Ask The Experts

Roof Coverings

The shingles on my roof are only 10 years old and are already heavily cracked and worn looking. My roofer says that the shingles are defective. The manufacturer says that the installation is faulty. How can I get this resolved?

There is a good chance that they are both right, but we suspect that most of the responsibility lies with the manufacturer. The longevity of asphalt shingles can vary widely depending on the quality of the manufacturing process. In our experience all of the major shingle manufacturers are capable of occasionally producing defective shingles that age prematurely. You may notice examples of roofs with shingles in generally excellent condition, but with several shingles severely deteriorated. The visibly deteriorated shingles are clearly defective and could be easily replaced. A more serious common defect arose in recent years from unforeseen problems with the newer fiberglass based shingles. Expansion and shrinkage stresses in the fiberglass mats that form the basic structure of the shingle caused the shingles to tear apart. The cracks are usually fully through the shingle. This has resulted in thousands of prematurely failed shingle roofs. Another manufacturing defect occurred with imitation architectural grade shingles, where a double layer of grit is applied to simulate the laminated appearance of true architectural shingles. For reasons that are not clear to us, they tend to crack in the patches with two layers of grit, shortening the shingle life.

The defects that you describe are more likely to be due to manufacturing problems than the quality of the installation. However, if the attic space is poorly designed or inadequately ventilated, excess heat from the attic may accelerate the deterioration. This is often the reason cited by roofing manufacturer representatives to explain premature failures. Getting complete satisfaction from either the manufacturer or the installer is pretty unlikely after ten years. At this point your best option is probably to obtain an objective opinion from a licensed home inspector. Your inspector can assess the adequacy of the attic ventilation, apprise you of any imminent leakage issues, and determine the approximate remaining life of the roofing material. Then you can save up for the new roof when replacement becomes absolutely necessary.

Water seems to chronically drip behind the gutters on our new house. Our builder claims that the gutters are properly installed. What can we do to correct this problem?

Your builder is probably technically correct. The gutters are correctly installed but the drip edge is likely to have been installed too tight to the fascia. This results in a good appearance but is also likely to result in a slight lifting of the drip edge due to pressure against the fascia and curling of the water down the drop leg of the drip edge and down the fascia behind the well installed gutter.

The drop leg of the drip edge can be pulled out away from the fascia or a strip of flashing added behind the drop leg and into the gutter to prevent the water from slipping behind the gutter.

I have dark streaks on my five year old roof. What causes this, and how do I get rid of them?

The dark stains are caused by very hardy blue-green algae growing on your asphalt shingles. The stains are most apparent on white or light colored shingles. Algae are not terribly damaging from our experience, but may slightly shorten the life of the shingles. There is no doubt though that the effect is aesthetically unpleasing. The stains are likely to slowly get worse as the algae retain moisture, supporting more growth. The algae spores float in the air, looking for a good place to land, so if the algae grow elsewhere in the area, they are likely to end up growing on your roof. The only easy way to control the algae is with zinc. There are a few manufacturers of metal strips made primarily of zinc, designed specifically for this purpose. The zinc strips are intended to be installed on the shingles just below the peak of the roof. The metal strips are nailed below the shingle tabs and extend beyond the shingles along the bottom edge. As rain runs down the roof it picks up a small quantity of the metal which then washes over the algae, preventing further growth. This method is unlikely to get rid of all the algae that are already there. For that it may be necessary to wash the roof with a specially formulated chemical cleaner. The cleaner is normally applied with a garden type sprayer. The use of bleach is not recommended, because it is not particularly effective, may result in discoloration of the roof, and could harm shrubs or plantings around the house.

Zinc strips have the added benefit of controlling moss growth. The bright green moss usually grows under overhanging trees, due to nutrients dropping from the branches. Moss holds large amounts of moisture that accelerates shingle deterioration. The zinc strips may also control lichen growth, although the manufacturers make no claims regarding lichens. Lichens, which look like small, crusty, grayish splotches on the shingles, are very damaging. Since removing lichens also removes the grit on the shingles, exposing the unprotected felts below to damaging sun and water, a pro-active approach is best. Zinc products for control of algae are readily available, so, with a little effort, you can have a good looking roof again.

I am trying to determine if I need a new roof on my house, but I’m getting a wide range of opinions, from no life left to five years life. How can I determine who is right?

