A few points up-front: 1) if the water is actively flowing our of the cracks/walls, it will push aside the wet epoxy and open up an unobstructed path into your basement. 2) if sealing a crack or joint (commonly where the wall meets the floor), sealing one area may just move the water flow to the next path of least resistance - i.e. several inches or feet farther along the wall - perhaps to an area that was leak free before. You'll also need to coat perhaps six inches or so beyond the edges of the 'crack' or seam (up and outward). THE SURFACES MUST BE VERY VERY CLEAN - YOU NEED TO GET MAX EPOXY BOND. USE OUR ESP 155 EPOXY CEMENT SEALER AND PRMER TO PROVIDE MAX BOND OF THE EPOXY/FIBERGLASS TO THE CEMENT (corro-coat fc2100A fiber-reinforce epoxy paint) 4) If your floor has been coated or sealed before you might have problems with a new sealing job. Some concrete floors are sealed with a 'waterglass' or wax/silicon based sealer. Not much sticks to these kind of surface especially when seeking an extremely tight and waterproof bond. Our Bio Vee Seal will also not work, as it will not soak into the concrete. Nothing sticks to 'silicon seal' either. Putting epoxy over an existing paint or epoxy means the bond will be only as good as it was on the old coating, now covered with the new epoxy. 5) If your basement is damp and musty, but has no obvious cracks or seams to seal, then the easiest and cheapest sealer is our non-epoxy Bio Vee Seal. (this product has its own web site - click here). This product soaks into the concrete and forms crystals inside the pore spaces of the concrete, thus reducing porosity and permeability. It leaves nothing on the surface of the concrete. 6) If you have water seeping through a CINDER BLOCK concrete wall, that is another issue. Most basement walls are pour concrete but some are stacked concrete blocks. These stacked block walls are cement and fly ash and tend to have large spaces ("vugs") or openings on the surface. The size of these holes varies from manufacturer to manufacturer. In any event, these 'openings' make concrete blocks difficult to waterproof and seal. Thin products drain out and paints of all kinds never seem to completely fill and seal the holes.  The best product to seal cinder block walls is our EPOXY CREAM product. It is a toothpaste like thickened epoxy gel that easily slides off a putty knife like a hot knife through butter. This makes it easy to fill cinder block vugs and give the block a smooth surface. Find EPOXY CREAM in our industrial catalog - CLICK HERE IN A NUT SHELL  ---  Wall - Floor Seam Leak Repair The fix is almost like doing a fiberglass cloth and epoxy  seam/repair on a boat or a drywall seam in your house.  When the surface is dry,  clean really well to get off all dirt, clay, etc. Start with an epoxy primer/sealer on the exposed concrete (ESP 155). Paint on a layer of FC 2100 /kevlar epoxy along the seam and up the wall a few inches and out onto the floor a few inches. Press into it a layer of fiberglass cloth, extending up the wall and out onto the floor. Add more epoxy over the fiberglass cloth to saturate it with epoxy resin. Generally add a second optional layer of fiberglass cloth over the saturated first layer and saturate it too (two or more layers of cloth are better than one). Hours or days later come back and brush on a fresh lower of epoxy over the first fiberglass/epoxy layer. This is to make sure you get any thin spots, missed areas or tiny pin holes covered with epoxy. Now wait for the next big rain storm. If you see areas of small leaks over your repair, repeat with more epoxy or more epoxy and fiberglass cloth. You cannot just fix the immediate area around the original leak - the leak will just move down the wall/floor a few feet. You generally have to do the entire wall/floor length. Order our 1.5 gal Kevlar (tm) ceramic gray wet surface epoxy - Corro Coat FC 2100A  (click here to buy  - under EPOXY PAINTS). The 3 inch or better yet, the 4 inch wide fiberglass cloth (4 inch by 50 yards) is in the ACCESSORY section.) Optional "stab brushes" (see below) to push epoxy into crack/seam etc. Total cost is about $400 Things go better with Fiberglass Cloth We sell 9 oz fiberglass cloth in 50 yard rolls. Three inch or four inch wide fiberglass "tape". The "tape" is easier for beginners to work with than big sheets of fiberglass - (saturate with epoxy and apply like strips of duct tape). Use for boat-building and/or repair, epoxy pipe wrap projects, and basement leak repair (sort of a dry-wall tape system but using fiberglass cloth and epoxy. Note that when using epoxy and fiberglass cloth, the strength comes from the fiberglass cloth and not the epoxy. - Order the 3 inch or 4 inch fiberglass rolls at either of our on-line stores or call to order your epoxy and cloth - 603 - 435 -7199.    