Frequently Asked Questions

There are several clues, and the biggest one is age. If your roof is more than 20 years old, there's a good chance it's due for replacement. But younger roofs can fail too, so it's a good idea to inspect a roof at least once a year. Don't use a ladder, though. Binoculars are easier and a lot safer, and you can spot most problems from the ground.

Here's what to look for: numerous shingles that are lifting up, cracked or missing, with curled edges, or with smooth dark areas, which indicate that the protective granules have worn off. Also, go into the attic on a sunny day and, with the lights off, check the underside of the chimney and the stack vent. If you see little pinhole spots of light, the flashing is shot—another indication that the roofing might not be in good shape.

While you're in the attic, scan the underside of the roof for any new signs of water staining since the last inspection, as well as any soft or moist spots, which tend to show up after a heavy rain. If these problems are widespread, it's a sure sign that you need to call a roofer.

It's difficult to say. On one hand, a steep roof is less likely to collect leaves and other debris that hold moisture against the shingles and invite the growth of moss and algae. On the other hand, that same roof in an unshaded area facing due south will take the full brunt of the sun, which is hard on any roof.

Actually, factors other than pitch have a greater effect on shingle durability. The side facing your worst weather typically fares worse than the leeward side. Likewise, a roof system that isn't vented properly and allows heat to build up beneath the roofing has a shorter life than one that is vented.

First, your roofers should lay down an ice and water shield over the entire roof. Made of polyethylene and rubberized asphalt, this membrane prevents water that has slipped under shingles from penetrating to ceilings below. The valleys should then be covered with metal flashing or weaving.

Flashing is just material—usually aluminum or galvanized steel—that's used over joints in roof and wall construction to prevent water seeping in and causing damage. Depending on the style of your house's roof, you probably have it in the valleys, around the chimney and pipes, and around any dormer windows or skylights. Most damage shows up either in flashing that's deteriorating due to weathering and oxidizing, or in flashing that has come loose.

The dark streaks are a type of algae that lives off the minerals in some types of roof shingles. Algae thrives in moisture, so it's seen most often on shaded or north-­facing roof slopes that don't get a lot of direct sun.

While it's true that algae doesn't damage roofing, it sure looks bad. To get rid of it, use a pump sprayer to wet down the roof with a mix of one part bleach to two parts water. Bleach will damage foundation plantings, so rinse them well with fresh water before you start and after you're done.

Then scrub the surface gently with a soft window-washing brush mounted on a telescoping extension pole. Don't use a pressure washer, which could damage the shingles. Also, do this work from the safety of a ladder or from the ground, not by climbing on the roof.

To stop the algae from returning, mount zinc or copper strips near the roof ridge. Then, every time it rains, the water that washes over the strips' exposed edges will pick up ions from the metal and inhibit the algae from regaining a foothold. And when it's time for a new roof, look for shingles with algae-resistant granules and the best warranty you can find.

Basically, what you want to do is cover the damage with a woven plastic tarp that is held in place with 1x3 wood strips. Here's how I do it. First I roll one end at least twice around a long 1x3, then screw it to the undamaged side of the roof. The 1x3 "roll" should be against the roof so it won't collect water and debris. The rest of the tarp goes over the ridge and down the other side of the roof several feet beyond the damage.

Then I roll the opposite end of the tarp around another 1x3 and screw it to the roof sheathing, roll side down. Now it's just a matter of using more 1x3s and screws to hold down the tarp's sides. They don't have to be rolled in the tarp. A "blue roof" isn't pretty, I'll admit, but it will keep the weather out until someone can repair the damage.

Having said that, this type of emergency repair is best left to someone who has the equipment and skill to do it safely. Roofs are treacherous, particularly when wet, and tarps are slippery even when dry. You don't want to be wrestling with one in high winds, either. Better to submit a claim for property insurance than to have your family submit a claim for life insurance.

Yes, you need to strip the shingles. A single layer looks better, lasts longer, and won't put any unnecessary extra weight on the roof.

As to which shingles to use, the longer the warranty, the heavier the shingle and the greater the cost. You want to look for the best warranty you can afford.

What's happening is that warm, moist air from inside your house is seeping into the attic and the moisture is condensing and freezing on the cold steel. And yes, you should do something to stop the seepage because it can reduce the effectiveness of your insulation and encourage mold growth.

There are three steps to solving this problem. First, seal off any openings for air to leak into the attic. Maybe a bathroom fan isn't venting outside or the pull-down attic stairway needs weatherstripping or the light-fixture boxes aren't sealed. A home-energy specialist with a thermographic imaging device can pinpoint many small leaks you can't see.

Second, try reducing moisture levels in the house by turning on exhaust fans when bathing and vent fans when cooking.

Third, make sure the attic is well ventilated so that any moist air that gets past your defenses has a way to escape. Soffit and ridge vents are more effective ventilators than fans, and they don't use any energy. If you already have these vents, make sure they aren't being blocked by insulation.

It's always tricky to pinpoint the exact location of a leak. It may appear to originate in one area, but water is sneaky and moves in unexpected paths. So before you jump into this job, try to determine where the leak is coming from. If the porch has a finished ceiling, for example, remove a few boards and check the underside of the roof sheathing for water stains—they may help pinpoint the leak's location. In the case of a low-pitched roof, you may have no alternative but to remove all the roofing just to track down the problem.

Chances are, the leakage is probably due to the flashing, not the roofing material itself. Damaged, corroded, or improperly installed flashing is a common problem at this location (and a lot of other locations, too). If the roofing material is in good condition, you may have to remove an area of siding as well as some of the roofing to replace any damaged flashing. (Generally, the only reason to remove all of the roofing would be if it's nearing the end of its useful life anyway.) A capable roofing contractor should be able to make this repair for you.