VCR Ate My Copy of The Half-Assed Approach to Foundation Repair
February 9, 2014 5:00 PM   Subscribe

The decades-old parging/plaster on our basement walls is scabby and peeling. The concrete itself is crumbly in places and there are a couple of cracks. It seems to me that the solution to my problem is to remove the old parging/plaster, fill the cracks with hydraulic cement, and patch the crumbly parts. But I'm less clear on the hows, whys, and whens.

I guess my options for removing the old parging/plaster are using a solvent to dissolve it or a wire brush. Not a fan of the solvent, due to ventilation issues and our cats, so I'm leaning towards cordoning sections of the wall with poly sheeting to keep dust from getting everywhere, putting on a respirator, and scouring it.

Question 1: Is there a good time of the year to do that, or optimal conditions, temperature/humidity-wise? It's currently 15C in the basement, and around -20C outside. Will that make the cement more fragile if subjected to scrubbing, or make the crumbly parts crumblier?

Question 2: In a similar vein, what are the optimal conditions for applying hydraulic cement to cracks? Cold/dry, or hot/humid?

Question 3: Cleaning/clearing out the crumbly areas and patching. Would hydraulic cement also be the thing to use here? Does it require driving some spikes into the wall to give the patch material something to hold onto, or do you use some sort of lath, which would presumably also need to be anchored?

Question 4: What do we do after that's all done? Due to the smaller space and layout, it's not likely we'd be able to put any sort of code-approved bedroom down there, but it would be nice to not have it looking like a dungeon. Should a new coat of parging or sealant be applied to the walls, or a membrane so moisture doesn't get trapped in the concrete (Presumably the cause of the crumbliness), or a product like DRIcore's wall application?

Miscellaneous Basement Facts, Many of Which Are Probably Negligible, But If I Knew What Was Relevant And What Wasn't I Probably Wouldn't Be Asking My Question In The First Place:

- House is 100 years old
- 3/4 style basement with a crawl space
- Walls are poured concrete, about 7' high
- It looks as though the house originally rested on the ground, or was much closer to it, and at some point was jacked up and the 2' to 3' that's above ground was added to it
- Frost line here is considered 6' minimum, soil composition mostly clay I think
- Despite the below ground part of the walls only being 4' to 5' high, the 2' depth of the sump hole leads me to assume that the footers/floor are a similar depth/thickness, which gives a total depth of approximately 7'
- No evidence of shifting
- Sump hole only has one outlet, presumably it drains to the storm sewer
- No backflow valve
- No weeping tile/french drain
- Cracks in basement wall correspond to a downspout on the exterior wall that drained right beside the house; when we moved in I attached another length of downspout to direct water away, and there hasn't been any water since
- Presumably no membrane on exterior of basement walls, any coating that's been applied is probably long gone
- We run a dehumidifier in the summer
posted by Alvy Ampersand to Home & Garden (6 answers total) 2 users marked this as a favorite
We have a 90 year-old house, with a full-height cellar. It used to be hell-hole scary, and is now gleaming and white and shiny. Cracks were cleaned up, chipped-out to solid, and then the voids were filled with Actual Portland Cement (of which kind I cannot say, but your local masonry supply store can help). I should note that this was all interior work. Walls, once having had a right going-over with a wire brush to remove any last gasps of paint or dust, were washed with a dilute bleach mix. After that, we coated them with Tamoseal, which is a wonderous hydraulic cement / polymer stuff that you mix up and slap on with a big walrus-moustache brush. You can do the Tamoseal the same day as the repair work.

I'm guessing you already live there? Do you already have a Basement With Things In It? No worries. You can do a whole wall in a fun, team-building day (especially if you figure there will also be a nice hamburger for lunch) so that with a month of weekend work, you're all set.

I'll answer your questions about painting the rafters later, when you ask them.

Ooh, "parging." Thank you for the new word!
posted by mimi at 5:30 PM on February 9, 2014 [1 favorite]

My brother is a concrete and building contractor and the only answer here is to get a professional. You have too many variables. The only question I can answer is probably don't do it in the winter. Water freezing and then draining. Water goes where it wants to and it's best looked at during warm weather to avoid freezing situations in winter. At least get someone to look at it and give you some idea of what you're looking at.
posted by Marie Mon Dieu at 5:46 PM on February 9, 2014 [1 favorite]

Possibly, a thing to do afterwards: insulate the concrete from the inside and put some gypsum over it.
posted by Monday, stony Monday at 6:10 PM on February 9, 2014 [1 favorite]

Thanks, everyone!
posted by Alvy Ampersand at 7:36 AM on February 11, 2014

Here's a before-and-after photo for incentive!
posted by mimi at 3:21 PM on February 11, 2014

Holy cow, that's quite a crack!

Heh, regarding rafters/joists, I was probably just going to scrape them as they're also covered in a scabby whitewash.
posted by Alvy Ampersand at 9:00 AM on February 13, 2014

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