EPOXY CREAM in our industrial catalog - CLICK HERE - for leaking Cinder Block wall sealing Top 7 List Of Reasons for Using Our Leak Sealing Epoxies: 1) Special epoxy that will bond to damp surfaces (fc 2100A) 2) Epoxy contains Kevlar (tm) fibers for gap filling (fc 2100A) 3) 24/7 phone and email support 4) Honest and complete info (pro and con) on this site. You get the FULL story. 5) Sold by an epoxy coating company and not a sales/marketing firm 6) Made in the USA 7) We appreciate your interest and thank you sincerely for your business!   Why Corro Coat FC 2100A epoxy is the BEST in its class: 1. Gap filling Kevar (tm) based epoxy paint  2) can be applied underwater 3) special high end curing agents allow shipping by air 4) no nonyl phenol 5) cycloaliphatic formulation 6) no odor or solvents 7) strong user support / feedback 8) 24/7 support NO SALES TAX - You are shopping in TAX FREE New Hampshire - New England's "Granite State"       OK - here we go: There are lots of wet basement  foundation problems and they are all different. The most common are water escaping through the walls or floors, coming out of obvious cracks and coming out of floor wall seam.. The floors are always poured concrete, but the walls could be block or poured concrete. For the moment, we'll consider the poured walls. WATER PASSING THROUGH THE WALL/FLOOR CONCRETE FOUNDATION CRACK Contrary to what many people think, cement is rather porous and permeable. It can fill with water, and worse yet, water can pass through it, migrating into your basement. The result and be dark, damp concrete, a musty smell, or even liquid water after a good rainstorm or winter melt. While not always present, but when it is, not a good sign, is what looks like white dust or powder on the walls or floor. These are mineral crystals that were in the water the migrated through the concrete and were left behind when the water evaporated inside your basement. The minerals could come for the surrounding groundwater or perhaps even out of the cement itself. It is possible that your concrete walls are literally dissolving away. If so, the leaking will only get worse year after year. TWO EXAMPLES OF MINERAL SALTS/CRYSTALS ON WALLS FROM WATER PASSING THROUGH THE WALLS - NOTE CONCRETE CRACK REPAIR ON LEFT PICTURE The bad news is that as these crystals grow and form, they can generate up to 2000 pounds of pressure, popping off just about any coating or sealer applied over them (more so because these coatings are probably applied to a crumbling, weak or dirty surface to begin with).                           NEW MINERAL GROWTH THAT 'POPPED' OFF THE CLEAR EPOXY SEALER After cleaning the surface, the best attempt to fix this problem is our Bio Vee Seal. This product is designed to soak into the concrete and form its own crystals below the surface, thus ‘clogging' up the concrete and reducing the ability of the water to move through the concrete. This is an easy and cheap, first attempt to fix the problem. In addition to, or instead of, the next option is to apply two coats (always better than one coat!) of a watery, thin epoxy. Generally this epoxy is thinned with solvent to help it ‘penetrate' into the concrete a little bit, giving it a better, stronger bond. This would be our ESP 155 solvent thinned epoxy or our solvent free Low V epoxy which you have (or have not) added some solvent. We suggest two coats because it is most likely that with just one coat there will be tiny ‘pinholes' where the coating is missing. We've seen the water literally ‘jet' out of these invisible coating pinholes. With two coatings hopefully these thin or missed spots are covered in the second coating.                                   