Before finishing a basement, is it recommended to seal the walls and floors? Block walls with solid floor and 2 inch drainage gap between wall and floor. Basement is dry and never had a problem with water and all walls underground. Getting feedback from family and friends in both directions. Professional guidance would be greatly appreciated.
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Since the walls are dry and have always been dry it wouldn't hurt to seal them. Probably won't help much either.
Drain gap is good espically if connected to a sump pump.
Ideally, the basement should have had a drainage system around the perimeter and been sealed on the outside before it was backfilled.
Whether or not that was done, adding sealing on the inside can't hurt. There are several paint-like sealing products available and doing it now sure beats trying to do it after the basement has been finished. Think of it as insurance.
Did you ever check for radon? I bought some spray on sealer for my basement a while back, try googling radon seal. You might need it. Also seals out moisture vapor. After you spray, put a self-leveling polyurethane caulk in the crack where the wall meets the floor.
Typically, basement walls and floors are sealed on the outside, not the inside because the ground in which the basement is buried contains high levels of moisture under even normal 'dry' conditions (and can contain large amounts of liquid water under wet conditions). For this reason, the waterproofing for basements runs counter to the practise for applying VB to framed walls above grade, where the VB is applied to the interior of the walls to prevent human-generated moisture (baths, cooking, etc.) from penetrating the wall cavity.
In older places, felt was laid under the slab and bituminous sealer was rolled or sprayed on the outside of the walls. In newer construction, poly sheeting VB is laid on the gravel bed before the slab is poured and membranes such as 'Blueskin' are applied to the exterior of the walls, especially if block is used.
Ideally, you should apply membrane or liquid sealant to the exterior, but if you can't do that, use rigid foam board insulation and tape the joints with glasclad tape to get a double bang for your buck. Under no circumstances seal the floor so tightly that any water which does get in (through walls, for instance) cannot drain back out again.
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Something to consider since you have block walls- If you seal the block, and water gets past any exterior waterproofing, it could get trapped in the cores of the block.
But since you said there's never been any problem with water in the basement, I'd probably go ahead and seal it.
I don't think there is need to seal. As an example, I'm doing my basement this way: I am using 3/4" foam panels against unsealed block foundation wall. Am using blue kind from Lowes with thin plastic sheets adhered to both sides. Then predrill and pre-bevel(forgot the word for drilling out conical place for bugle-heads of the screws) 1x3 furring strips and attach directly over the foam panels into foundation using tapcon screws. I am not overly concerned about the plumb or the straightness of the wall. I will be using paperless sheetrock to finish, outlets that are exposed with metal wire-mold and vinyl base molding. The top of foundation is also covered with foam and all joints are sealed with foam from the can.
I think this will control whatever moisture will carry in and also provide some insulation. Most of my basement is under ground so it is somewhat stable. I made my own kind of french drain around the perimeter but that is another story. I think this way, you have mechanical seal as well as some insulation. Hope this helps.
countersink