Do-It-Yourself Basement Care & Repairs
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Deep-Penetrating Concrete Sealers Do-It-Yourself Basement Care & Repairs |
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Frequently Asked Questions - RadonSealCan I buy your products in a store?No. We ship products directly from the factory to contractors, building owners, and homeowners, which avoids retail mark-ups and sales taxes. Which concrete sealer is best?"I am confused with the different sealers. Which is the best one?" RadonSeal penetrates the deepest (up to 4 inches) into concrete, reacts chemically, bonds and strengthens it. It seals sound concrete against water, vapor and radon gas. It provides the tightest seal and is permanent. The surface does not change, does not bead water, and remains paintable. LastiSeal penetrates very deep (2–4 inches) and hardens inside the concrete or bricks. It is manly designed for waterproofing. Unlike RadonSeal, it does not depend on the content of cement. The surface remains suitable for paints (except latex) and adhesives. Subsurface membrane sealers for concrete are Concrete Armor, Concrete Armor Plus, and Ion-Bond Armor, in order of increased penetration and tight seal. They do not depend on the cement content of the concrete. They provide a water-repellent surface, which beads water on smooth surfaces. Ion-Bond Armor penetrates the deepest and even leaves the surface paintable. For the tightest possible seal, we use a combination of RadonSeal and a membrane sealer. More information on How to select the best sealer for your project Can I seal through paint?"I have recently painted the walls but the basement is still very
damp. Can I still seal it against moisture?" How to remove paints or surface sealersBefore applying a penetrating sealer, all paints, surface sealers, or mastic must be removed first. When fixing a localized seepage through concrete, you could just scrape loose paint and seal the spot but water will soon find another weak area. You can hire a painting contractor or do it yourself. Equipment rental stores offer various options:
Sand blasting cleans concrete most thoroughly both walls and floors but leaves lots of sand everywhere. If there is a good drain, high pressure water-blasting is usually much easier. Floor sanding is only for floors and if the paint is soft, it gums up the sandpaper rendering it ineffective. Shot-blasting is usually the best for cleaning larger floors. Concrete finishing contractors provide this service. Smaller shot-blasters are now also available for the public. Paint strippers require patience and emit fumes. Ideally, the paint should bubble up and lift for easy scraping off. If the stripper dissolves the paint, wipe it off with a rag before it fills the pores in concrete. We use a professional-grade paint and mastic remover - see paint stripper description. How do I remove tile adhesive?Floor tile adhesives (mastic) can be removed with chemical paint strippers or citric acid solvents (delemonene), which do not emit VOC fumes but are effective only on modern water-based adhesives. Mastic removers are sold in stores. We use our Lightning Strip paint & mastic remover, particularly for the old, thick, black mastic. Test it on a small area first. Avoid filling the pores in concrete with diluted mastic. Afterwards, wash the area to remove any residue. Alternatively, you can use a sander or grinder (with a carbide scraper plate). Painted walls and efflorescence?"I wire brushed and acid etched the walls and painted them with a masonry sealer. The basement is mostly dry now but after a short time efflorescence is returning in areas and causing the sealer to peel. I have wire brushed, re-etched, and repainted the problem areas but the efflorescence keeps returning. Can I apply RadonSeal?" How do I remove the white powder (efflorescence)?Water carries dissolved alkalis, lime and minerals from the concrete to the surface, where it evaporates and leaves behind white mineral deposits. Sometimes, it "grows" from the pores like fluffy cotton fibers. If left unchecked, this eventually hollows out and destroys the concrete – it is also called "concrete cancer." Extensive efflorescence prevents proper absorption of RadonSeal and consumes some of it, leaving less for sealing. You can remove light efflorescence with a stainless steel wire brush. Homeowners often use muriatic and other acids (see below) or white vinegar. But if you have extensive efflorescence, you can avoid the hazards of acids and use our acid-free Efflorescence Cleaner. It dissolves and oxidizes efflorescence – makes it disappear. It also eliminates the steps of neutralizing the acid residue and hosing off the surface. More information on cleaning efflorescence. Carbonation: Over