How to Repair a Wet Basement

The wet basement curse

Most homes develop basement leaks within 10 to 15 years. Over 60 percent of homes have a leaking basement. You are not alone - wet basements are the most frequent complaint of homeowners.

Fixing cracks is relatively straightforward but once water starts seeping through the concrete, the homeowner faces $1,000's in repair bills. If you have a damp basement, musty odors, efflorescence ("white powder"), or minor water leaks, fix it now before it gets worse and much more expensive.

How to make a wet basement dry

RadonSeal Penetrating Concrete Sealer waterproofs leaky basements. It penetrates deep into concrete (up to 4"), reacts with alkali, expands into pores, and hardens as a mineral. This seals the concrete against water leaks and dampness.

RadonSeal works inside the concrete. Unlike waterproofing surface sealers, it cannot get lifted by efflorescence or water pressure. And it cannot peel or wear off - once the concrete sealed, the seal is permanent!

RadonSeal is non-toxic, nonflammable, and does not contain chemical solvents or release VOCs. Its spray-on application is quick and easy for contractors or homeowners.

RadonSeal seals bare (unpainted) cementitious materials:

• Poured concrete
• Concrete blocks or cinder blocks
• Mortar in block walls or stone foundations.

Always seal the whole basement - both the floor and walls. If you seal only the leaking area, water will find another way.

Leaking poured concrete

Concrete usually starts leaking only intermittently after heavy rains. Before sealing with RadonSeal, let the concrete dry out to minimize dilution of the sealer in the water inside concrete. First, wipe off or wet vac water from the surface.

RadonSeal stops even active leaks under hydrostatic pressure through sound concrete. It displaces water inside the pores and hardens, gradually throttling off the seepage. But the leaky area will require repeated applications. Let it partially cure for a day and then apply additional applications, provided the concrete still absorbs it.

Try to make the area as dry as possible. If the area remains continuously moist, RadonSeal cannot fully cure and harden. Ventilate the area and install a fan or dehumidifier for several days before and after the application.

Leaking concrete blocks or cinder blocks

Blocks are very porous and only 1-1/4 inches separates the core from the water outside. That's why 90 percent of basements with block walls leak within 15 years. It is best to fill the cores with concrete during construction.

If the seepage is intermittent, wait until it dries out before spraying on RadonSeal Plus, in order to minimize dilution of the sealer inside concrete. Ventilate the area or install a fan. After the first 2 applications of RadonSeal Plus, let it dry out and partially cure for a day or more to avoid pushing the penetrating sealer into the cores. Then, apply 2 (3) more applications of RadonSeal. Cinder blocks are particularly porous and typically need an extra application of RadonSeal Plus.

Wet blocks are hard to seal. There is only a thin wall to seal and unfilled hollow cores hold a column of water, which pushes it out under pressure. Drain the water first - drill 1/4 or 3/8-inch holes in the bottom blocks and let dry out for a couple of days. Ventilate the area to evaporate water held in the pores of the blocks and then, to help RadonSeal cure. Afterwards, caulk the drain holes.

Leached out concrete or lightweight blocks

RadonSeal reacts chemically inside concrete with alkalis and "free lime" (calcium hydroxide) produced during the hydration of cement paste. But water gradually leaches out the free lime from concrete subjected to continuous seepage. Lightweight CMU's (Concrete Masonry Units), hadite blocks, and decorative splitface blocks are made with little or no cement, leaving little for RadonSeal to react with. The pores in concrete have to be first filled with a substitute.

Thoroughly mix baking soda (3 tablespoons per gallon) in a bucket of hot water. Mix and let settle for a couple of hours. Leaving the sediment behind, pour the solution into a pump garden sprayer and spray it on the concrete. Do not flood, it should all seep into the concrete.

For large projects, purchase calcium hydroxide (hydrated lime) from a local chemical company (below $20 for a 50-lb bag). Mix one cup per 5-gallon bucket, let settle for 24 hours, and spray on with a power washer.

Let dry. If there is residue left on the surface, wash it off with water and a mop or brush. Apply RadonSeal Plus per the application instructions.

Popcorn blocks

These are blocks made of a very course aggregate that have straw-size holes. They can hardly slow down water or gases.

First, spray on 2 applications of RadonSeal Plus. After it dries, trowel on a layer of Mapei "Keraset Professional Grade Dry-Set Mortar." It is easy to apply and will not shrink. It contains special resins, which make it unsuitable for RadonSeal. Instead, use our Ion-Bond Armor membrane sealer, which creates a subsurface water-repellent membrane that resists negative side water pressure.

Leaky stone foundations walls

The problem usually is water leaking through the mortar. First scrape out and brush off with a stainless steel brush (no rusty specs) any loose or soft mortar. Then, apply RadonSeal Plus. It will leave a whitish film on the stones. If the wall is decorative, apply RadonSeal only on the mortar with a brush or sponge and wipe off the stones with a wet rag within about 10 minutes.

Let dry out and cure for at least 3 days before re-pointing (tuck-pointing). In addition to sealing the old mortar, RadonSeal will improve the adhesion of the new mortar and by neutralizing alkali, protect it against "cold joint" separation.

