Q: I have a 200-square-foot, partially covered concrete patio. The concrete surface is in pretty good condition, except for several dark stains and several minor cracks. I would like to resurface this area or cover the concrete with something to improve its looks. I looked into outdoor carpeting with rubber matting, but these options were either ugly or expensive. I had considered outdoor tile, but would like your advice. What would you suggest that would look nice and not be too expensive?
A: Your best bet for ease of application and durability at an affordable price is to resurface the concrete. There are a variety of materials available for patching and resurfacing concrete: portland cement concrete, bituminous pavement patching mixture, fast-setting cement-like materials and polymer concrete. However, polymer materials are most effective for small repairs because they are two to four times stronger than the concrete to which they are applied. Polymer-based concrete resurfacers are formulated to transform cracked, spalled, weatherworn concrete to like-new condition.
For a successful resurfacing job, proper preparation of the existing surface is critical. Start with a thorough cleaning. It's best to use a pressure washer, available for rent at an equipment rental outlet, to rinse the concrete. Use a stiff-bristle brush or push broom to sweep away all dirt, dust and debris. Grease and oil stains should be removed by washing with a solution of trisodium phosphate, which is available from a paint dealer or home center. Don't use any solvent, sealer or primer. Allow the surface to dry thoroughly.
Fine hairline cracks can be sealed by injecting or pouring liquid structural adhesive into the crack. Or use one of the polymer patching products for repairing cracks up to 1/8-inch wide. Mix according to manufacturer's directions, and force as a thick paste into the cracks with a putty knife. For larger cracks up to 1/2-inch wide, use concrete-repair caulk. Squeeze the caulk into the cracks with a caulking gun, and smooth it with a putty knife. Softer concrete around cracks and holes should be chipped back several inches to expose strong hard concrete. This ensures a good bond with the patching material. The opening should be thoroughly swept with a stiff-bristle brush and vacuumed to remove all chips and residue. Prime the area with liquid resin, then fill with patching compound, and trowel smooth.
Large concrete slabs are typically divided into sections by expansion joints, which help control cracking. The 1/2- to 3/4-inch-wide joints are usually filled with asphalt-saturated felt, a 1-by-4 piece of wood or plastic channel. These joints must remain exposed to allow the slab to expand and contract; don't cover them with a cement resurfacing product. Mask each expansion joint with a strip of duct tape.
Once the slab is clean, cracks repaired and the expansion joints protected, you are ready for the application of new resurfacing material. Do not take shortcuts trying to speed up the job; they will only jeopardize the success of your project. Most resurfacing products are dry concrete mixes that are blended with water immediately before use. They must be mixed quickly and then applied immediately. The work isn't particularly difficult, but the pace is frenetic. Two people working in concert is usually better than going it alone.
When you pour the resurfacing mixture on the concrete, one can work at spreading it while a partner mixes the next batch. Typically you will have less than 30 minutes to spread the resurfacing material before it hardens.
There are numerous products from which to choose. One company, Macklanburg-Duncan of Oklahoma City, makes a line of specialized concrete-repair products marketed under the brand name Mr. Mac's. A number of Mr. Mac's products contain a polymer modifier to give them more flexibility than conventional concrete mix or sand mix. Mr. Mac's is available through home centers, paint outlets and hardware stores. If you have difficulty locating this product line, contact the company at 1-800-348-3571.
Ardex All-Purpose Concrete Resurfacer is another product available through home centers, hardware and paint stores. It is made of portland cement and high-performance polymers. Before buying any concrete-repair or concrete-resurfacing product, read directions to make sure it is suitable for your project.
Q: We have a garage that we want to convert into an extra room. The concrete floor is not level. Is there any way for a do-it-yourselfer to correct this before we proceed with a remodeling project?
A: If you have just a few low spots, leveling the floor is a job you can easily do yourself. Place a long, straight 2-by-4 on the floor of your garage and shine a flashlight at the floor on the other side of the board. Mark with a pencil the areas where the light shines through any gaps between the wood and the floor. Do this for the entire floor to identify the low spots.
Once these low areas are marked, clean them with detergent or trisodium phosphate and water to remove any grease or oil. Then mix six parts water and one part muriatic acid in a plastic watering can and use it to etch the concrete low spots. Scrub with a stiff-bristle broom or brush, then rinse with clean water. Wear protective clothing, gloves and a face shield while working with the acid.
After all the low spots have been treated, fill them with a self-leveling latex modified mortar compound, available from home centers or from a concrete supply company. Be sure to read directions carefully. Some mortar mixes require a separate bonding agent.
Pour the mixed mortar into the center of each low spot, using enough to completely fill it. As the name implies, the mortar will level itself, but you may have to smooth it around the edges. If the floor is sloped, or has cracks and dips all over it, you should consider hiring a professional contractor.
It takes experience and special tools to apply self-leveling concrete over a large area. If the work is extensive, it can be less expensive to tear up the existing floor and replace it.
Q: We purchased a house where the bedroom is wallpapered in gigantic blue roses. This definitely does not suit my tastes or my modern furniture. Can I paint this wall without removing the wallpaper?
A: Although I prefer to remove old wallpaper before painting or adding new paper, it is possible to paint over existing wallpaper if your wall covering meets the following criteria: It is not a textured or flocked paper; and the existing paper is firmly attached to the wall and has smooth seams.
If there are a few peeling edges, these can be repaired prior to painting. You can reattach any loose edges with a seam glue available from your wallpaper dealer, or you can scrape off loose areas with a razor blade and fill the slightly recessed spots with spackling compound, then sand the surface.
If your wall covering has any sheen, first wipe it with mineral spirits to remove the filmy topcoat. A glossy vinyl should be treated with a special primer that provides a good bond for slick surfaces and has a stain killer. A dull covering that is made of paper can simply be primed and painted.
I would recommend, however, that before you proceed you should consider removing the existing covering. There are a number of solutions and tools on the market for removing wallpaper. Check with your local wallpaper dealer. You may be much more satisfied working with the original wall surface than painting over the paper.
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