While Flex Seal can temporarily seal small, non-structural concrete cracks on the surface, it is not a permanent or reliable solution for concrete foundations.
Flex Seal Liquid is optimal for sealing, repairing, and weatherizing concrete. It works by sealing out air, water, and moisture and is mildew, chemical, and UV resistant. You can either brush, roll, dip or pour the liquid directly onto the concrete surface.
Flex Seal will not stick to concrete that is excessively oily, greasy, wet, dusty, or covered in loose flaking paint. It also struggles to adhere to non-porous and repellent materials like silicone, polypropylene, polyethylene plastics, and highly plasticized surfaces.
Q: How long will it last? A: Depending on the environment, coats added, and maintenance, many people have found Flex Seal will last for years without cracking, peeling, or losing any of its strength or sealing properties.
The best foundation sealer depends on whether you are sealing the exterior to block water from entering, or the interior to manage vapor and minor dampness.
Sealing the concrete foundation helps reduce capillary water intrusion and moisture vapor transmission, lowering humidity levels and creating a more stable environment for finishing. Without this step, finished materials can trap moisture against the concrete—creating ideal conditions for mold growth over time.
Epoxy Injection: A Solution
For most household, automotive, and outdoor repairs, Gorilla Waterproof Patch & Seal or dedicated polyurethane sealants (like Sikaflex) outperform Flex Seal. These alternatives provide stronger adhesion, superior UV resistance, and greater longevity, especially when dealing with high-pressure leaks or extreme weather.
Concrete sealers provide excellent stain resistance, but they require ongoing maintenance, can be slippery when wet, and risk trapping moisture.
Answer. Flex Seal is designed to be a waterproof sealant that can effectively block out water and moisture when applied correctly. While it is marketed as being highly effective for sealing leaks and cracks, the degree of waterproofing can depend on the application surface and conditions.
Water is the most common enemy of concrete surfaces. When water penetrates the surface of concrete, it can cause it to crack and weaken. This is especially true in colder climates where water can freeze and expand, creating even more damage.
Wipe off any dirt or dust from your surface. If the dirt is a little hard to get off, wipe the surface down with a damp rag and cleaning solution. Flex Tip: If there's any rust on your surface, sand it off before moving ahead. Sanding your surface will increase adhesion for Flex Seal.
Coca-Cola does three main things to concrete: it slows down the curing process (acts as a retarder), etches the surface to expose decorative aggregate, and removes tough stains. This happens because of the soda's high sugar content and phosphoric acid.
Do not use Flex Seal on high-pressure or high-heat items (engines, radiators), gas tanks, potable water containers, or for long-term repairs on vinyl, PVC, or foam. It is not food-safe, and it does not bond well to greasy, oily, dirty, or certain nonporous surfaces like silicone, polypropylene, or polyethylene plastics.
For a permanent, waterproof, and structural foundation repair, the RadonSeal DIY Foundation Crack Repair Kit is highly rated. It uses professional-grade polyurethane injection to expand and fill the crack entirely, permanently sealing out water and soil gases like radon.
5 Most Affordable Options to Cover a Concrete Patio
"Poor man's concrete" refers to a budget-friendly, highly compacted mixture used to create a solid, semi-permanent base for driveways, sheds, or patios. It typically consists of a blend of gravel, coarse stone, sand, and stone dust.
The best concrete sealer depends on your specific surface. For driveways and patios, penetrating Silane-Siloxane options are highly recommended because they repel water and deicing salts. For decorative stamped concrete, Acrylic sealers bring out color and add a protective sheen.
The 90-minute rule is a longstanding concrete industry guideline stating that ready-mixed concrete should be completely discharged from the mixing truck within 90 minutes from the time water is first added to the cement. This limit ensures the mixture remains workable and achieves its full structural strength.
Flex Seal can last anywhere from a few months to several years. Its exact lifespan depends heavily on the severity of the environment, surface preparation, and whether it is used as a short-term patch or a long-term protective coating.
Yes, Flex Seal will adhere to concrete, provided the surface is completely clean, dry, and free of dirt, oil, or loose debris. It is designed to seep into pores, seal pinholes, and cure into a flexible, watertight rubberized coating.
Flex Seal usually becomes dry to the touch within 2-3 hours and fully cured within 24-48 hours. If your Flex Seal still feels sticky or tacky after application, it may not be fully cured. Please note that dry times can vary due to temperature, humidity, and thickness of the coat.
Achieving a permanent concrete crack repair requires addressing the root cause of the damage and selecting the correct material based on whether the crack is structural, moving, or strictly cosmetic.
Horizontal cracks are generally more serious than vertical cracks as they often indicate structural damage caused by external forces like uneven settling and hydrostatic pressure. On the other hand, vertical cracks, while typically less severe, can still allow water intrusion and should not be ignored.
Can you actually replace your home's foundation without lifting it? The answer is yes! However, it is hugely dependent on the style of foundation that your home has and the extent of the damage. We recommend consulting with a foundation professional in order to come up with a plan for your home.