Do-It-Yourself Basement Waterproofing

Easy, DIY Waterproofing Solutions That Will Last

Wet or damp basements are the most frequent complaint of homeowners. Traditional, decades-old basement waterproofing methods have not passed the test of time: "Over 60 per cent of basements have moisture seepage in one form or another, while 38 per cent experience mold and fungus growth due to an elevated moisture level." – The American Society of Home Inspectors. Slab-on-grade buildings suffer similar moisture problems. Now, there is a better solution!

Why basements leak and what to do about it.

Improving Your Home's Health – For over 15 years our RadonSeal® Permanent Concrete Sealer, DIY Crack Injection Kits, and basement waterproofing and radon mitigating products have proven to be the ideal solution for permanently waterproofing wet foundation walls, concrete floors and improving the overall health of your basement and home. Our unique, high-strength, basement waterproofing materials continue to be trusted by professionals and DIY homeowners alike.

How To Make You Wet Basement Dry

The Permanent Concrete Sealer – RadonSeal® is not "your father's" waterproofing paint or sealer. RadonSeal differs from paints and membrane coatings by penetrating deep inside concrete (up to 4"), chemically reacting with lime and alkalis, expanding inside microscopic pores, and curing as a hard mineral. Once cured, RadonSeal will seal your concrete internally against the transmission of water seepage, water vapor and strong enough to seal against harmful radon gas.

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Why Basements Start Leaking Water

A hard driving rainstorm or melting snow can temporarily raises the groundwater level and for every inch of rain, a 1,500 sq. ft. roof sheds almost 1,000 gallons of water. Rain gutters and downspouts get plugged up with debris. New houses have a problem with "reverse grading," which usually occurs several years after construction. Fill dirt around the foundation settles and directs rainwater right to the foundation.

Wet Foundation WallAs the run-off seeps through the soft topsoil around the house, it pushes against the walls and stops at the undisturbed ground just beneath the footings. Footing drains may break as the house settles, or silt up. If the soil is clay, water then starts rising in the disturbed soil around the foundation like inside a pool.

Hydrostatic Pressure – When water accumulates around the foundation, hydrostatic pressure builds up and causes the basement to leak. Clay-rich soils do not drain well and hold rainwater right against the foundation walls. Water pushes its way inside through any cracks or joints and the pores in concrete. Rising groundwater is sometimes the problem or even an underground spring. Houses settle and underground water flows change. New construction down the street may shift groundwater flows and cause basement leaks in your house.

Settling Cracks – As houses settle, concrete develops stress cracks that leak water. Exterior waterproofing disintegrates or separates due to the "alkali attack." When water gets to embedded steel, it rusts, expands and cracks the concrete.

Efflorescence Signifies Water Seepage – Water penetrates into the pores in concrete, dissolves alkalis, and enlarges the pores. As concrete ages, it becomes more and more porous. Initially, the seeping water evaporates, leaving on the surface salts and lime. This "white deposit" or efflorescence is a telltale sign of capillary water seepage.

Plastic Barriers Do Not Last – Concrete slabs, although much thinner than basement walls get even less waterproofing protection. The plastic "vapor barrier" soon disintegrates due to the lime in concrete and over time, the layer of gravel ("drainage pad") silts up. Then, the concrete starts pulling in groundwater by capillary action.

Why Exterior Waterproofing Does Not Last

Tar Foundation SealerTar Waterproofing Is Brittle – Tar waterproofing has absolutely no "give" and cracks as the concrete constantly contracts and expands, and as the house settles. Similarly, tar paper or pargeting (a layer of mortar) on block walls are inelastic and crack.

Concrete is "very strongly alkaline" (pH above 9). Water carries dissolved alkalis to its surface, where they attack any waterproofing coating by saponification ("alkali attack") and even the concrete itself. Alkaline soils in some regions speed up this process and can "eat" away inches of concrete over several years.

All waterproofing coatings gradually break down or separate, even flexible elastomeric liquid membranes. Elastomeric sheet membranes separate as the alkalis attack the primer and taped joints - they are guaranteed for only 5 to 10 years.

In the end, the concrete is on its own! It may continue to do a good job for several years but water will gradually activate alkalis, leach out the concrete, and enlarge the pores, making water seepage inevitable. Water is the root problem – in perfectly dry conditions, concrete and waterproofing would last forever.

Wouldn't it be great to somehow stop water migration by internally sealing the pores and to neutralize the alkalis in concrete surface to protect the concrete and any waterproofing coating against "alkali attack"?

That's exactly what RadonSeal does!

How To Waterproof Your Basement in 4-Steps

Tackling a basement waterproofing project can prove to be daunting task but the labor involved may not be as strenuous as you thought. Follow this basic step-by-step approach for drying out your damp basement:

STEP 1: Remove any paints, sealers, tile adhesive, efflorescence, and oils from the concrete.

