Repair or Remove a Sinking Porch Slab
QUESTION: My brick house is about 20 years old. It has a concrete porch about 5 feet square with steps going down to the backyard. The steps and the porch have settled and pulled away from the house, leaving about an 8-inch gap at the top. The foundation goes deep underground. Even if I could find a house jack big enough, I couldn’t fill in under the porch foundation. There’s no opening under the porch slab and steps to build a form. What can I do to solve this problem besides move?
ANSWER: If you are certain the porch is not still settling (if the gap is not getting wider year by year), you can fill in the gap between the steps and the house foundation wall starting at the bottom where the gap is narrowest. Wedge a 2-by-8 board vertically against each end of the steps to hold the repair concrete in place until it sets. Carefully fill the space between the house and the porch with concrete and compact it by poking it with a hoe handle to make certain it has completely filled the gap.
Finish the job by smoothing the top flush to the top step. Where the edge of the patching meets the wall, finish the joint with an edging tool. This leaves space for final sealing with a good grade of silicone caulk. If the joint continues to enlarge, the only permanent cure is to remove the porch entirely and rebuild it on proper fill.
Chemicals Can Cause Concrete Breakdown
Q: The concrete walkway around our built-in swimming pool seems to be flaking off. That is, when we sweep around the pool we have a lot of dust. Is it normal for concrete to break down like this? Is there anything we can do to stop it?
A: The condition you describe is called dusting. It usually occurs within the first several months of when concrete is installed. Several things can cause it, such as using a concrete mix that is too wet, allowing the surface to dry too rapidly, freezing temperatures before the concrete is cured.
Since the concrete is seven years old, we suspect it’s being caused by the pool water being splashed on the concrete. Chemicals in the pool water, such as chlorine, may be reacting with the concrete.
Try the following. Remove the dust and clean the walkway by scrubbing the surface with a stiff bristle broom, then hose off the accumulated dust. Let the walkway dry, and be careful not to splash pool water on it. Next, coat the concrete with a sealer that contains methyl methacrylate or silane.
One such concrete sealer is Pakmix, and it’s sold at home centers and masonry supply yards. For information, write Pakmix Inc., 873 Western Ave., Toledo, OH 43609.
Pump In Dry Air to End Mildew Problem
Q: Our 16-year-old painted redwood house has a terrible mildew problem, even during periods of bright sunshine. The inside of the house seems to sweat and the inside surfaces of the window frames are peeling. We would eventually like to have aluminum siding, but first we must solve the mildew problem. What do you suggest?
A: You have probably checked the obvious sources of moisture such as a lack of kitchen and bath fans and poor exterior landscaping that may allow rainwater to run into your basement and crawl space. Moisture rising from these areas is a common source of this problem.
If you do not know the source of excessive moisture in the house, you should introduce some dry air from the outside. There are a number of air exchangers on the market that are designed for do-it-yourself installation and are reasonably priced. These units usually have a fan that moves fresh air in, over or through ducts that are heated by heated air from the interior of the house moving out through the same unit.
This is not only a solution for excess interior moisture but an answer to supertight homes that suffer a lack of fresh breathing air.
Ventilation Can Help End Condensation Woes
Q: Our house was built about 1925, with a cypress shingle roof installed on 1-by-4-inch wood strips, 8-inches on center. The attic has no ventilation or insulation. I would like to install a painted sheetmetal roof over the wood strips. My concern is condensation on the bottom of the sheetmetal. What is the best way to do this?
A: Providing ventilation and a vapor barrier in the attic will control the moisture buildup and resulting attic condensation. You should also insulate the attic. Even though your house is located in a warm climate, insulation is cost-effective and will help make the house more comfortable.
During the summer, it’s possible for the attic temperature to reach as high as 150 degrees Fahrenheit. Attic insulation and ventilation helps reduce the heat load on the ceilings of the rooms below. It also helps reduce air-conditioning costs.
Check with your local utility company to determine the recommended amount of insulation for your attic. It is more practical to install insulation batts with an attached vapor barrier rather than use a separate vapor barrier. Place the batts on the attic floor between the joists with the vapor barrier facing toward the rooms below.
You should also use at least two vent openings to allow for air movement. Installing watertight vents in the sheetmetal roof may be difficult, so your best bet would probably be to use gable vents. A combination of gable and soffit vents would be even more effective.
Since there will be a vapor barrier in the attic, the size of the vent openings can be less than it would be without a vapor barrier. Remember, the vent’s effective area is less than its actual opening. Screens or louvers can reduce airflow through a vent by as much as 50%. The effective area should be at least 1/300th of the attic floor area.
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To submit a question, write to Popular Mechanics, Reader Service Bureau, 224 W. 57th St., New York, N.Y. 10019. The most interesting questions will be answered in a future column.
For further information on any home problem, write to Popular Mechanics, Readers Service Bureau, 224 West 57th Street, New York, N.Y. 10019.