RadonSeal also seals porous limestone by reacting with lime. If you have another type of porous stone that you would like to seal, just consult us by e-mail or telephone.

Fixing cracks or gaps

Before fixing cracks, seal the concrete with RadonSeal. Any cracks help its penetration into the concrete.

RadonSeal is not a caulk and does not seal cracks or defects in concrete. But when it cures and expands inside the concrete, it tends to close off hairline cracks (thinner than a credit card).

For larger cracks, you can hire a local waterproofing contractor to repair them by injection.

Or you can fill cracks in slabs with self-leveling polyurethane caulk, which is very "runny." It deep-fills the gap and resists water pressure, is durable and remains elastic as the concrete moves. If the crack is wet, use a marine caulk and adhesive. And if the crack is very wide, use hydraulic cement but it lacks flexibility and gets loose after a couple of years.

Before caulking, you have to open up the cracks. Instead of the classic hammer and chisel" technique, rent a right-angle grinder with a 4-inch wheel for concrete or use a circular saw with a blade for concrete, going about 1/2" deep. For hydraulic cement, the sides should be inverted V-shape.

Other waterproofing measures

Water can do much worse than seep into the basement - water pressure can cause structural damage and buckle basement walls. Keep water away from the foundation! Make sure that there is good drainage - footing drains, gravel under the slab, a layer of gravel or drainage mats on the walls to quickly take rainwater down to the footing drains, and drains from window wells to footing drains.

The traditional approach is trying different remedies, proceeding from the simpler to the elaborate and expensive. The following summarizes the usual waterproofing methods, proceeding from the basic, common sense steps:

Rain gutters:

Maintain the gutters each spring to repair damage from snow loads and each fall to clean out leaves and debris. Add extensions to downspouts to take roof run-off water 10 ft. (min. 4 ft.) away from the foundation. Install splash blocks.

Grading:

The soil should slope away from the house on all sides of the foundation one inch per foot for 10 ft. (min. 4 ft.). You may need a truckload of soil. Old concrete walkways, driveways or patios that slope toward the foundation should be replaced.

Grass:

Remove flower beds, vegetable gardens, bushes and trees from around the foundations and seed the area with grass.

Driveway:

Patch cracks in the driveway using cold-mix asphalt patching compound.

Cracks:

Deep-fill all cracks and gaps with self-leveling polyurethane caulk, which remains flexible and resists pressure. If the crack is wet or larger than 1/4", use hydraulic cement. Or your local waterproofing professional can fix structural cracks by injecting epoxy.

Condensation:

Excessive humidity from seeping water vapor condenses on cold surfaces. Put insulation on cold water tanks, water piping, and cold air ducts. Damp proof your basement with RadonSeal.

Dehumidifiers:

One or two good-capacity dehumidifiers will reduce humidity. But the initial and operating costs are high. They also pull in more moisture from the ground, which accelerates the deterioration of the concrete.

Window wells:

If they drain poorly, install window well covers. Or dig out and drain to footing drains.

Underground drainage systems:

Call a drain-and-sewer-cleaning contractor who will use a long power snake to try to clear the lines. But often they just have to be capped off at the surface and abandoned.

Curtain drains:

Excavate a trench alongside the house and fill it with gravel to stop surface water from getting to the foundation. French drain with a perforated PVC pipe in the gravel takes surface water away from the house.

Dry wells for rainwater:

Install a 3 ft. deep hole filled with gravel and wrapped with landscape fabric against silt at least 10 ft. from the house, or a tank that allows run-off to soak into the ground. An underground 4-in. PVC pipe brings the run-off from downspouts. Each well can usually handle runoff from a 500 sq.ft. section of roof.

Sump pump:

Sump pumps relieve excessive water pressure. Creating a sump and installing a sump pump costs $300 to $600. Install an airtight cover to prevent the release of vapor and radon. Complete reliance on a pump is unwise. Many sump pumps cannot handle large volumes of water in severe storms, may burn out, be swamped, or the power may go off.

Interior gutters:

A plastic channel system collects water seeping through the basement walls and routes it to a floor drain or sump pump. It works after the water has entered and does not address dampness or seepage through the floor. Usual cost $3,000 to $5,000.

Interior footing drains:

May be needed when footing drains break or silt up. Perimeter drain system made of 4-in. perforated PVC pipe laid in gravel under the floor inside foundation footings, which carries water to a sump pump before it enters. Do not leave a gap next to the walls - it would let in vapor and radon. It requires extensive jack hammering and usually costs $3,000 to $8,000.

Exterior footing drains:

Installation requires removing landscaping, excavating to expose the foundation down to the footings, waterproofing the walls, and laying perimeter footing drains in a bed of gravel. Add fiberglass fabric or polyethylene sheets on the coating for water barrier, because asphalt coating on concrete cracks and deteriorates. The cost is $5,000 to $10,000, or more.

RadonSeal waterproofs and damp proofs concrete and will save you $1,000's on basement repairs. By bonding and strengthening concrete, and encapsulating embedded steel, it also eliminates or reduces cracking and preserves the concrete.

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Radon Mitigation & Waterproofing Concrete Sealer Co.
Novion Inc., 18 L'Hermitage Drive, Shelton, CT 06484 USA
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