Basement waterproofing

Old 04-20-15, 10:35 AM
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Basement waterproofing

I will be moving into a house this year with an unfinished basement. The basement has never leaked or flooded despite being exposed to lots of rain and snow over its 20-year life. I'm not aware that it has any built-in waterproofing mechanics, but I think it does have a sump pump. In addition, there is a dehumidifier that's always running. It's attached to its own outflow so it can get rid of the moisture it collects.

I'm going to be converting the basement into a living area, and in one corner, a home recording studio. I want to be absolutely sure it will always stay dry. Given the conditions I've mentioned, would it be sufficient to apply a waterproofing agent to the floors and walls on my own?

I'm not totally new to DIY home improvement, but this specific topic is a first for me. If I haven't provided enough info, let me know! I'd appreciate any advice on this topic. Having a pro do it is an option, and it's in the budget, but I like doing things myself when I feel I can do them well and safely.
Old 04-20-15, 11:30 AM
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Welcome to the forums!

It's not uncommon for a basement to need a dehumidifier. Is there any visual signs of moisture in the foundation walls or slab? A cheap effective way to test the concrete is to tape a few square feet of plastic to the slab and then come back in a few days to see if moisture collected under the plastic [a garbage bag works fine]

I'm sure you know that waterproofing is achieved on the exterior side of the foundation. Anything done on the interior side is just managing the water that gets thru. While coatings like drylok help a little they shouldn't be relied on to be the soles means of keeping the inside dry.
Old 04-20-15, 02:20 PM
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Correction on marksr's comment.

Very often, some foundations (block or poured concrete) placed of the common narrow strip footings and the slab poured later, resting on the inside edge of the footings need interior drain tile (new or existing construction) need interior drain tile since water can easily go under the wall foundation and exert upward pressure within the outer footprint of the home. This pressure can make the water leak through the joint between the wall and slab or through cracks in the slab caused by shrinkage, joints or the upward soil/water pressure.

I know of several builders that automatically install both interior and exterior systems on all home to enhance their reputation and reduce call-backs that lead to more call backs for other parts of the homes.

Very, very common here because of the very high percentage of the homes having finished basements or walk-outs because we have 4' frost depth that are well suited for split levels and walk-outs or regular basements.


Last edited by Concretemasonry; 04-20-15 at 05:13 PM.
Old 04-20-15, 04:04 PM
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Unless this house has been in your family or owned by a close friend for 20 years, and you know for yourself it has always been dry, I wouldn't take the word of someone else. If you are 100% positive there has never been any leaks in the basement, I would leave well enough alone and begin the finishing process.

Adding a waterproofing agent to the inside is not going to offer any significant flood protection in my opinion. Just make sure the walls are constructed properly to control moisture and air flow to prevent mold growth.
Old 04-21-15, 06:00 AM
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These are all very helpful replies. Thanks!

The home has been owned by family its entire existence (it was designed by a family member). In fact, I should ask her if she knows whether the contractors built in basement waterproofing measures.
Old 04-21-15, 06:38 AM
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Hi audiodef and welcome to the forum,
I know this isn't what you want to hear, but your basement is not dry and was never waterproofed. The extreme measures that would stop all water are rare and would never have been cost effective back when this house was built.

It gets worse. Liquid water is only half the problem as moisture vapor passes right through a foundation and if blocked at any point, like a vapor barrier on the inside, it will accumulate until that point is equally as wet as the outside.

And more, as summer humidity presents a condensation potential if humid air (you do have some in MD?) finds its way through whatever you build for walls and reaches the cool concrete.

And even more. It is a basement built like a bathtub and a leaky water pipe or sink that overflows can send a flood down there with inconvenient results. A sump pump and planned drainage are essential in ANY basement.

The purpose in this rant is to make sure you don't get convinced your basement is dry and move forward with good intentions and end up growing things no one wants in their house. I'll attach a link to a building science corp article to get you started, but follow their links as basements have been discussed here and there with information that can make your project a success.

Have to ask, is your handle generic or are you one of us in the hearing impaired world?

BSD-103: Understanding Basements — Building Science Information


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