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posted: 7/28/2013 12:21 AM

Locating roof leak's source may take some detective work

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Q. I have a perplexing problem. I have a flat roof on a house built in 1975. The previous owners had a foam roof installed shortly before I purchased the home in 1997. I had the roof coated within a year of moving in.

A few years ago, I had the master bedroom carpet replaced (this is on the second floor next to an outside wall) and noticed an area in the closet where water had evidently leaked in; as a matter of fact, it was still damp. Then, the following winter when the snow began to melt, water began leaking through the ceiling of the family room near where the bedroom closet was located. However, the family room is a remodeled porch that is on the first floor, but shares the wall with the bedroom closet (the original outside wall that is now the family room's inside wall).

The leak begins to drip through the ceiling about three feet from the wall and always in the same place. There is an asphalt-shingled roof above the family room and I had that roof replaced around six years ago. The side of the house where the leak occurs is facing east. We can have heavy rain with strong winds and no leak -- it leaks only when the snow melts. I had the flat roof recoated again last autumn and repaired the ceiling in the family room. However, when the winter snow began to melt, the leak reappeared. I have had several roofers look at the problem and, to date, no answers.

Do you have any idea how I might find this leak? The area between the family room ceiling and roof is not accessible.

A. Thank you for sending the photos; it is helpful in understanding the layout. From your description of the location of the leak and when it happens, my sense is that an ice dam forms on either the flat roof (which may be why the previous owners had it foamed) or the bedroom roof. I am assuming the flat roof received a sprayed foam coating since you mention having had the foam recoated; a rigid foam added to the original roof would have been covered with a rubber roof.

If an ice dam is still forming on the flat roof in spite of the foamed insulation, it prevents melting snow from getting into the gutter, or the gutter may freeze, causing a water backup into the roof structure. It is also possible that the flashing at the joint of the flat roof and the slanted bedroom roof to the left does not go high enough behind the shingles. In that case, water can creep up the wall and get behind the flashing.

It also looks from the photos as if there are flat roofs over both the mansard roofs over the bedroom and the other room to the right of the photos. There could be a separation or tear in the membrane to the right of the bedroom roof where it meets the mansard roof. An ice dam on that roof -- perhaps caused by the heat from the metal chimney causing the snow to melt -- may be responsible.

This is all conjecture, and it is unfortunate that no roofer has been able to determine the point of entry. If investigation of my suspicions proves not to be correct, you may want to have an engineer investigate.

Q. Some time ago, we painted the basement floor. For the last couple of years, the floor is bubbling and the paint is peeling. What do I do to prepare the floor before painting it? What product should I use?

A. I assume you mean that only the paint is bubbling and not the concrete itself -- which would be a far more serious problem.

It is difficult to paint a concrete slab. Concrete is not waterproof, so moisture permeating from the subsurface will lift any paint off the slab unless the ground below it is thoroughly dry or a very effective vapor barrier was installed and the concrete was allowed to thoroughly cure before any paint was applied.

If you want to put a coating on concrete, stain is the only way to go.

Q. I own a small cabin in southern Vermont with a cinder-block foundation. The English basement is dry and includes an efficiency apartment. I would like to apply some form of protection to the exterior aboveground cinder-block foundation, either primer, paint or some "Thoroseal" type product. Any insulation properties would be an added plus, so long as it doesn't turn into a carpenter ant highway.

The cabin wood siding has been spray-coated for 50 years with creosote or, more recently, a linseed-oil-based wood preservative. This has left very heavy splatter on the cinder-block foundation below, which would be pretty impossible to remove. Aesthetics are less of an issue than that of providing a good, lasting protective coating. What product or sequence of products would you recommend?

A. Considering the creosote and/or linseed oil stains on the blocks, it is best to use a cementitious coating, such as one of the Thoroseal products. Check its website ( and select the product you feel is best suited for your use, keeping in mind that these products are not decorative.

Any foam insulation you add to the exterior of the blocks may be susceptible to carpenter ant damage.

Q. Our house is 2 years old. The interior walls are unpainted, textured plaster, and we want to paint them. Will a latex paint that contains its own primer (Behr) cover in one coat? Or should we use a separate primer coat? If so, oil-based or latex? Second, what do you think of the foam rollers for textured walls?

A. On bare plaster, you should use an oil-based primer followed by whatever finish paint you choose. Rollers make painting go so much faster, but you will still need a paintbrush for corners, etc. On textured plaster, it is best to use -inch-nap rollers. Flat surfaces only need - to 38-inch rollers.

Q. My husband and I are at our wits' end. We have a raised ranch built in 1969 with a downward-sloping drive. The main part of the house sits a half-story above grade. Immediately inside the garage door to the lower level of the house is a cold air return, and immediately next to that is the furnace/hot water heater closet. Next to that is a laundry room with an original slide window that sits at ground level under the deck. The concrete garage floor has never been sealed.

Our problem is dust. I should say DUST, because I have never in my 40-plus years of housekeeping in houses of various ages, styles and geographical locations had such a problem. It is a fine, grimy, almost oily dust that gets into drawers, cabinets, closets, anything and everything, in mass quantities. It causes cobwebs of monumental quantity. The upstairs has typical forced-air heating. The lower level depends on add-on heat -- and it does not seem to have the same dust problem.

Before we start a never-ending process of having the ducts cleaned, can you offer any insight on where this grimy dust is coming from? There is no dirt immediately outside the garage door. The windows are all original and some do not fit too well any more. Could they be the source? We live on a quiet, paved suburban street. Please help. We are desperate to find an answer to this.

A. I am not sure what is causing the dust to feel grimy, except that it may be due to road dirt, tire wear, etc., but I am not too surprised at what is causing your problem.

A garage is always dusty, be it dust blowing under the garage door or brought in from the streets by your cars. The cold air return in the garage is most likely the source of the intake because the heater's fan is stirring up the air. I wonder why this cold air return was put there; it does not make any sense since the furnace serves only the upstairs. It should have been installed upstairs, and you may be able to have this done by an experienced HVAC contractor.

Suburban environments can be dusty; many cars traveling the streets, lawn mowing and other garden activities combined with 1969 vintage windows that are not tight by today's standards can also be a source of dust penetration.

You may want to consider having an electronic filter installed in addition to moving the cold air return upstairs.

• 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

2012, United Feature Syndicate Inc.

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