FRESH MINERAL SALTS/CRYSTALS THAT DEVELOPED THROUGH PINHOLES AND THIN SPOTS IN THE EPOXY COATING ON CONCRETE WALL   The next step (some folks just use the sealer above or this thick epoxy as a one coat fix) is a thicker epoxy paint. This step gives a thicker overall coating to the wall or floor, and these epoxies are often pigmented (compared to the clear coatings above). Usually the thick, Kevlar (tm) reinforced epoxy paint - Corro Coat fc2100A is best. The fibers bridge gaps and this epoxy sticks to wet or damp surfaces. This is the same epoxy recommended for leaking floor - wall joints (see below). WALL/FLOOR CONCRETE CRACK REPAIR Here again you have options. The most simple and direct is to simply apply a thick goopy epoxy gel/paste (or even a less thick epoxy paint) into and along the crack. Our kevlar (tm) re-enforced thick Corro Coat FC 2100 A (even bonds to wet surfaces) is a favorite here.  Even just one tiny pinhole left behind and the water will squirt out like a jet. The best plan is therefore 2 or 3 coats of the epoxy. It is also an option to use a thin or solvent thinned epoxy (Our ESP 155)  as the first coat (as a primer or sealer) as this thinner first coat will probably "soak" in a bit and provide a stronger bond to the thicker top coat epoxy (as well as help prevent those nasty pinholes in the thicker coating).       CONCRETE CRACK REPAIR WITH THICK EPOXY On larger cracks I have been successful using fiberglass cloth and epoxy resin (like building a boat) to ‘tape' over the crack. This is sort of like using a ‘band-aid' and first aid cream, instead of just the first aid cream on the crack. FLOOR/WALL SEAMS LEAK REPAIR Leaks along the floor and wall seam are very common. The bad news is that if you just fix the area around the current leak, the leak will probably just move farther along to the next ‘weak link'. You may have to seal the entire length of the wall, or perhaps all the way around the entire room. The first step is to get it area as dry and clean as you can. Lots of dirt/mud gets drawn in with the water and you cannot seal or coat the dirt and expect it to be effective. The best fix approach here is to first ‘paint' the seam (about 4-6 inches out onto the floor and about 4-6 inches up the wall) with an epoxy paint (like those mentioned above). A coat or two usually stops the leak. After this first coat of epoxy has cured, the next move is to apply more epoxy with two layers of fiberglass cloth along the seam and on top of the first layer of epoxy (sort of like ‘taping' a drywall seam). There will be pinholes and ‘leaks' in the cloth/epoxy layer (especially in rough surface areas, corners, and at the ends/beginnings of the strips of fiberglass cloth). So, once the epoxy/cloth layer has cured, one more coating of the same epoxy is brushed over the epoxy/cloth layer. This usually does the trick, albeit, a 3 coat system. FIXING THE CONCRETE FLOOR WALL SEAM WITH GRAY Corro Coat  FC2100A EPOXY WITH FIBERGLASS CLOTH Generally folks order the 1.5 gal kit of the Corro Coat fc 2100 A - a roll of the 4 inch wide fiberglass cloth - 1 1/2 gal unit of ESP 155 epoxy sealer and primer (not for sale in Calif.) user feedback: "You prepared me well. I would just say to have many rags, garbage bags and several sets of disposable gloves. Wear old clothes. Those items made it much easier. If you're in a crawl space, it's probably a good idea to wear a mask and cap. I made the mix in a plastic pitcher and poured it from there. For some areas,I dipped the brush in the mixture and spread it on. After I was finished, I wrapped everything up in a garbage bag and threw it all out, took a shower andwas good to go." - Donny                         2100A epoxy and fiberglass basement leak repair     Epoxy "Stab Brush" --  "Regular Brush" Use with products on this page buy separately or include with your order STAB BRUSH - 3 inch wide with 3/4 inch bristles. Most epoxies are too thick for a regular brush. Stab brushes allow you to push and move the epoxy around and 'stab' or poke it into cracks, voids, and corners REGULAR BRUSH - 2 inch wide and extra thick with synthetic bristles. Use with varnish, paints and thin epoxies. Priced for disposable use.   Goto our 3rd party storefront and purchase in the MISC SECTION Stab Brushes are a good way to apply thick epoxy to cracks and fiberglass cloth (Cinder) BLOCK WALLS The density and particle size in the blocks that make up these walls varies a lot. Generally the Bio Vee Seal will not work as the gaps and voids it tries to fill are too big. The best attempt at a fix here is simply several coats of epoxy paint or resin. It will take more than one plus coats to seal it completely as there is no way you will able to fill all the ‘indents'/voids/spaces that make up the surface with just one roller or brush applied coat.