time, efflorescence reacts with carbon dioxide in the air and builds up as a rock-like layer of calcium carbonate (limestone). This is very difficult to remove - try a chisel and hammer, sandblasting, or repeated applications of the Efflorescence Cleaner and scrubbing with a stiff brush. Efflorescence in the form of white blotches on a newly poured slab is caused by bleed water carrying lime and alkali to low spots, or by covering the slab with a plastic sheet that does not permit evaporation of water. Difficult to remove – use the same methods as for efflorescence. Laitance: A thin layer of cement particles and free lime that floats to the surface of very wet cement and forms a pale, friable layer when the mixture sets. Caused by high water content in the concrete or by curing under a plastic sheet. If a coating is applied, it can be lifted almost like a carpet. Before coating or sealing, the laitance must be removed by sandblasting, shot-blasting, scarifying, acid etching, or similar. Does RadonSeal cause efflorescence?As RadonSeal cures and expands inside the pores, it purges from the concrete dirt, loose minerals, and old efflorescence for several days. It comes out in a soft, powdery form and can be easily brushed off. This purging is more obvious on older concrete and it confirms that RadonSeal is reacting well. Can I seal a very smooth concrete floor?Power troweling provides a nice-looking, smooth finish on concrete floors. It creates a "hard cap" (crust) on the surface. But when overdone, the surface becomes shiny and the crust may be very thick (1/8" instead of 1/32"), which may lead to problems. (Uncured lumps pushed into the surface while still plastic will become stress points that may cause spider web cracking later. The thick hard cap may spall as the concrete underneath cures and shrinks. Not suitable for painting, adhesives or sealers.) RadonSeal routinely seals machine-troweled concrete like garage floors. But if the surface is "over-beaten," it is difficult to penetrate. You can dampen such surface with water and apply RadonSeal Standard in several light mist applications 10 minutes apart instead of a continuous film. This does not penetrate as deep but still hardens and dust-proofs the surface and at least partially waterproofs the concrete. Unevenly troweled floor: This may happen in some areas when the concrete has higher spots which get hit harder by paddles of the troweling machine. They often become the weak areas for moisture infiltration, as well as condensation, because they trap migrating water similarly to a floor covering and are the cold spots for condensation. Do I have to acid-etch the floor?If the surface looks unusually smooth, you can test its porosity: Or you can check the absorption of RadonSeal by spraying a small 3 x 3 ft. test area. The glistening film should absorb into the concrete within 10 minutes. If not, wipe off the sealer and rinse off (it would protect the concrete against acid etching), and proceed to open up the surface. Acid-etching concrete floorsAlternatives to acid-etching: For best prep, hire a concrete finishing contractor to shot-blast ("bee-bee blast") the floor to a 60 grit finish (CSP Standards, 330 Shot size). Small shot-blasters are now rented out in some areas. Or use a sand-blaster to open up the pores but this leaves lots of sand. Or rent a diamond grinder or a scarifier. Or use a disc or drum floor sander with a very rough sandpaper (16 or 20 grit). Acid etching presents hazards to health and the environment. If overdone, it can "burn" the concrete, eating away cement paste and exposing bare sand. Nonetheless, acid etching is routinely done by homeowners and contractors, and muriatic acid (highly diluted hydrochloric acid) is sold in most hardware stores. But follow carefully the manufacturer's instructions and safety precautions. Always dilute acid in water, not vice versa, and ventilate the area. First, saturate the surface with water to prevent deep penetration of the acid. After carefully adding the acid to water in a plastic bucket, we mix a strong 60/40 or 50/50 solution, pour it on the floor and spread with a stiff bristle broom. In about 10 minutes, it starts bubbling and turning yellow. After 15-20 minutes, the surface should end up with the texture of 60-80 grit sandpaper (buy a sample for comparison). Tight surface in some areas may need repeated spot etching. Do not allow it to dry – as soon as the bubbling stops, neutralize and rinse the surface. It is critical to neutralize all acid residue. Use a 20% ammonia solution or you can use baking soda: Dissolve baking soda (sodium bicarbonate) in a bucket with hot water (1 cup baking soda to 5 gallons of warm water), pour it out on the surface, and spread with a bristle broom. Let it sit for about 20 minutes and hose off or it may leave a white film. Ammonia has a strong odor but does not leave a white film. Thoroughly rinse the surface to get rid of all residues, which would otherwise react with the sealer on the surface. If there is no drain, rinse and wet vac several times. Using the eyedropper test (above), you can check in several locations for consistent absorption of water. Can I seal my finished basement?"My basement is already finished. Can I use RadonSeal to reduce
