Wet basements are usually caused by groundwater building up in the soil to a level where hydraulic pressure forces the moisture inside through your foundation’s weakest point. This moisture, if left unchecked, will lead to structural damage, foundation buckling, mold, mildew, the inability to use the basement for storage or living space, and will decrease the value of the entire home. When a home is placed on the market for sale, a moisture-laden basement will either cause a significant reduction in the sale price or the lack of a sale altogether. So whether you are planning on staying in your home for a long time or selling it soon, moisture in the basement must be addressed.
It is always preferable to keep the water out in the first place rather than to collect and pump it back out. Sometimes it is necessary to collect and pump the water out when all reasonable solutions to keep it out fail. Sump pumps are a valuable and indispensable aid during unusually wet events and I encourage their use. But in most situations, they should be just that–a backup system for rare events. By the time the water gets to a sump pump, it has already exerted tremendous hydraulic pressure on your foundation and most likely damaged your walls and floor.
After doing hundreds of site assessments, it has become clear to me that, while each situation is unique, a surprisingly small number of deficiencies occur time and time again. Nearly all of these can be addressed aboveground and should be corrected before more intrusive, disruptive and more expensive below ground solutions—that are still occasionally needed—are sought.
Common causes of and solutions to damp basements
Of course, the gutters need to be properly installed and kept clean and operational, but it doesn’t stop there. Many gutters have small, outdated “residential”-sized downspouts that plug easily and can’t handle the water during a heavy storm. Upgrading to larger “commercial”-sized downspouts is a great improvement and is relatively inexpensive. Downspout extensions protruding at least 5 feet away from the home are also necessary to carry the water away from the foundation. Some commonly used hinges between the downspouts and extensions to ease yard care also leak profusely and should be avoided.
2. Window wells
The function of a window well is to allow for a higher grade for drainage purposes next to the foundation without covering the window. In other words, if not for the well the soil couldn’t be high enough for proper slope away from the foundation. If your basement is wet directly below a window well, the well is probably to blame. The majority of window wells seem to have been improperly installed in the past—it is rare for us to do an inspection of a damp basement without finding a deficient window well.
Several problems are common:
The well is not attached and sealed to the wall, allowing it to pull away and settle, which allows water to easily infiltrate next to the foundation.
The well is simply too short, which allows water to flow over the top and down into the well during a heavy rain event.
The well is made of a sectioned or porous material such as wood or retaining wall blocks, which allows groundwater to enter the well between each of the individual pieces making up the well.
I’ve seen gorgeous hand-made limestone wells that were a real work of art but were the sole cause of ruined drywall and carpet. Remember those landscape designers are NOT waterproofers! Do not let a landscaping firm install hand-made pieced-together wells no matter how much you like the look of the material to be used. Wells need to be properly attached, of a proper height, and of impervious material such as metal, polyurethane, or fiberglass. I am not generally a fan of clear plastic window well covers but in some instances they do help. Their main downfall is longevity—they have a short lifespan and need to be replaced often.
3. Settled backfill
Over time, the soil around your home settles. The end result is that the area adjoining your foundation is lower than the soil level several feet out in your lawn. During heavy rains or rapid snowmelt water pools directly outside of the basement wall and has nowhere to go but down (and into your basement). This settling is to be expected and nearly every home with a basement will have to have this addressed at least once. When the home was new and the foundation was still curing, the backfill couldn’t be compacted without damaging the new wall—it’s simple physics that the soil will eventually settle down to near its original unaltered state. Simply placing additional topsoil next to the foundation cures this extremely common condition. If the area is landscaped, adding more mulch, lava rock, river rock, etc, will NOT help. Those products are for aesthetics and act as a sieve allowing water to flow down through them. The grade must be correct BEFORE those products are added. If you have a home with a warranty, be especially careful about this. Many builders will simply add more mulch or rock disguising and worsening the problem if they get called out on a settled backfill warranty. I have seen many instances where the rock or mulch is over a foot deep next to the house after a warranty claim and the homeowner is baffled as to why their basement is still wet.
