Pouring a concrete slab in old basement


Old 11-24-14, 10:34 AM
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Pouring a concrete slab in old basement

I'm looking for some advice on a project I'd like to undertake in the spring/early summer this coming year. I bought an 1860's farm house, post and beam on a field stone foundation. The main section of the house has a full basement, and the later addition has a crawl space. The full basement currently has a few inches of crushed gravel on top of clay(fitting as I live on Clay st.) It is moist down there. This winter I am re-pointing the foundation and then painting it with drylock or comparable sealing paint. My goal after that is to have a concrete floor poured in. I'm planning on 4" of cement, but I'm not sure if I should remove the gravel, and pack the ground, and how I should build in a drainage system. I would think I would want some type of collecting troth around the perimeter to a sump-pump, but I don't know what products are out there, or if this would be the proper thing to do. Any advice for this project would be great! Also, this sub-forum is the only place that seemed appropriate to place this question, if it should be moved else where please do.
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Old 11-24-14, 11:10 AM
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First, waterproofing is best done outside by keeping the water away from the foundation in the first place with gutters, grading and downspout extensions. If that's not enough, then an interior mitigation system like you propose would be warranted. Given that you do not have a slab poured yet, I would also look at putting a vapor barrier beneath it when you do.
Old 11-24-14, 11:20 AM
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I just put on a new roof, and with that made sure to redirect all water away from the foundation wall, and for the most part, the grading is in my favor. Thank you for the suggestion of a vapor barrier. Do you recommend any products in specific, and should I remove the crushed gravel?

Edit: I would consider just compacting the gravel, but I'm concerned about headroom. I can stand up easily right now without feeling like I need to duck, with and additional 4" It might seem tight.

Last edited by jbels; 11-24-14 at 01:24 PM. Reason: More info.
Old 11-24-14, 06:26 PM
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15mm stego's most commonly spec'd from the jobs i see - 6mil plastic still works IF you can deep the conc jabonies from making a mess out of it,,, 4" is fine & even 3" is ok,,, don't expect drylock to work successfully - my $.02 is let the interior stone stay uncoated & let it breathe as is best for stone bsmt walls,,, do you have a foundation or just bsmt walls ? don't laugh - that wasn't uncommon & we've work'd on several laid-up stone walls supporting houses w/NO foundations the houses're still plumb

since its not unforeseen you'll have some future wall leaks, it might be a good idea to place 3" s&d about the perimeter holes down terminating in a sump,,, this is the best place i've found to buy - Zoeller 31 0444 Sump Basin Height 22 in 22 Gal | eBay - same for pumps - zoeller m-53 is the wtrproofing trade standard - cover from fergusom plumbing supply in your town

i wouldn't use either welded-wire mesh OR FIBER - a properly installed jnt pattern will be more than sufficient

good luck !

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