Q. We contracted with a company to waterproof our basement walls, and ended up with our basement floor collapsing at least three inches. There had been space underneath and the company we hired did not test before drilling around the floor to lay pipes.

The company responded to our complaint by breaking up the existing basement floor and pouring a new concrete floor by wheelbarrow. You would know if you saw the results that the company was not qualified to do the work. The floor is bumpy in some places and has low spots in others. It is roughly finished and patched in many areas. It would be impossible to tile or even carpet it to get the recreation room we once had.

My question is: Have you any ideas or advice to give us on resurfacing the floor, instead of breaking the concrete up again and starting from scratch?

A. You have several options that should be less of an investment than starting from scratch. First, it is important that you test for moisture penetration. Dampness can migrate up through the concrete slab. This won't happen in a properly poured concrete floor--gravel or a vapor barrier under the slab will stop the moisture. But in areas with poor drainage or with slabs poured directly on the soil, dampness may be persistent.

Check for moisture in two or three spots around the room, using 2-by-2-foot sheets of polyethylene plastic placed flat on the floor, the edges sealed with duct tape. After 24 hours, peel up the plastic. If the covered areas are damp or darkened by moisture, you will be more limited in flooring applications than if the areas remain dry.

Assuming that moisture is no longer prevalent, application of a mortar-based interior floor leveler may be the solution to your problem. A floor leveler is generally designed to adhere to concrete and wood and can also be used to patch cracks and fill low spots. It is one of the best techniques to ensure a smooth, compatible surface for tile, vinyl, carpet and even wood flooring installations. A good floor leveler sets hard in 30 minutes and will not shrink or crack.

In preparation, all dirt, dust or loose materials on the existing surface need to be removed. A good floor leveler can be used on below-grade surfaces such as yours. Be careful: There should be no presence of moisture or continued dampness on the concrete surface.

Floor levelers are applied like pre-mixed concrete. You only need to add water and stir and mix it to a creamy blend. Most manufacturers recommend that you wet the concrete floor or wood substrate before application to improve adhesion and retard suction. Then pour the mixed compound directly onto the uneven or cracked surface and spread with a steel trowel. Allow 15 or 20 minutes for the mixture to set before finishing with a steel trowel. The finish can be sanded when it is dry.

If your moisture test revealed dampness in the concrete, you should consider other options, which include waterproofing. One is to lay a polyethylene moisture barrier over the entire floor, overlapping separate sheets by 12 inches. Another waterproofing method is to spread an asphalt sealer over the concrete. Some flooring consultants recommend both, the asphalt sealer covered with 6-mil polyethylene sheeting.

If the ceiling height allows, fasten pressure-treated 2-by-4s on edge around the perimeter of the room, and at 16-inch intervals (2-by-4 sleepers) across the floor, shimming them where necessary to level the new floor. Plywood subflooring is then laid perpendicular across the sleepers. The addition of fiberglass insulation between the sleepers, before installing the subflooring, will provide added warmth to your floor.

Once the subflooring has been installed you have many options on floor coverings: tile, carpet, vinyl, wood. Another option would be to install a floating laminated wood flooring system. In this system, laminated planks, usually about one-half inch thick, are laid over a thin (one-eighth-inch) foam pad (6-mil polyethylene sheets or an asphalt sealer can be used to cover the concrete slab first as an added moisture barrier). Other than the glue used to secure each tongue-and-groove plank to the next, no other adhesive or nails are used.

I had concrete poured last fall for a patio and additional parking. The concrete goes up to the back of my house and the garage. There are expansion joints, but none along the house and the garage. The concrete developed a hairline crack in a section next to the garage.

What has me alarmed is that I have talked to another contractor who says that there should have been expansion joints put in along the house and the garage. This contractor says that the concrete freezing and expanding can eventually cause more cracks and even structural damage to my house. The original contractor denies this. Which is correct?

The second contractor is correct. An expansion joint where the slab abuts an existing structure is necessary. It allows for the expansion and contraction in a cement slab that occurs as temperatures vary. Lack of the expansion joint will cause your cement slab to crack.

The width of recommended expansion joints varies, depending on the length of the joint and your area's climate. Expansion joints are made using flexible materials--those that can be compressed and expanded over time without cracking. Sealant rather than grout is used because it is flexible and gives as needed. However, it must not be applied too thick (the depth should be no more than one-half the width of the joint) or it will lose its elasticity. Therefore a backer rod is recommended to partially fill the joint so that sealant can be properly applied on top of that. Backer rods are closed-cell, flexible polyethylene tubes, which are available in a variety of diameters.

Could you please provide more information on metal roofing materials, such as where they are available and who should install them. I recently read your article discussing this type of roofing.

The metal roofing article created numerous requests such as yours. Just recently, the Metal Roofing Alliance established a toll-free hot line for consumers with questions on residential metal roofing. Call 888-638-2576.

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