Adding more rock or mulch simply won’t work. The landscaping can usually be saved but not without cost so usually, we end up putting that money toward upgrading the landscaping for a more modern look. Don’t forget to inspect under your deck. That area settles just like anywhere else; sometimes it’s even worse if pets have dug holes under the deck. The deck DOES NOT have to come off. We have developed a far less expensive process where we can address settled backfill issues under any deck. After the grade has been corrected, if further measures are needed, the money and effort already expended has never been wasted. I have yet to see a warranty from an underground waterproofing company that doesn’t somehow state that their guarantee is contingent upon the aboveground grade being correct.
4. Landscape edging holding water next to the foundation
If your home has some sort of edging product separating the landscaping from the lawn, make sure that the grade is sufficient to allow stormwater to flow away from the foundation OVER the edging and out into the yard. It is common for edging to be added without adding additional soil next to the foundation and that effectively holds the water in and, once again, it has nowhere to go but down and into your basement. If you add edging, lay a carpenter’s level on top of it going back to the soil (not the top of the mulch or rock) next to the foundation and take corrective measures if the slope is inadequate.
5. Settling of patios, driveways, steps, and sidewalks TOWARDS the foundation
This also is a common situation. It’s a byproduct of settled backfill (#3 above). Sidewalks, steps, driveways, and patios are normally installed when the house is new, and then as the backfill settles, these structures settle along with it. So when a raindrop hits the patio 10 feet out from the house, it simply follows the negative slope back towards the house and seeps into the basement. Mudjacking, where the concrete slurry is injected under a settled concrete structure, can be successful if done on the concrete that was properly reinforced when it was originally constructed, but usually, the settling has cracked and buckled the old concrete to the point that it needs to be torn out and replaced once the grade has been corrected. Many homeowners choose to upgrade to pavers for a more upscale, modern look. Pavers have another benefit: if an area becomes damaged, or if a future utility needs to enter under the patio, sidewalk, or driveway, the pavers in that immediate area are simply pulled up and replaced. This is much easier than dealing with a problem on or under a large slab of concrete.
6. The home sits “too low” in the ground
This is quite common in older homes. Water is flowing back towards the house, but there is no room to add topsoil against the foundation, as the siding is already near the soil line. Often times the front lawn has “raised” over time due to tree roots heaving and raising the soil. Normally the solution here is to construct a swale, berm, or both. A swale is a specialized, aesthetically pleasing shallow, and relatively wide ditch that channels the water out into the lawn away from the basement where it can widen out even further and soak in or dissipate. If properly constructed, a swale blend into the landscape and looks quite natural. A berm is the opposite of a swale—it rises up out of the yard rather than protrudes down into it. Think of it as a small levee or dike that blocks the water from being able to flow towards the foundation. Swales and berms work quite well when we have to use them, but they often have the disadvantage of higher cost due to disrupting
the landscaping next to the foundation and also having to extend out into the lawn which can entail rerouting irrigation lines, removing tree roots, and sodding or seeding when construction is completed. Still, swales and berms are less costly than underground methods and have the added benefit of keeping the water away which is always preferable to move it away. A permit may also be needed if the water is directed to where it may flow into the street.
Anything that restricts, alters, or redirects the flow of surface water around your home has the potential to cause moisture problems in your basement. The old adage, “solving one problem causes another” comes to mind here. Dozens of times each season I encounter homeowners who are heartbroken when their new patio, garage, gazebo, three-season room, etc—something they have painstakingly longed and waited for— causes their basement to become damp or even flood.
Thankfully, we can usually correct the issue, but with a little advance planning the problem—and the costs incurred to solve it– could have been avoided. Remember to take into account what implications any construction project may have on the flow of surface water around your home.
Dealing with a damp basement is never pleasant. At first, it can appear overwhelming. Luckily there are only seven main causes, and by knowing them a homeowner can clarify the underlying cause of their particular situation. Once the cause is known, the solution can soon follow. While pumping water back out of a basement is sometimes required in unusually adverse conditions, it is always preferable to keep the water out in the first place. Addressing potential aboveground deficiencies is the most cost-effective solution and should always be completed before embarking on more expensive underground methods.
© David Pepper 2012