Q–I have a nearly flat roof that is driving me crazy. The asphalt, rolled roofing products I use only seem to last five years before they begin to leak. What other alternatives do I have? There seem to be hundreds of commercial buildings near me that have similar roofs. When I go into these businesses during a rainstorm, I don’t see leaks. Can I put a similar roof on my house?
A–Many other homeowners share your frustration. There are literally thousands of houses in my own city that have low-pitched or flat roofs. Traditional asphalt roofing materials are susceptible to failure because of the method of application and material quality issues. The roofing industry has known about this problem for many years.
During the 1950s and 1960s, new membrane roofing materials started to appear that solved many of the asphalt roofing problems.
Traditional asphalt shingle systems do not work on flat or nearly flat roofs. Shingles work in conjunction with gravity to keep the inside of your house dry. Water runs down the roof and over the top of shingles. Strong wind and ice dams can defeat these gravity-based systems.
Flat roofs and extremely low slope roofs need a gravity-proof roofing solution. It appears that the new single-ply membrane roofing materials may be just the thing. The commercial buildings you mention very likely are covered with one of the many different types of single-ply membrane roofs.
The new single-ply membranes are actually synthetic compounds that can be mechanically fastened or glued down to your roof deck. Some of the materials are synthetic rubbers while others are special PVC plastics. There are several other types as well. All seem to have very respectable life spans. Warranties of 20 or more years are not uncommon.
One distinct advantage of these new membranes is the possibility of seam elimination. Seams in the traditional asphalt systems were usually the first place water might enter. If your low-slope roof has no chimney or plumbing/heating vent pipe penetrations, it is possible to cover the roof with one giant piece of roofing material. This is like “shrink-wrapping” your roof. Believe it or not, some of the materials come in 50-foot widths.
Narrower pieces are often used for residential work. They are easier to handle and there are special adhesives, solvents and tapes that assure leak-free performance at the seams.
These membrane roofing systems also permit you to upgrade your house insulation. You can install high-performance insulation on the roof deck before the membranes are applied. Often a thin, half-inch-thick fiberboard sheet is placed on the insulation or roof deck before the single-ply membrane is attached. The fiberboard helps to protect the underside of the membrane from defects in the roofing deck.
The cost of the single-ply membranes is not too bad. A typical job, where no removal of old roofing is required, might cost $250 to $400 per square. (One square of roofing equals 100 square feet of roofing area.) This cost will vary depending upon how many obstacles are in or near your roof, whether you decide to upgrade your insulation and what overall quality of roofing membrane you choose to use. For sake of comparison, a standard shingle roof on a house might cost $60 to $80 per square.
If you happen to win the lottery, there is another time-tested roofing material you can use that works well on flat or nearly flat roofs. You can install a flat, locked, fully soldered, seamed tin or copper roof. These roofs are extremely labor intensive to install. The use of hidden clips allows these roofs to float on the wood deck below. Copper roofs of this type will cost you about $2,000 per square. By using tin, you can cut this cost to $1,600 per square. A tin roof will require periodic painting. But heck, if you win the lottery, who’s counting?
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
For a list of manufacturers of single-ply membrane roofs, descriptions of different membranes, and other tips on locating leaks in flat roofs, please send $2.00 and your name and address to Tim Carter at the above address. Ask for Builder Bulletin No. 195.
For a list of past Builder Bulletins and a wide variety of individual job bid sheets, send a business-size, stamped, self-addressed envelope to the same address.
Ask the Contractor can also be accessed via the Internet at http://www.chicago.tribune.com/homes/articles/askcon.
