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Waterproofing Foundations

By Tim Carter
©1993-2008 Tim Carter
Summary: Damproofing and waterproofing should not be confused. Damproofing, a liquid asphalt, does not provide foundation waterproofing. Hot asphalt and rubber coating and an insulating panel will fully protect your foundation.

You really can't be too careful when you start to build a new home. There are so many time-delay booby traps that can spring on you months or years after you move in. One that tends to shock many people is the simple task of waterproofing a foundation system. I can hear you now, "Tim, my builder did waterproof my foundation." Well, believe it or not in many cases that is not true.

Yes, your builder has already or plans to spray a black liquid on your foundation. He may even call it waterproofing. But the fact is this product may be just damproofing. There is a significant difference between damproofing and waterproofing. Because the buzzword mold is now as loud as the steel-against-steel clash of wheels on the rails of the L, you need to make sure the moisture from the soil can't possibly invade your new basement walls.

Perhaps the best way to start is to go back in time to a basement in an old home. Surely you can recall that smell, that dank moldy smell of an old basement. You were smelling mold and its growth was fueled by the constant stream of moisture from the soil through both the unprotected walls and through the concrete slab you walked across. Years ago builders didn't regularly apply even a simple tar coating to foundations. They did not have access to large sheets of plastic that help retard the transfer of water vapor from soil through concrete slabs.

And believe me, water vapor readily passes through concrete. Granted, it does not transfer at the same rate as perhaps paper or cloth, but it does move to an environment of lower vapor pressure. Liquid water can soak into concrete. Surely you have seen damp patches of concrete before. Proof of this is easy as efflorescence is a prime example of water movement. The water enters the concrete, dissolves salts and then moves towards your basement. Once at the surface of the concrete wall, the liquid water evaporates and leaves the salt deposits behind.


Prevent a wet basements by using this Basement Waterproofing Checklist to hire a great professional. I offer a 100% Money Back Guarantee.

To permanently stop water and water vapor from entering your foundation walls, you need to waterproof them. There are any number of systems that do this, but I prefer the spray-on systems that seal the pores of the concrete. But don't confuse waterproofing with damproofing, not for a moment.

Damproofing is an inexpensive way to meet the lowest minimum standard of the building code. The usual weapon of choice for damprooofing is simple hot liquid asphalt sprayed on the concrete. Liquid asphalt is an excellent damproofing material, but alone it is not a waterproofing system.

And while we are speaking of the code, here is one of the traps. Every local building code can be different, but most state that unfinished basement living spaces just have to be damproofed. But what happens if you know you are going to finish your basement a year or so after you move in? The answer is to waterproof the foundation now for that possibility and to ensure your basement will indeed stay dry even if it remains unfinished.

The waterproofing method I used on my own home is still available. It is a mixture of hot asphalt and rubber. The coating ends up being about one eighth inch thick or even thicker. A special insulating panel is placed in the hot liquid that helps protect the coating from damage during backfilling and it acts as both an insulator and a drainage plane. The rubber in the mixture imparts elasticity to the coating so if the foundation cracks, the coating stretches over the crack to provide protection.

Damproofing compounds can't do this. If the foundation wall cracks, and most develop tiny shrinkage cracks over time, water can readily pass through to your basement. It is also better to waterproof from the outside rather than try to stop water once it is already into your basement space. Spend the money now and waterproof before the builder backfills.

 






Comments

Camie Crawford
27 Nov 2007, 20:31
Hello,

My garage is similar to a basement in that two sides of it are nestled within a hillside. It was originally built in 1950. There's efflorescence and some hairline cracks and surface corrosion. Being that I can't waterproof the outside (the side nestled in the hill) is it recommended that I coat the inside of the garage walls with waterproofer? Or would this risk routing the water that would otherwise seep through the garage, now to another area of the house on that same level?

Thanks!
Camie
ATB
28 Nov 2007, 07:38
Camie,
Please go to the Drainage category of AsktheBuilder.com and read just about every article, *especially* the ones dealing with Linear French Drains. That is all you need-a linear french drain up on the hill.
Richard Wobbe
09 Jan 2008, 10:27
I was having leakage from a concrete basement wall that is 5 feet underground(house is 25 years old). Thanks to you I know the difference between dampprofing and waterproofing (I have neither). I received a bid of $12,000 for a french drain (120 linear foot around foundation). I am retired and dug a hole 2 feet deep and 3 feet on both sides of the leakage and 2 feet from the foundation. I then covered the hole with 2 layers of heavy plastic. This stopped the leakage and was real cheap.
Should I be concerned that this is just a quick fix that might cause other problems in the future.
Dick Wobbe, St. Louis, Mo
314-892-7753
AsktheBuilder
09 Jan 2008, 10:34
Richard,
For a permanent solution, install one of my Linear French Drains. Go to my Drainage category.
Mike
02 Feb 2008, 16:50
We built our house five years ago and within two years the concrete foundation developed two vertical cracks. Each runs top to bottom and match exactly with either side of the steps leading to the front door. The foundation for the steps is also concrete and is attached to the foundation (poured at the same time). The foundation was dampproofed with liquid asphalt when we built to house. The cracks are generally 1/16" wide and have not widened over the last three years. Water does come through the cracks when it rains hard for prolonmged periods of time. I recently decided to finish my basement. I plan to fill the cracks with a liquid cement and then cover the walls with a product to seal the interior walls of the basement with a waterproofing paint. I am wondering if the water will create further structural damage to the foundation over time since it will no longer be able to leak through. I am also wondering how concerned I should be about the fact that the foundation cracked at the points where the foundation and steps meet.

Thanks,

Mike.
AsktheBuilder
02 Feb 2008, 17:51
Mike,
You need to monitor the cracks. Make a mark across them and measure accurately. If the width grows by 50%, call in a structural engineer.
Sandra
15 Feb 2008, 21:53
We recently bought a house that was built in 1923, making the house 85 years old so there probably wasn't much in the way done to waterproof the foundation. We've recently noticed some water damage to the stairs leading up to the partial basement. The water seems to be coming from the concrete walls & there's some white chalky substance leaching out of the walls. What can I do to protect the basement from further deterioration?
AsktheBuilder
16 Feb 2008, 10:25
Sandra,
Simple. Read all of my Drainage category columns and install a Linear French Drain to stop the water infiltration.
Sandra
16 Feb 2008, 12:11
Thanks for your email. I don't think that we can install a linear french drain anymore since we put in a concrete patio that covers the entire backyard. What do you recommend for this type of situation?
Tammy
22 Apr 2008, 13:39
I bought a house last year that was built in 1986. I discovered a fireplace add-on on the outside of the house that was holding water and so I put a pump in it to drain it. I discovered tiny cracks in the block of the house which water continued to pour out of and fill the add-on back up. There is no water coming into the house at this point and the home warranty company will not cover any repairs. I think that there may be an underground stream or drainage issue as the driveway apron has separated from the garage and there is a deep void under it. I suspect that the two problems may be related. I would like to get someone to pump gravel back under the garage apron (but I'm not sure who) and to rip out the fireplace add-on and waterproof and backfill that area. I am concerned that this will divert water into my house (which has a sump pump). Any suggestions on who to call or what to do?

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