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How to Permanently Repair Cracks in Concrete Floors

CrackWeld Concrete Floor Crack Repair Kit easily fills the full depth of fine stress cracks, hairline cracks, and fissures in concrete floors and a crack in foundation slab without the need to chisel or route the crack. CrackWeld quickly cures as a rigid compound that becomes stronger than the concrete itself! CrackWeld “welds” the concrete slab together providing flooring contractors and homeowners a state-of-the-art method for a proper repair of hairline cracks, wide cracks (up to 1/2″), spalling concrete, divots, and tack strip holes in concrete slabs.

Why Repairing a Crack in Foundation Slab Should Never Be Ignored

Cracks are the most common problem for indoor or outdoor concrete slabs, basement floors, driveways, garage floors, patios, pool decks, sidewalks, and parking areas. If a crack is not properly repaired, the situation will get much worse. Cracks left unattended cause further cracking, spalling, and disintegration of the concrete.

  • RAINWATER – Water gets to the reinforcing steel, makes it rust and expand, causing more cracking and concrete pop-outs.
  • FREEZE-THAW – Freeze-thaw cycle of trapped water widens concrete cracks.
  • SEEPAGE – The seepage of water, water vapor, and radon gas through cracks into homes and buildings.
  • TRAPPED MOISTURE – Moisture destroys flooring materials and may cause mold infestation.
  • EFFLORESCENCE – Water leaches out the concrete and causes efflorescence.
  • TRAFFIC – Vehicular traffic crumbles the edges of cracks.
  • EXPANSION/CONTRACTION – The cracks will get wider and longer due to the natural movement of concrete.
  • FLOORING AND OVERLAYS – Cracks propagate into rigid flooring tiles or concrete overlays.

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For secure and encrypted online processing of your order, simply add a product to your cart and checkout. Application and Coverage are detailed below.

CrackWeld Floor Repair Kit 2-Pack

CrackWeld PRO Floor Repair Kit

CrackWeld Floor Repair Kit 4-Pack

Shipping: Based on shipping by courier to the lower 48 states. CrackWeld is not sold in stores but is shipped directly from the factory to your door. Orders received by 2 pm ET are normally shipped the same day. For shipping to other states (AK, HI) please inquire first by e-mail or telephone. No expedited shipping for CrackWeld. Unopened kits in salable condition are returnable. Please review Product Returns.


CrackWeld® DIY Concrete Floor Repair Kits are designed for a quick and easy do-it-yourself application for homeowners. Each kit includes either two (2-pack) or four (4-pack) two-component CrackWeld cartridges, as well as mixing nozzles, a bag of silica sand, and other accessories. For full-depth repair of a standard 4” slab, each CrackWeld kit will repair

CrackWeld® 2-Pack: Up to 50 ft. of a 1/16” crack or 25 ft. of a 1/8″ crack

CrackWeld® 4-Pack: Up to 100 ft. of a 1/16” crack or 50 ft. of a 1/8″ crack

Tools Needed – caulking gun, paint scraper or trowel, and sandpaper (80 grit).

Color – Cured product is grey. Broadcasting sand over CrackWeld (silica sand is included) before it cures will result in a lighter gray color, but will not affect product performance in any way. UV exposure may lighten the color. Sanding and/or grinding the repair flush with the slab will reduce the polymer’s exposure to the sun. Adding sand to the surface allows the repair to hold stain or paint.

“I used your CrackWeld 4-pack to fill many hairline cracks and several 1/4 inch cracks on my driveway and garage. … My driveway and garage are over 30 years old and some of my neighbors, in the last few years had spent thousands of dollars to have their driveway repaired because of cracks. I am glad I found your product … I will be buying more CrackWeld to do some cracks in my basement too…” – Dan B., WI

“I live in San Juan Capistrano, CA and a few days ago we had a small 3.6 earthquake and this is about a week after I used the CrackWeld to fill small and large cracks in my garage concrete.  I checked the cracks after I got home from work and no separation and the seal looked just like it was before the quake…” – Romeo F., CA

See more CrackWeld Testimonials

The CrackWeld® Advantages for Repairing a Crack in Foundation Slab

  • NO ROUTING NEEDED –Eliminates the need for a cold chisel or grinding disk.
  • FILL HAIRLINE CRACKS – Low viscosity, self-levels. Needle nozzles are included for hairline crack repair.
  • FAST CURING – Cures rigid in 15 minutes for overlays, flooring, paint, heavy traffic.
  • STRONGER THAN CONCRETE – Bonds concrete to prevent elongation and yawning of cracks.
  • FREEZING – Can be applied in sub-freezing temperatures.

