Answers to Your Roofing Questions Answers to Your Roofing Questions

Q. We are currently having plans made up for an extension to our house the kitchen and spare room. We are unsure whether to go for a flat roof or a tiled roof. Which is the preferred option, i.e., longer lasting?

A. A tile roof will last longer and have less maintenance. You have several options with a flat roof, and depending on the company that installs it and the climate you are in, it can last for years, or be a perpetual headache. Single ply membranes (like a rubber roof) typically last 10 years or so before they need maintenance. What happens is the rubber will shrink, creating tears at seams, or at the termination strip around your roof perimeter.

Depending on the design, a properly installed hot-mop roof (another type of flat roof system) will last 15-25 years. Both these designs call for rock aggregate over the top.

Q. I have a rubber roof, and one of the seams has opened, causing a leak in the roof. What sealant/caulk do I use to fix this?

A. Pull back the seam as far as you can to see the dirty area, until you start to feel resistance. Wipe off any dirt, etc. Obtain a 1 gallon can of seam cleaner/primer from your local Roofing Materials Wholesaler (look in the yellow pages). Pick up 1 gallon of seam glue and pick up a tube of EPDM caulking. Clean off both of the sides you want to glue together with the cleaner/primer. After it's "set up" and tacky (a couple of minutes), apply the glue to both sides. After it's "set up" and tacky (this will take several minutes), push the two sides together, working the air bubbles out. Then apply the rubber caulking to the finished seam.

Q. We are installing about seven squares of shingles on an outbuilding. The old shingles were torn off and the felt/ice dam materials were installed during dry weather. We also applied shingles to about 3/4 of one side before the rain started. It wasn't a lot - just enough to get things wet. But, the forecast calls for off and on rain for the next week, and it's supposed to remain mostly cloudy for a while, and we don't have time to wait for ideal conditions. Will applying black shingles over damp tarpaper cause a problem?

A. It's recommended that you wait for the felt to dry, but it's not uncommon at all to go ahead and roof. It's done all the time. You shouldn't have a problem.

Q. I'm thinking of changing from white/gray asphalt shingles to a light brown. Someone told me the brown would absorb more heat and raise my cost of air conditioning. Is there a rating for heat absorbency?

A. Actually, it's a bit more complex than that. It also depends on how well your roof is vented. Plus darker shingles help keep the house warmer in the winter. You need to weigh all the needs, not focus on a single season. The white/gray are called frost, the light tan are usually called autumn. The absorbency rate between the two is not very much.

Q. I noticed a bulge about 2 feet long and 6 to 8 inches wide in my roof. Upon going onto the roof I have found that there is not evidence of anything hitting the roof, and the shingles are all intact, but it feels like the bottom of one of the pieces of plywood sheeting has buckled upward about 2 inches.

The house is only two years old, and my wife works for the homebuilder, so getting the roofers to repair it cheap or free is not a problem. But I was just curious if anyone had any idea what would cause this. While I was up there I inspected the rest of the roof and all seems fine.


A. How about the possibility that the decking was never completely nailed off during original construction? One problem with new construction is that a lot of the roofs are only warranted for a year In fact, even the smallest area of unnailed decking has a tendency to "poof" and buckle up if allowed to do so.

Q. We live in an adobe home. The home has a flat roof that leaks. The entire area of the perimeter has parapet walls about 4 ft. high with scuppers to allow drainage from the roof. There is insufficient slope to the roof. If we have crickets built to direct the water toward the scuppers, what is the best roofing material? We have modified bitumen currently but we experience leaks. What about metal? We live in the foothills of the Rockies and get snow and hail. If a metal roof were installed, what kind would be best?

A. You need to get positive slope-to-drain. Tapered insulation is probably better than wood crickets. Check the tie-off, if there is one. Metal is probably not an option. Low-sloped metal is designed for large industrial type buildings, and is difficult and expensive on small jobs. In addition, parapet walls are almost impossible to deal with in low-sloped metal. Tapered insulation is a "system" which will include a combination of rigid dimensionally uniform "boards" and rigid boards, which are tapered. These boards are laid down in such a way as to provide a continuous slope, providing positive drainage towards the area you want it to drain to. They would be attached to the deck with special screws and wide metal plates (like washers). There will be a minimum slope required by your local building code authority. Where I am, it ranges from 1/8-1/4 in. fall per ft (depending on jurisdiction). The steeper the pitch desired, the more it costs due to the simple fact it takes more insulation.

There are a number of insulation materials used in making these boards. One preferred type would be Isocyanurate (known as "Iso board"). It's a type of lightweight foam, which happens to have excellent R-values. Although it can be easily dented, it is walk-able once it covers the roof. A better thing to do would be to install 1/2-CDX plywood over the insulation prior to roofing it. Besides providing a more rigid/solid surface, this would incorporate the insulation in a more permanent fashion. This is my opinion, but I tend to think about "down the road." If and when the roof needs to be stripped and replaced, the insulation might very well suffer from the stripping and need to be repaired, sections replaced, etc. I've found that this rigid insulation tends to degrade some as it is, over the years. Isolating it with the plywood would tend to protect it. But, it's all about money and a homeowner's needs and interests. Bottom line, as in all roofing applications, this tapered insulation needs to be installed according to manufacturer's specs. Frequently this system is installed with insufficient screws, allowing boards to buckle, which also happens to affect the roof covering.

Q. I have noticed two rafter tails near the valley of my roof starting to deteriorate from water damage. With a new roof, the source of the damage is taken care of, but what is the best way to take care of the rafter tails now?

A. It depends how bad the "deterioration" is. If it's only on the surface, sand down to solid wood with 60-grit sandpaper, then prime and paint. If it's bad, and you just want to improve the appearance, someone with a metal break could cover them with aluminum trim coil.

Q. What is G.A.F rubber roof? How it last long? Is it good for flat roofs? How do you maintain it?

A. GAF rubber roofs are rubber roofs made by the GAF corp. They have 14 types of Ruberoid Roofs, 6 types of Ruberoid Heat Weld Roofs, 2 Ruberoid Granular roofs, and 6 Everguard Rubber roofs. You have a lot to choose from. You need to have the correct roof for your situation. It is not easy to install. Most of the time, it must be installed by pros. It must be double glued, and the black glue comes in 5-gallon pails. The rubber is terribly heavy. You must be sure your roof can hold it, and the list goes on.

Q. I just had a garage built, and want to install the roof underlayment. Once installed, will it matter if it rains on this material? Do I need to install the shingles right away?

A. Either way, it won't matter so long as you plan on installing shingles in the very near future. If you're using standard tar paper and it gets rained on, you will notice it wants to buckle/wrinkle, which can be a pain to deal with. So if you're planning on shingling within a week, I wouldn't even bother installing tar paper until that time. A big misconception is that rain will hurt roof sheeting. Over a period it will - just as it would with wall sheeting - but many newly built homes are left sitting for a few weeks with exposed sheeting and deal with all the elements with no ill effects. Just get it shingled as soon as you can.

Q. My flashing around my chimney was rusting and left a rust stain on my roof. How do I remove the stain without damaging the shingles?

A. Obscure the discoloration with sparsely applied spray paint.

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