STEP 2: Shop-vac the surface of the concrete removing loose or crumbling concrete, mortar, dust, and dirt.

STEP 3: Seal the concrete walls and floor against moisture with RadonSeal®. You can move all your "stuff" to one side of the basement and seal the other side first. Let the concrete dry out for a couple days and then, seal the other side.

STEP 4: Make any repairs to foundation cracks, floor cracks, gaps, control joints, floor-to-wall joints, etc.

How To Seal An Stone Foundation Wall – RadonSeal will strengthen and waterproof old mortar as well as limestone. Remove crumbling mortar then, seal with RadonSeal. Afterwards, tuck point the mortar where needed. RadonSeal will not inhibit the bond of mortar, adhesive, thin set, paints, tiles, etc.

How To Seal A Brick Foundation Wall – RadonSeal is best used on concrete. It can be used to seal brick but you can run the risk of changing the appearance of the brick (leaving a white film on the surface that would be difficult to remove). For waterproofing a brick foundation wall we recommend sealing it with LastiSeal™ Brick & Masonry Sealer.

Customers' feedback and tips on Waterproofing Concrete and Basements

Commercial-Grade, Concrete and Basement Care Products

If your basement is still unfinished and unpainted, our line of waterproofing products will make waterproofing your basement concrete quick, easy and saving you on both time and money.

RadonSeal® Basement Concrete Sealer – Our champion concrete sealer! RadonSeal works deep inside concrete walls, floors, concrete blocks, and cinder blocks both strengthening and waterproofing the substrate permanently. RadonSeal dries clear, leaves no color or film on the surface that can peel off or wear away and cannot be pushed out regardless of hydrostatic water pressure. The cured mineral becomes integral to the concrete. RadonSeal is safe to use indoors because it contains no chemical solvents or VOCs. It's spray-on application is quick and easy for both contractors or homeowners.

The application of RadonSeal is simple. All you will need to apply it with is a hand-pump "garden" sprayer (readily found in major hardware stores). Please take the time to read our RadonSeal Application Instructions & Tips.

DIY Foundation Crack Repair Kits – Our diverse line of foundation crack repairs kits are used for permanently filling cracks in poured concrete walls and stopping leaky cracks. Used by professional waterproofing contractors the low-pressure injection method eliminates any need for drilling making repairs easy enough for homeowners to do themselves. The low viscosity urethane is suitable even for the repair of hairline cracks. The kits arrive to you complete - all you need is a standard caulking gun for injection.

CrackWeld Floor Repair Kits – CrackWeld® provides a quick and permanent repair of stress cracks in basement floors and concrete slabs. CrackWeld's low viscosity, self-leveling resin, can penetrate even inside hairline cracks without the need to rout the crack first! Designed for flooring contractors but also used by homeowners, the kit comes complete with full instruction and a step-by-step video. Cures in minutes and strong (harder than concrete itself).

ElastiPoxy Joint & Crack Filler Kit – ElastiPoxy™ is a unique product for the specific repair of control joints, floor-to-wall joints, cracks in concrete blocks, and wide cracks in concrete, brick, and masonry (>1/2"). When used straight ElastiPoxy offers the desired flexibility, bond, and strength needed to make proper repairs of expansion control and floor-to-wall joints. When mixed with silica sand, it the sealant will provide a rigid repair for waterproofing cracks in concrete blocks walls, wide stress cracks, or for filling concrete spalls in slabs.

How Water Gets Through Concrete

Concrete is naturally porous – typically 10 to 18 percent air (with extremes 2–60%). To make new concrete "workable," a water-to-cement ratio of 0.45–0.50 is the norm but cement only needs a half of the water (0.25 w/c ratio) for hydration. As concrete cures, all the surplus water escapes to its surface and evaporates. This "bleeding water" leaves a network of tiny capillaries (pores) inside the concrete.

We cannot see the pores. Their size ranges from 3 nm (millionths of a mm) to 0.1 mm (the diameter of a human hair). The median is about 1 micron (1,000 nm) but a water molecule is 3,000 times smaller (0.28 nm). By all logic, concrete should leak like a sieve!

So, what holds the water back? Not the concrete but the physics of water itself. Although water not as viscous as molasses, it takes pressure to push it through a dry microscopic pore. Surface tension holds the "blob" of water inside the dry pore until its surface gets wet. But add repeated water pressure during occasional rainstorms or condensation on the interior and after a while, the inside of the pore gets wet and water starts flowing through it.

Concrete is hygroscopic - it attracts water by absorption and once the pores get wet, they draw in water from the ground below by wicking action (capillary suction). Water may take years to start seeping through concrete but nothing holds back gases - invisible water vapor and radon gas flow right through the pores. More on Basement Damp-Proofing

How to Check for Moisture Transmission

DIY concrete moisture testMany home sales get re-negotiated or even canceled when the building inspector discovers moisture in the basement. Make sure to check for leaks and any visible cracks in the concrete, the floor-to-wall joints, expansion control joints in the floor, and all penetrations.

