Two ways to solve puddle in garage floor

Q. Our garage floor is lower in the center than at the edges. As a result, a large puddle about 1-inch-deep forms whenever we bring a car inside with snow or ice that melts. Is there a way to increase the height of the floor center so that the water runs out the door? I am afraid that a layer of concrete would be too thin, especially at the edges, to support the weight of a car. Are there other floor-covering materials that would work?

Libertyville, Ill.

A. An experienced concrete contractor or mason who works with concrete should be able to clean the slab and apply a vinyl-reinforced mix that will stand the test of time. But does the concrete slab generally slope to the garage doors as it should? If not, this may not fix the drainage problem. There is another fix if the substrate is porous enough (not clay or heavy silt). Have a 24-inch-square hole cut in the lowest point of the concrete slab, and remove soil to a depth of 2 feet. Fill the hole with egg-size stones, and top it off by pouring concrete around an appropriate floor drain that you can buy in a plumbing-supply house or a building-supply store specializing in masonry supplies. You may be able to find an appropriate drain in hardware stores and home centers, but make sure it is substantial enough to handle the job at hand. If the holes are too small, they may freeze up and stop drainage; and there should not be a trap in which water will freeze.

Q. I know you addressed this problem often, but what I'm looking for is confirmation on a solution to our problem. Our house is a 1978 cape, which was built in an area with a very high water table. The water we get in the cellar never comes from the sidewalls, and there are no cracks in the floor itself. It always comes in from the perimeter, where the wall meets the floor. The floor crowns in the center, I presume from the hydrostatic pressure of 30 years, so the water circles the cellar to the sump-pump hole.

For years we had no water after we sank the hole fairly deep (the previous owners just let it come and go) and put patching cement around the perimeter. The exit was a makeshift rig of piping, so we hired someone to do a better job and have had problems ever since.

He raised the sump-pump level and put in a cement collar. Now the water doesn't get to the sump fast enough. In a heavy rain spell, the sump can run every minute for 10 to 15 seconds. We had a company that specializes in this problem give us an estimate of over $7,000 to rectify, a cost that is a bit over our budget. What we want to do is sink another hole on the other side of the cellar and install another pump and then install a battery backup pump for both sites.

Since we never get water if the water level stays lower than the cellar floor, would you think there is a less expensive and permanent solution?

Swanton, Vt.

A. Your plan is a good one that has worked in a number of situations similar to yours. The best way to build a sump is to cut a square hole 30 by 30 inches in the concrete. Excavate down to 30 inches, then lay 5 inches of egg-sized stones in the bottom, and place an 18-18-inch flue liner centered on the stone. The top of the flue liner should be 1 inch below the level of the existing concrete floor.

Fill the space around the flue liner with the same-sized stones but only to the bottom of the existing concrete. Patch the concrete with a concrete mix, using the top of the flue liner as a form. If done accurately, this patch will slope down toward the flue liner. This type of sump can handle very large amounts of water -- far more than a bucket with holes near the bottom.

Install a high-capacity quality submersible sump pump. Pipe it with the correct diameter pipe (no reduction in size) -- including a foot valve installed as the pump outlet -- straight up to the ceiling. Continue with a horizontal run to the outside through a band joist. The horizontal run should have a slight drop to the outside to make sure that the water in it drains out. The foot valve will keep the vertical leg filled with water. Place a concrete splash block under the discharge pipe to prevent erosion. If it works, and there is a very good chance that it will, it will cost a lot less than the proposed system.

Q. I have mold or mildew on only the north side of my house, which is shaded by a large pine tree. I also have the same problem on the north side of my garage, but there are no trees shading it. What causes this? What remedies can I use? Will mildew-resistant paint work?

Via e-mail

A. Mildew spores are always present in the air, all but in the most arid climates. The north side of buildings gets no reprieve from the sun, and any dampness hangs on for a while, causing the spores to stick to the siding. Power-washing with a mixture of one part fresh Clorox bleach to three parts water should get rid of the mildew. If it does not, power-wash again with equal parts water and bleach.

Follow this with a quality latex paint into which the paint store will mix a mildewcide. Be aware that this will last only a few years, depending on the ambient conditions where you live. (A damp site near water is a poor scenario.) Keep in mind that linseed oil-based paints are food for mildew spores; alkyd (synthetic oils) paints are better, but latex tops them all.

Q. I've a question about how to clean a sticky, oily and greasy mess over the cooking-range space microwave. This happens because of oily and greasy cooking and can't be cleaned with regular kitchen cleaners.

New Jersey

A. If you haven't tried 409, please do. It does a great job for me. But it may be the type of cooking you do that generates more greasy residue. If 409 does not succeed, you may want to try an oven cleaner, but first make sure it will not damage whatever finish is to be cleaned. Once you have it conquered, just keep it up by cleaning with 409 after each cooking session.

Q. I moved into my townhouse condominium 20 years ago. I have never finished the basement. There is what I think is called a French drain and a sump pump. The basement has never flooded. However, the cinderblock walls are increasingly wet, and friends have suggested I waterproof them. I am interested in finding out what you recommend.

Edison, N.J.

A. A French drain is an outside trench filled to the top with stones. You probably have either an open trench or a below-slab drain that captures the water and leads it to the sump. If the drain and sump pump keep your basement dry, all is going well. However, the cinderblock walls should never be waterproofed from inside. It would trap water within their cores and the water level, not having a way to drain, will rise. The only escape for the accumulated water is to evaporate in your living space. Humidity will increase to intolerable levels and molds will develop, endangering your health and making the dwelling uninhabitable. I have seen that happen in several cases.

The proper fix is to have the moisture problem taken care of from the outside. The grade around your townhouse should be checked. All flat or negative grades (grade sloping toward the house) should be raised to divert water away from the foundation. Downspouts must discharge on concrete or plastic splash blocks that move water a few feet away from the foundation. No depressions should be left near the foundation; they should be filled. Any appendages such as patio, walk, driveway, etc., that slope toward the house need to be resloped (if that is a problem, write again with specific details for a discussion.) This can be expensive, but it may be necessary.

If the foundation is so close to the ground now that it is not feasible to raise the grade, leaving the 8 inches of exposed foundation required by most building codes, you may need to use an alternative. Let me know if that applies to you, and I'll discuss it.

Safety tip

Please be sure to clear any snow accumulation around the exhaust vents of your heating appliances. If snow covers them, do not assume that the heat will clear the snow. Plugged vents may result in the accumulation of deadly carbon monoxide in the living spaces. This also applies to the vents of gas-fired dryers and any other fossil-fuel-burning appliances. And be sure that you have functional carbon-monoxide detectors in areas recommended by authorities. Check them often!

© 2008, United Feature Syndicate, Inc.