Even the strongest walls may need attention or repair from time to time. Here's how you can patch and tuckpoint wall cracks.
About this Project
You may expect your walls to simply hold strong forever, but even those items need maintenance at times. Areas that are exposed to the elements, such as mortar joints, actually need to be tuckpointed every 30 years or so.
Temperature changes can affect your walls, causing expansion and contraction - creating cracks. These cracks are usually uniform in width and creep along the joints between bricks or blocks.
Cracks also happen from uneven settling of footings. You can find settling cracks tapering along vertical paths, wide at the top and fading to hairline cracks near the bottom.
Horizontal cracking may appear in basement walls made of concrete blocks. Usually the cause is pressure from backfill soil and water pushing in from the outside. If the wall bulges noticeably, you have a serious problem. You may need to dig out the backfill and re-lay the blocks-a job most suited to a professional contractor. The same procedures are used to repair a cracked mortar line and for tuckpointing. For a long-lasting tuckpointing job, chisel or grind out all the joints. If your grout lines generally are worn and cracking, you need to tuckpoint the entire area or the problem will worsen rapidly. Tuckpointing is painstaking, slow work. It can be done from a ladder, but you'll find the work easier, and you'll do a better job, if you set up scaffolding.
Chisel out the joints: With a baby sledge and a cold chisel, remove mortar from joints to a depth of 3/8 to 1 inch. It is possible to tuckpoint without chiseling out old mortar, but the tuckpointing will not last as long. Because chips will fly as you work, wear safety goggles and heavy gloves.
OR use a grinder: If you need to work on a large area, rent or purchase a 4-inch grinder to efficiently remove old mortar. Whichever method you use, if the joint crumbles easily all the way through the wall, tear down the whole section and re-lay the bricks with new mortar. Tuckpointing by itself will not add strength to weak masonry joints.
Use the point of a cold chisel or the tip of a pointed trowel to scrape away patches of mortar that remain after chiseling or grinding. Briskly sweep away debris with a stiff whisk broom. Mix the mortar using 1 part Portland cement to 2 parts masonry sand and enough water to form a puttylike consistency (see Working with Mortar, Related Projects).
Load an upside-down trowel with mortar and hold it against the wall. With a 3/8-inch back filler, force the mortar into the joints. Fill the head (vertical) joints first, then the bed (horizontal) joints. It will take practice before you can tuckpoint without dropping mortar or smearing bricks.
4. Strike the joint
Use a damp sponge to wipe away excess mortar while it is still wet. Brush the joints to remove mortar crumbs. Correct timing is essential for striking the joints. The mortar should be stiff, but not hard. Choose the appearance of your joint from those shown in Choosing a Mortar Joint, Related Projects.
To ensure that your joints are watertight, strike them a second time, making sure they seal tightly against the bricks. Let the mortar set up somewhat, then brush away crumbs with a stiff brush. Scrub mortar stains off the wall within 24 hours.