Don't Crack Up – Repair Cracks in Concrete Surfaces

All those cracks you've got in your concrete sidewalk or patio can be pretty dangerous. As you may know, homeowners are responsible for any injuries that occur on their property. Cracked sidewalks and patios are also unattractive, detracting from the beauty and value of your home.

Why does concrete crack? Repeated cycles of freezing and thawing will do it, as will the uneven settling of the soil underneath. But even if you're a beginning do-it-yourselfer, you can easily overcome the elements and repair the cracks yourself. To get started, visit your local True Value store for the materials you need, and follow our step-by-step guide to cement the deal.

Step 1: Damage Control - Remove the Damaged Concrete
Ready to get cracking? Grab a cold chisel and give the cracked or crumbling concrete a few good wallops, breaking it to a depth of about one inch below the surface.

Safety Alert! 

Flying cement pieces can have very sharp edges, so wear safety goggles and heavy gloves to protect your eyes and hands from airborne debris.

Step 2: Make the Cut - Undercut the Patch's Edge
Undercutting the edges of the area you'll be patching will help the patch adhere to the surface. Simply hold the chisel at an angle and chip away.

Step 3: Let's Talk Trash - Remove the Debris
Remove all the debris with a whisk broom and hose from the area until it's nice and clean. Keep it moist for several hours or overnight. Sponge up any standing water before you proceed.

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Step 4: A Batch of Patch - Mix the Patching Cement
In a small bucket, mix one part cement and three parts sand with enough water to make a stiff paste. In a separate container, mix a small amount of cement with more water - enough to make a cement ''paint.''

Step 5: Patch Things Up - Fill and Smooth Small Cracks
Remember those edges you undercut? Use the cement ''paint'' to coat those edges - almost like a primer. Then take the other mixture - the paste - and pack it firmly into the crack with a putty knife or trowel. Level the mixture with a straight-edged concrete-finishing trowel. Let the patch sit undisturbed for about one hour, then go over the entire surface with a float or trowel in a circular motion, blending it well with the surrounding surface.

• When you're applying the patch, make sure you cut deeply into the mixture to remove any air pockets

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Step 6: Go Deep - Filling Deep Cracks
Simple patching is for simple cracks. If the ones you've got are deep (in excess of 1/8'' wide and 1/2'' deep), it's time to bring out the heavy artillery - foam backer rods. Sold in a variety of lengths and diameters, foam backer rods are great for supporting the patch and preventing it from sinking as it dries and ages (especially useful for cracks around windows, doors and brick walls). Use a putty knife to force the flexible rod into the crack, placing it about 1/4'' below the surface. Now you can patch the area as before.

Step 7: How's the Patch Doing? Cure It.
After troweling the patch smooth, let it sit tight for a couple of hours, then cover it with a sheet of plastic (use bricks or rocks at the edges to weigh down the edges). Keep the area covered for an entire week, making sure to give it a spritz of water each day to keep it moist.

• Concrete is one of very few building materials that actually likes water - and the more of it, the better. While you obviously don't want to make repairs when it's soggy out, a gray, overcast day is just right.
• Here's a stop-gap repair solution if you're too busy to tackle the job right now: simply pack the crack with sand and seal it with waterproof tape - it will hold for the short term.
• Have any dry cement left over? In its powdered form, cement is easily ruined by moisture, so don't keep large inventories of it on hand - instead, try to buy just the amount you need. Store dry cement off the ground in a dry place, covering unopened bags with a plastic sheet or tarp. Opened bags should be placed inside larger plastic bags, and small amounts can be stored in an old coffee can with a plastic cover. If bagged cement contains unbreakable lumps, toss the whole bag. If you have several unopened bags, pile them on top of one another and place them close together in side-by-side piles.

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