Get an Expert to Test Ceiling for Asbestos

Question: I am concerned about a possible asbestos problem in our ceiling. Our home was built around 1969, and it has a type of ceiling finish known as popcorn or cottage cheese. The ceiling has become dirty and needs to be repainted. Can the ceiling be repainted, or should it be dealt with by some other means?

Answer: First, have the ceiling material tested to see if it contains asbestos. Just because asbestos was used for ceilings at the time your house was built doesn’t mean that your ceiling contains asbestos. Testing is recommended because of the expense involved in properly correcting the problem if the ceiling contains asbestos. If it does, then whatever action is taken is not a do-it-yourself task.

The procedures for working with asbestos-containing materials fall into three general categories: removal, encapsulation and enclosure. Painting would be considered encapsulating. However, before painting, the ceiling would have to be cleaned. This can cause particles of asbestos to loosen and fall.

Also, several asbestos consultants with whom we discussed this problem recommend against encapsulating a ceiling because they are concerned that the weight of the layer of encapsulating material would cause the old material to loosen and drop from the ceiling.

The decision to remove the old material or enclose the ceiling is one that should be made by a certified asbestos abatement consultant. Abatement companies can be found in the Yellow Pages. Most abatement companies offer free estimates.

It’s important that you correct the asbestos problem, not only for your own health but in case you intend to sell the house; you can be sure the asbestos ceilings will become a negotiating item.

Pressure-Treated Wood Needs Staining

Q: I am building several outdoor projects with pressure-treated wood. I’ve been told that the wood should be stained. I was under the impression that pressure-treated wood would last in its natural state for years, just the way it comes from the lumber dealer.

A: Outdoor or pressure-treated lumber is treated with chemicals to resist decay and insect attack. This procedure permits the consumer and forest industry to make use of inferior grades of lumber, rather than increasing the demand for redwood, cedar and cypress. But, unlike these higher grades of timber, which are naturally decay- and insect-resistant, the lesser ones have a more pronounced grain and are more prone to splinter and crack. So, even though the wood is treated, it is best to apply a stain--or at least a water repellent--as soon as your project is dry enough to take a stain.

The first tip for working with pressure-treated lumber is to let it dry before using it. Other woods, including redwood and cedar, are dry when you buy them. But treated lumber is injected with massive amounts of chemicals and water. For wood that will be in contact with the ground, these liquids penetrate the wood completely.

If possible, handpick your own wood at the lumber yard. Select lumber that looks straight and true and is lighter and drier to the touch. These pieces have less water content and will be ready to use sooner. For very heavy lumber, understand that the extra weight you feel is fluid weight and will evaporate in time. Stack wet lumber on a flat surface such as a driveway or patio, use spacers between boards to let air circulate, and check the wood for weight and by touch for moisture. Pressure-treated lumber can need to sit for four or more weeks in 90-degree weather until it is dry enough to use without shrinking.

When the wood is dry, it might be too hard to nail. Pre-drill holes for nails to avoid splitting the lumber. Use construction adhesives and metal connectors to reduce the number of nails or screws needed. Use only galvanized nails or coated screws for assembly.

Apply stain or water repellent to the “down” side of the lumber before you nail it in place. Joists, braces and the underside of deck boards will be hard to reach and finish when you have nailed them in place.

Keep Slab Dry Under Wood Floor

Q: I would like to install a strip oak tongue-and-groove floor on top of an above-grade concrete slab. However, I’ve heard horror stories of costly wood floors buckling from moisture. How can I avoid problems caused by moisture that might accumulate in the area under the slab?

Answer: A hardwood floor can be installed on a concrete slab at or above grade. The Oak Flooring Institute recommends against below-grade installations.

Moisture is the chief culprit in hardwood floor buckling, so test the slab for dryness. Tape one square foot of clear polyethylene sheet to the slab, sealing its edges with plastic tape. If, after 24 hours, no clouding or moisture droplets have formed under it, the slab is dry enough to install a wood floor.

To prevent moisture from reaching the underside of the hardwood floor, place a vapor barrier of either building felt or polyethylene plastic over the slab before installation.

Condensation Plagues Metal-Roofed Porch

Q: I built a porch with a metal roof on it. We enclosed it using storm windows but have not installed heat. The problem is that in the summer with the windows open, condensation forms and runs off the inside of the roof. What is the best way to stop the condensation? Will installing plywood and shingles over the metal help?

A: To stop the condensation from developing, prevent the vapor in the porch air from contacting the cold metal roof. Putting plywood and shingles on top of the roof will not help. Instead, you should put insulation under the roof and cover the insulation with a vapor barrier.

With this installation, the vapor will not migrate beyond the vapor barrier. Also, because of the insulation, the vapor barrier will have a temperature that is above the dew point. Consequently, condensation will not develop. You can cover the insulation and vapor barrier with drywall or wood panels.

Patching Large Holes in Walls

Q: I recently installed a central heating system in my home. The old heaters, measuring 20 by 60 inches, are mounted back-to-back in the wall between rooms. Removing these units will leave a huge pass-through between rooms. I want to frame out the openings and repair the walls so the patch won’t be noticeable. Should I use lath and plaster, or should I try to make a flush patch with easier-to-handle wallboard?

A: If you want a perfectly smooth wall, you should cover the entire wall--from corner to corner--with wallboard. It’s very difficult to achieve perfection with a patch. Depending on how light strikes the wall, you will see ripple shadows at the patched joints.

But, if you intend to hang pictures on this wall or cover it with a textured paint or wallpaper, patching would be adequate. Because of the size of the opening, filling it with wallboard would be best.

Can Plastic Pipe Be Used to Repair Copper?

Q: I’m replacing some bad sections of copper water pipe. Can I use PVC pipe for the repairs?

A: Plastic water pipe can be joined to steel and copper pipe by means of plastic threaded adapters. Both male and female plastic adapters are available. One end of the plastic adapter is glued to the plastic pipe and the other threaded into a fitting or onto a pipe.

When joining plastic water pipe to existing metal piping, wrap the male threads with plastic pipe joint sealant tape. Because plastic female adapters can expand when threaded onto male threads, a better choice is to use a plastic male adapter threaded into an iron or copper female adapter or fitting.

To submit a question, write to Popular Mechanics, Reader Service Bureau, 224 W. 57th St., New York, NY 10019. The most interesting questions will be answered in a future column.