You can test for moisture transmission through the concrete by placing a foot-square of plastic or aluminum foil on the floor or wall, seal the edges with duct tape, and check after a couple of days for drops of water. Alternatively, you can use professional Vapor Transmission Test Kits.

What will building inspectors look for?

  • Dampness – Residual dampness at the base of walls
  • Rust – Signs of rust at the base of steel posts or the heater
  • Rust Stains – Discoloration or decay on wood partitions, paneling, drywall, wood posts
  • Efflorescence – Signs of "white powder" on the concrete walls and floor.
  • Peeling - Peeling floor tiles, paint, or mildewed carpeting
  • Mildew Stains – Stain from mildew on objects stored on the floor
  • Damp Smell – Dampness smell in the carpeting and finishes
  • Musty Odors – A musty smell indicates that molds or mildew have already taken hold
  • Condensation – Windows and concrete
  • Rain Gutters – Plugged or damaged rain gutters
  • Grading – Improper grading, puddling of water, and the growth of moss.

Waterproofing New Concrete Foundations

RadonSeal® preserves new concrete and it protects concrete against the gradual deterioration caused by groundwater. Sealing the concrete early on, particularly before finishing the basement, will help avoid future headaches! If you have a brand new basement, now is the best time to prevent future moisture problems, to waterproof and strengthen the concrete, reduce cracking, efflorescence ("white powder") and dusting, and to preserve the concrete.

As concrete cures, it inevitably develops capillaries. Allow new concrete to cure for at least 28 days and then, deep-seal the poured walls and slab with RadonSeal® Standard. In case of concrete block or cinder block walls, let the mortar cure for at least 14 days and seal them with RadonSeal® Plus.

Waterproofing Foundations on The Exterior

Combining RadonSeal With An Exterior Waterproofing Coating – RadonSeal is usually used in combination with an exterior waterproofing coating, which is required by building codes in most counties. Exterior coating bridges cracks, holes, or defects in the concrete. RadonSeal does the waterproofing job after the coating deteriorates. By neutralizing alkalis in concrete, it also greatly extends the life of the waterproofing coating.

In general, the lower the quality of concrete the higher the need to apply a waterproofing coating over RadonSeal. Unfilled cinder blocks and concrete blocks have only thin walls (1-1/4") on either side of the hollow cores. Some have visible large pores. The most effective RadonSeal application is waterproofing both sides of the walls. But first, the concrete has to cure for 28 days, or 14 days for mortar in block walls. After applying RadonSeal, let the concrete dry out for at least 3 days before applying an exterior waterproofing coating.

However, many contractors have to backfill in just a few days. In that case, use the usual exterior waterproofing coating and later, apply RadonSeal at least on the inside of the walls. Although this will not protect the outer layer of concrete against water, it will still waterproof the walls.

Alternative Waterproofing Methods for Basements

INSTALL A SUMP PUMP ($900–$1,50) – If your water issue is serious (a high water table), you will need to purchase and install a sump pump. Sump pumps drain water from the gravel bed underneath the basement floor. Relying on one sump pump, however, is risky, particularly if your basement is finished! The pump or the grid may fail during a severe storm or spring snow melt. Installing a backup, either a battery-powered backup sump pump or a water-powered backup sump pump is a smart decision and an inexpensive insurance.

INTERIOR DRAINAGE GUTTERS ($3,000–$6,000) – A plastic channel system ("interior gutters") is glued around the perimeter of the basement floor to collect water seeping through the foundation walls and to take it to a sump pump basin. Why is installing plastic channels a bad idea? If you are planning to remodel your basement, common sense would tell you that water should be kept out and not allowed to seep in. It would be impossible to frame and finish the walls because water sitting in the channels behind the drywall would lead to mold and mildew problems. Moreover, the channel system does not address water seeping directly through the concrete floor.

EXTERIOR FOOTING DRAINS ($13,000–$20,000) Excavating the earth next to the foundation walls, laying gravel, installing perimeter drains, removing old tar from foundation walls, sealing the concrete, applying a polymer waterproofing membrane, backfilling, and finally, re-landscaping. Whew!

INTERIOR FRENCH DRAIN ($5,000–$9,000) The "go-to" solution of most waterproofing contractors. To install the French drain, the perimeter of the basement slab must be jackhammered, earth dug out to form a trench, followed by laying a perforated pipe over a stone bed. The pipe will drain the water from underneath the basement floor to a sump basin. The concrete is filled back in. This method does not work very well if the gravel bed is silted up and does little for seepage through basement walls. The French drain method leaves a gap at the floor-to-wall joint to allow water seeping through the walls to flow down to the French drain. These open gaps and the natural vacuum in basements cause the inflow of moisture-laden gas and radon gas from the soil. This leads to increased humidity and harmful radon gas levels in the basement.