Do It Yourself: The benefits of stripping old shingles

Q. I want to get new asphalt shingles on my roof this spring. I’ve always understood that I can have new shingles installed over one layer of old shingles, which is what I have, but the contractor I like wants to remove the old shingles down to the sheathing. That would cost a lot more and I wonder if he is just trying to make some extra money. What do you think?

A. The contractor is giving you good advice. Although it is possible to install new asphalt shingles over a single layer of old ones, there are a number of advantages to stripping the roof to the sheathing. If the old shingles are stripped, the contractor will be able to inspect the sheathing and flashing for deterioration and defects.

The new shingles will probably last a lot longer if the roof is stripped, since heat generated by the underlying layer can cause early deterioration.

You might also discover that the manufacturer’s warranty will not cover your new shingles if they are installed over an old layer; ask your contractor for a written copy of the warranty so you can check this out.

Finally, if the old shingles are curled and swollen, as some asphalt shingles are when they age, the new shingles might not lay flat and have the best appearance.

If you live in a cold-climate area where ice dams are a problem, it also pays to install a special membrane above the gutter area to protect against roof leaks caused by water backing up under shingles.

You’ll save money in the short run if you roof over the existing shingles, but if you plan to live in the house for a long time, stripping the roof and paying the extra cost is probably the best option.

You can learn a lot about asphalt shingles at www.nrca.net, the Internet site of the National Roofing Contractors Association. Click on Consumers at the top of the page. The articles include a roof checkup guide for homeowners.

Q. The finish on my bathroom cabinets is chipping and peeling in places. The cabinets appear to be made of some kind of pressed wood, not solid wood. Can they be fixed and painted or is replacement the best bet?

A. Your cabinets, like most of the bathroom cabinets sold at home centers these days, are very probably made of particleboard, which is ground-up wood pressed and glued into the shape of boards or panels. The cabinets are usually finished with a thin coat of plastic called melamine. Much of the inexpensive furniture sold today is made of this material.

The problem is that particleboard does not hold up well in moist surroundings, which is the case in many bathrooms. In fact, the deterioration of the cabinets might be a signal that your bathroom needs better venting. If you don’t have an exhaust fan in the bathroom, you should consider installing one. If you already have a fan, check to make sure it is properly vented with a pipe to the outside, and that the pipe is not clogged.

Extreme moisture in bathrooms (or other rooms) can cause many problems, including mold and mildew, paint failure condensation on cold surfaces, and more. And if water gets into the particleboard, it can cause swelling and chipping or peeling of the plastic surface. Sometimes not all sides or edges of particleboard furniture are covered with the plastic, which aggravates the problem of water absorption.

Melamine-finished particleboard can be painted if it is in good condition, but if it has started to deteriorate it is very difficult to get an attractive paint finish. Any peeling or swollen areas have to be sanded smooth, and this exposes more particleboard, which doesn’t take paint well.

Replacement is usually the best option, but if the cabinets are an unusual size and replacements can’t be found, it might be possible to have them resurfaced with plastic laminate by a cabinet-renovation service.

When cabinets or furniture sit on a floor and only an inch or so swells because floor-cleaning water has been absorbed, the damaged area can often be smoothed and covered with painted baseboard molding.