Caulking may help gaps in roof

Editor’s note: Henri de Marne is on vacation this week. These letters originally appeared in the column in 2011.

Q. I am an elderly widow who needs roof repairs. Light is showing in around two chimneys, and I need several slates replaced. Two roofers claim they fixed the problem, but my neighbor checked and said that the light is still showing through and that this is not normal, since rain can get inside and cause damage. They said I do not need flashing.

What can be done to fix this problem?

A. If your neighbor got in your attic and could see daylight around the chimneys, he or she is right in saying that wind can blow rain inside the roof.

The roofers may be referring to the combination of step and counter flashing when they said that it is OK. But if the various segments of the counter flashing are not tight to the sides of the chimney, which I assume to be bricks, leakage can occur.

Often, strong winds can cause the various legs of the commonly used lead counter flashing to open up. In such a case, the solution is to caulk the leading edge of each piece of the counter flashing to the one below it with polyurethane caulking. Don’t accept plain silicone, as it has a tendency to separate from most surfaces over time, especially under moist conditions, and is prone to mildew.

Q. I am planning on installing new rain gutters on a customer’s home. The end result is to have the gutters painted white. What steps and products should we follow and use to prevent the new paint from peeling on the new galvanized surface?

A. An old-time method is to wash the metal with white vinegar. A more modern way is to go to a paint or hardware store and buy a primer that does the same thing. GalvaGrip is one such product that should work well as a degreaser.

Q. We have recently had pressure-treated porch floor decking installed and have been getting conflicting advice on when and what to use for treatment. Could you advise us?

A. Today’s advice is to coat pressure-treated wood with a product specifically made for such wood as soon as possible after installation. You no longer have to wait a minimum of six months to let the wood dry. Wolman makes coatings for that purpose. There are others, but be sure it is the right product to apply right after installation. Other coatings, including paint, are doomed to failure.

Q. I have mold or mildew growing on the exterior of my house. We bought the house new four years ago. The house is clapboard painted white. The paint has also blistered in many spots. I have tried to use a power washer on the mildew and mold. It cleans off most of the black; however, some black staining remains embedded in the paint. Is there anything I can do to remove this? Is it harmful to leave the mildew alone until I am able to have the house painted? Is it OK to paint over existing paint that is stained by the mildew?

A. The pressure washing removed airborne dirt and mildew spores that attached themselves to the painted surfaces. The remaining stains are mildew spores that were on the siding before it was painted and were not cleaned off.

I think your problems stem from the fact that the house was not painted very shortly after the siding and exterior trim were put on. Mildew spores, always in the air, were deposited on the bare wood and were not removed prior to painting.

Unfortunately, a common mistake builders make is to wait too long to prime and paint the wood. In some cases, many months go by, particularly if the house was built when the weather was too cold to paint.

Good practice dictates that all wood be treated with a primer or a wood preservative on all sides before installation. When this is done, problems like yours are unlikely to develop as long as the primed surfaces are pressure washed and cleaned before applying the finish coats.

Blistering paint is also caused by contaminated wood to which paint cannot adhere because there were too many dead fibers, or the surface was too wet if acrylic paint was used, or not thoroughly dry if an alkyd paint was applied.

Leaving the mildew until you are ready to paint again will not cause a problem, except that it will get worse. Try to wash it off with a bleach solution or OXY-Boost by Pacific Sands. You can buy it online at www.ecogeeks.com. If you paint over mildewed siding, the mildew will come through again.

From your description, it looks like you will have to remove all dubious paint, power wash the surfaces and prime and paint them when they are dry.

Q. Someone on TV the other day talked about using roof tape on all the deck seams as an extra precaution against leaks. This would be underneath all the normal underlayment. Would you recommend this? My contractor says it is not necessary.

A. TV presenters have to have something different to say to keep their programs interesting and going. Most of these programs are really entertainment and are of limited use for viewers.

Your contractor is correct. If he or she installs an ice and water protective membrane at all eaves, valleys and roof penetrations, and reinforced felt elsewhere on the deck, there is no reason to go to that extra expense. There is no harm in taping the deck joints, but it’s like wearing a belt and suspenders, and still holding your pants.

Q. I’ve attached pictures of water damage done to the wall of our garage from cracks in the exposed cement porch, which is the roof of the garage. What would you recommend to repair both the cement on the porch and the block? As you can see from the pictures, we tried cement to repair the face of the block. Do you think we need to replace the block, and if so, do you know of any sources? This is the only section with damage.

A. It looks like you have caulked cracks on the concrete porch floor with silicone, which is unlikely to last when exposed to moisture for any length of time. Check to see if the caulk is peeling at the edges. If and when the caulk fails, peel it off, clean the cracks thoroughly and seal them using polyurethane caulking. You should also consider cleaning the concrete and sealing it with a masonry sealer.

The damage to the block foundation of the garage looks as if it was caused by seepage from the concrete porch floor that wet the inner core of the blocks and caused spalling in freezing weather.

Not enough of the blocks have been seriously damaged to present a structural risk to your garage, as long as you seal the porch floor and repair the cracks to stop the leakage. A competent mason can easily repair these blocks and attempt to re-create the textured look.

Q. My 15-year-old home in southwest Pennsylvania seems to have high humidity levels year-round. When it was built, we used the most energy-efficient methods we could afford: 10-inch block foundation with vapor barrier and 2-inch foam on the exterior; 2-by-6-inch exterior wall studs with R-19 fiberglass and 1-inch (R-5) foam all wrapped with Tyvek; Andersen windows; and a brick veneer. The basement floor has a vapor barrier, and the walls have been Drylok-ed.

We are using a 90-percent-plus efficient gas forced-air furnace with central air. The dryer vents outside, as do all the bathroom exhaust fans. Currently the humidity level is about 65 percent. We have tried a stand-alone 50-pint dehumidifier in the basement, and it runs almost constantly.

I always hear of adding a humidifier to the furnace for the heating season. I’m considering adding a dehumidifier instead to get the humidity down.

A. If you had the windows open during a good part of the summer, it would not be unusual to have the level of relative humidity (RH) you experience. But if you used the air conditioning throughout the summer, the relative humidity should have come down by now.

Because you experience a high RH level year-round, and because you have a tight house with an efficient furnace, you should look at the possible sources of such a high reading. Do family members take very long showers? Do you keep the bathroom fans on long enough after showering? How many of you live in the house, and how big is it? Do you have a lot of water-loving plants? Do you use a wood stove and store firewood in the basement?

How many pets do you have? Do you dry laundry on racks or always use the dryer?

Have you checked the grade around the house to make sure it slopes away from the foundation? Do the driveway, patio, walks, etc., lead water toward the house? Are downspouts discharging water onto splash blocks and onto a grade that slopes away from the house?

You mention having applied Drylok to the inside of the basement walls. Unless you know your foundation is properly backfilled so that no water can put pressure on the walls, it is possible that the block cores are filled with water, which would cause the excessive moisture.

It sounds like you may need an air-to-air heat exchanger.

Ÿ Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via email at henridemarne@gmavt.net.

© 2013, United Feature Syndicate Inc.