amount of money as actually fixing the problem. The other could only do a vapor barrier in the crawlspace and install a drain outside. The one we're working with now can do anything we need and is the only company like it around here. Switching to flashing/grading on the sides sounds great (while keeping the concrete patio)-- I'll ask him about that today. It would be really nice if we can get the cost to $5,000.
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Thanks for the suggestion! I checked them out but they seem to be for different applications than my basement windows. Mine have to be mortared in. I was just concerned that if the contractor used silicone instead of mortar for the installation, it would not be as safe. I have heard that if they are installed with silicone around the outside of the unit, it can be cut and and the window removed. Thanks again!
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worthy
12 years ago
If you're a really quick worker, you might get it done before the hydraulic cement becomes unworkable. Depending on the formulation, hydraulic cement sets in three-10 minutes. However, since this is only a "leak" because there is no mortar to begin with--not a crack or hole in otherwise solid material--I'd personally use conventional mortar mix.
brickeyee
12 years ago
Be careful with hydraulic cement.

It is designed to expand when setting to seal cracks, but in softer material it can produce new cracks form the expansion.

There are even high expanding grades that are used to break up concrete (drill holes, fill with high expansion cement, concrete cracks when cement expands).
janeskitchen
Original Author
12 years ago
Thanks for the info...we are going to go with a mortar mix as Worthy suggests. Brickeyee, I do not want to take a chance we make a crack where we don't have any!!

Would it be helpful to cover the whole repointed area with something like parging that you do on the exterior, or not? Thanks for your help with this!

fixing crumbling mortar around blocked in basement window

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fixing crumbling mortar around blocked in basement window

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