radon?" "Should I caulk around the bottom of the existing paneled walls?" It would be useless, because radon easily passes through drywall and paneling. Peeling floor tiles?"My floor tiles keep on peeling and the glue has turned into a
white powder." I am busy, can you apply the sealer for me?We have professional applicators available in some areas. Please contact us and advise your location. However, our products are designed for an easy do-it-yourself installation. Get a relative to do it or hire a handyman. I meet the 4 pCi/L limit, isn't that enough?The 4 pCi/L level is not a "safe" level. Radon gas is dangerous
at any level. If this is a home for your family, you should always try to
reduce radon to a minimum, particularly if you have children. Why doesn't EPA recommend sealers?EPA (1990): "Sealing cracks and other openings in the foundation
is a basic part of most approaches to radon reduction. EPA does not recommend
the use of sealing alone to reduce radon because, by itself, sealing has
not been shown to lower radon levels significantly or consistently." RadonSeal penetrating concrete sealer was not available in 1990. It is not a surface sealer but penetrates up to 4 inches inside concrete and seals it internally by a chemical reaction. If there are any openings or cracks, they also have to be caulked just like with all radon mitigation methods. What if I already have a radon fan system?The fan cannot "suck out" all the radon gas from underneath the slab and none from outside the walls. But soil is not perfectly permeable to radon gas and over time, the gravel under the slab tends to silt up. RadonSeal will reduce your radon level further by sealing both the slab and the walls. It will also lower the operating costs of the fan-based system ($150/year on average) by reducing the energy losses in heated/cooled air now pulled in a reverse direction through the slab. And moreover, it will act as a backup during equipment or power failures. Using both methods simultaneously is the safest approach. The more RadonSeal I apply, the better?No. Over-spraying should be normally avoided. For the tightest possible seal, particularly against water vapor coming through concrete floors, you can apply additional light applications as long as the concrete absorbs the sealer. If you over-apply or let the sealer run and puddle, it will seal the pores in the concrete's surface and give it a hard, glassy or whitish finish. Such surface is unpaintable, unless sanded first. What if I have some RadonSeal left?It has a long shelf life – two years. Seal your garage floor. It will purge oils and dirt from inside the concrete within several days, waterproof it against wicking water, and make spills easy to wash off. Or apply it to your concrete steps, sidewalks, or driveway for protection against spalling or pitting due to salts and "freeze-thaw" damage. How to repair cracks and gapsFix cracks only after applying RadonSeal because they help the sealer penetrate into the concrete. Moreover, RadonSeal tends to close most hairline cracks in slabs as it expands inside the concrete. And RadonSeal strengthens the concrete and eliminates or reduces further cracking. The usual repairs with a caulk or hydraulic cement do not last. Caulk peels and hydraulic cement, which does not adhere well to concrete and is very rigid, gets loose and allows water to seep around it. Repair hairline or wide cracks in poured concrete walls permanently with our concrete crack injection kits. Forceful expansion of the injected polyurethane polymer ensures that the entire depth of the crack is filled, so that water will never find the crack again. Cracks in block walls are more difficult to repair – use our Epoxy Crack Filler for a strong and permanent repair. For various options on repairing cracks in concrete floor slabs and floor-to-wall joints, visit How to Repair Cracks in Concrete Slabs and Corners Caulk around all penetrations through the floor or walls. To stop or prevent leaks around pipes, use our crack injection kits which will fill the full depth of the wall and bond to the piping. If water leaks develops around tie rods, chisel out some concrete and stuff it with our Epoxy Crack Filler. Any questions? Please contact us by e-mail, MADE IN USA |
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