CrackWeld® is a two-component compound. When ejected out of the cartridge than through the mixing nozzle, it fills the crack, reacts, and quickly cures. Similar to epoxy, but only 1/10 as vicious, chasing (widening) the crack is not needed. The compound bonds with sand to form an indestructible, impermeable mass inside cracks, spalls, or holes. Water, vapor, or gases can not penetrate. It is also a structural repair – it stops the crack from further movement.

CrackWeld offers a rigid repair for random hairline cracks and fissures. It can also be used for repairing larger (or wider) stress cracks as well. CrackWeld is not suitable for joints that require flexibility like expansion control joints (saw cuts) or floor-to-wall joints of basement floating slabs. For sealing cold joints (cove joint), expansion joints, and floor-to-wall joints that require flexibility use ElastiPoxy Joint & Gap Filler Kit.

Customers’ feedback and tips on Repairing Cracks in Concrete Walls and Floors

Easy Application

Easy Enough For A Novice – The inside of the crack must be clean and dry. (Some contractors first place duct tape on both sides of the crack to make cleanup easier, particularly on rough surfaces.) Just follow these basic steps:

  1. Inject the CrackWeld resin into the crack to wet the surfaces and make them tacky.
  2. Push dry silica sand into the crack to fill it.
  3. Thoroughly saturate the sand with CrackWeld resin to fill it to the surface.
  4. In 10 to 15 minutes, scrape off the surface to make it level and use sandpaper for a neat appearance.

Hairline cracks that are too narrow for sand are filled and repaired with two passes of the CrackWeld resin. To repair wide cracks or cracks with a void underneath, first, fill the crack partially with sand to prevent the CrackWeld resin from running out. If additional sand is needed, use DRY graded sand (no fines) or ideally, sandblasting sand with granulation like table sugar (30 to 40 grit).

CrackWeld Cures Fast – Maintain a steady flow of CrackWeld through the mixing nozzle or it may become plugged after a minute or two! After a stoppage, purge the mixer into a disposable cup. To minimize stoppages, repair small sections of the crack at a time (5-10 ft. or use up the whole cartridge). Fill the crack with sand in 2-3 minutes after priming while the compound is still tacky. For longer cracks, recruit a helper to pour the sand, help scrape, or sand afterward.

The Wrong Way to Repair Cracks in Concrete Floors

Self-Leveling Polyurethane Caulk – Covering the crack with caulk is cheap and easy, but short-term. Water wicking through the concrete or trapped water vapor will weaken its bond to concrete, which may show up as efflorescence. The caulk will not last in traffic. After a couple of years, the caulk gets loose and can be easily peeled off.

Hydraulic Cement – Hydraulic cement is only a temporary fix. Yes, it has waterproofing qualities, but it does not bond well to concrete – that’s why you have to chisel out the crack as an inverted V-groove to hold it in place. It also is more rigid than concrete. However, concrete continually moves, shrinks, and expands which loosens the stiff hydraulic cement. After a few years, water seepage and likely also efflorescence will appear around the edges of the plug.

For Contractors – CrackWeld PRO Floor Repair Kit

The Complete Contractor Toolkit – The CrackWeld® PRO Concrete Floor Repair Kits are for contractors or homeowners with extensive slab cracks. The two-component CrackWeld compound is packaged in dual-tube cartridges. Each kit is complete and “ready to go.” It includes a professional dual-cartridge gun, as well as mixing nozzles, a bag of silica sand, and other accessories.

Coverage – For full-depth repair of a standard 4” slab, each CrackWeld Pro kit will repair up to 100 ft. of a 1/16” crack or 50 ft. of a 1/8″ crack.

Purchasing Extra Material – In case additional materials are needed, purchase our CrackWeld® PRO Consumables Kit. The consumables kit is similar to the full PRO kit except for the dual-cartridge gun and gloves.