While patios can be a beautiful and functional addition to the outdoor living space in your home, they often develop cracks. In order to fix the cracks in a concrete patio, you will need to follow these steps.
Step 1 - Determine the Crack Size
The size of the crack will determine the type of repair you make, and most importantly, the material you use to fill the crack.
There are two types of cracks in concrete. The first is a hairline crack, meaning it is very narrow and likely quite shallow. The second is a true crack, which can vary in size, but is deeper and wider.
Step 2 - Choose a Filling Material
The filling material for hairline cracks is likely to be a sand mixture of Portland cement. Epoxy fillers are another choice that may work, depending on the width of the crack.
Larger concrete cracks use either epoxy filler, sand cement mixture, or a coarse aggregate concrete, depending on the width and depth of the crack.
An epoxy filler is great for a crack that is one inch or less in width most of the way along, and has a fairly shallow depth.
Epoxy fillers are made specifically for concrete, and come in a gray color. They are packaged in a caulking tube and are applied by putting the tubes into a caulking gun.
The sand mixture of cement has no large aggregates (i.e.: gravel), so they fit better into narrow areas. The regular (large aggregate) concrete mixes are excellent for substantial cracks that require a great deal of fill.
Step 3 - Undercut Larger Cracks
A crack that is larger than a hairline crack may need to be “undercut” in order to get a good mend.
Using a hammer and chisel, enlarge the crack slightly, making the bottom of the crack wider than the top of the crack. This allows the concrete to adhere and remain in place better.
Step 4 - Clean the Area
The crack must be thoroughly cleaned, and any loose dirt, concrete, grout, or old filler needs to be removed. First, loosen old matter with a chisel. Then use a wire brush to brush away any old dirt, rocks, or debris from the crack.
Next, use a pressure hose or a garden hose with a nozzle to spray the crack. This serves two purposes—finishing the cleaning and wetting the area to help stop moisture leaching from the new concrete.
Step 5 - Prep the Crack
Use either a concrete adhesive in larger cracks or a chemical cleaner, such as phosphoric acid, to increase adhesive power of the concrete. Chemical cleaners are particularly effective on hairline and narrow cracks.
Step 6 - Install Repair Matter
Make a thick paste with the sand mix of cement and force it into the crack. Then smooth and finish with appropriate tools, or squeeze the epoxy filler from the caulking tube.
Make sure to force it into the crack and fill the bottom thoroughly.
For very large cracks, mix a thick paste of standard concrete and thoroughly fill the crack, forcing the mixture into the bottom of the crack first.
Step 7 - Finish
Epoxy fillers don’t require finishing, but concrete fillers should be finished with a wood float or metal trowel, and then covered for about five days, wetting the surface once a day.
Your cracked concrete patio is now mended and it's time to have that barbecue! Your guests will be none the wiser.