Q&A / 

Flat Roof Leaks – Try the Newer Rubber Roofs!

DEAR TIM: I have a nearly flat roof that is driving me crazy. The asphalt rolled roofing products I use only seem to last 5 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? Mark G., Defiance, OH

DEAR MARK: Many 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 1950's and 1960's, 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 these new membranes offer 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. It is like "shrink-wrapping" your roof! Believe it or not, some of the materials come in 50 foot widths.

Smaller width 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 insulations on the roof deck before the membranes are applied. Often a thin one half inch thick fiberboard sheet is placed on the insulation or roof deck before the single ply membrane is attached. The fiber board helps to protect the underside of the membrane from defects in the roofing deck.


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The cost of the single ply membranes is not too bad. A typical job that requires no removal of old roofing might cost between $250 - 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 the overall quality of the roofing membrane you choose to use. For sake of comparison, a standard shingle roof on a house might cost between $60 - 80 per square.

If you happen to play the lottery there is another time tested roofing material 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 approximately $2,000 for each square. You can cut this cost to $1,600 if you use tin. A tin roof will require periodic painting. But heck, if you win the lottery, who's counting!

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4 Responses to Flat Roof Leaks – Try the Newer Rubber Roofs!

    • Kathy, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

  1. 1) Can you use ice and water shield with a rubber roof system ( for a low slope roof).

    2) Can you use BOTH a thin layer of 1/2 inch fiber board on the sheathing ( decking?) to improve insulation AND ice and water shield with a rubber roof system for a low slope roof?

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