One way of looking at the life of the roof is to say that the shingles are okay until they leak. The problem is that you may not be aware of the leakage, (if it is low volume,) until major hidden damage has occurred. Asphalt roof shingles, whether the older organic type or the newer fiberglass type, have an expected life of roughly 20-30 years. But the actual life can vary tremendously, based on wind and sun exposure, roof pitch, heat build-up, and many other factors.

To complicate matters, most roofs leak before the shingles wear out. They leak because flashing details fail, because the valleys wear out, or because ice-dams cause backup under the shingles. (Flashings are installed where the roof shingles meet roof penetrations like chimneys, plumbing vents or walls. Valleys are the troughs formed when two roof slopes come together, concentrating the flow of water. And, ice- dams occur in winter at the eaves.) These conditions are normally repairable without replacing all the shingles.

There are three basic failure modes for roof shingles. Shingles are likely to need replacement if they are especially susceptible to wind damage, due to a defect or improper installation, if they are prematurely cracking, or if they are simply worn out. Simply being worn out is the most common reason for replacement. Wear is determined primarily by the degree of grit loss. The fine granular surface on shingles that provides their color also protects the asphalt from the sun and rain. If the grit is missing, the asphalt below will wear through within a few years. The loss of granular protection is especially important in the water courses, which are the spaces between the exposed shingles. Grit loss or minor curling at the exposed shingle tabs indicates an older roof with a few years life remaining, but significant grit loss in the water courses means that a new roof is due.

Assessing the life of shingles from the ground is not reliable. The shingles will need to be viewed up close to determine the degree of wearing. It might be helpful to you to ask the individuals who are evaluating your roof what criteria they are using to determine the remaining life.

I am having trouble with a roof leak that seems to happen only in winter, and is still happening even after I had new shingles installed. I’ve had the roofer back, but he can’t find the problem. Do you have any suggestions?

Diagnosing roof leaks can be extremely difficult, even when doing an onsite inspection. Using a hose to try to simulate the leak conditions can be helpful, but in your case, since the problem is winter related, such a test is unlikely to be beneficial. The fact that the problem seems to occur in cold weather suggests two likely related scenarios. You may need to analyze the specific circumstances under which the roof leaks to determine if either of these is correct.

During periods of extremely cold temperatures frost can build up at locations where warm humid air from the living space is escaping through a poorly sealed ceiling. A significant buildup of frost at a location on the underside of the roof decking can result in dripping water and stains when the weather briefly warms up. Inspecting the attic space directly above the leak for frost during a cold period, and sealing any possible cracks or gaps where warm air can escape, may prevent your problem. Frost may also build up in plumbing vent pipes, as well as bath, kitchen and clothes dryer ducts in the attic, and then leak into the ceiling.

The other possibility is that ice-damns are the source of the problem. Deep snow on the roof can form an insulating blanket that allows the heat that is lost to your attic to melt the layer of snow closest to the shingles. The resultant water builds up behind the ice at the bottom edge of the roof, backs up beneath the shingles, and flows down into the house. This would be likely to occur only when the snow is deep and the temperature is below freezing. Improving the attic ventilation and insulation is the best way to reduce the likelihood of this type of leakage. Removing the snow or installing electric heat tape at the eaves can also help prevent this leakage.

I have a twelve year old asphalt shingle roof, and I have had several shingles blow off. Is this the fault of the roofer or the manufacturer?

Modern asphalt shingle roofing commonly consists of fiberglass-based shingles, which are generally thinner and lighter than the older wood fiber-based shingles. They are therefore more likely to blow off if defective or poorly fastened.

There are several potential causes for the problem you are experiencing, so a thorough on-site professional evaluation by an unbiased inspector will probably be necessary, but we can enumerate some of the possibilities.

To compensate for the lighter weight shingles manufacturer’s applied dabs of an adhesive to the solid portion of the shingle to seal down the exposed shingle tabs. These can be too effective, causing the shingles to tear apart as they expand and contract with changes in temperature. The resultant pieces of shingle may then blow off. This is clearly a manufacturing defect, characterized by readily visible extended cracks fully through the shingles. The other potential manufacturing defect is that the adhesive is too weak, allowing the wind to lift and tear off the individual shingle tabs. This will be evident if you are able to get up on the roof and try to lift up the individual shingles with your hands. If the adhesive offers no resistance, apply caulk adhesive below any unsealed tabs. It is just as likely, however, that the shingles were improperly nailed. Most modern installations are done with a nail gun using compressed air. If the air is not properly set, many of the nail heads may blow right through the shingle, leaving the shingle unsecured. In some cases, roofers simply haven’t used the minimum number of nails specified by the manufacturer, or put them in the wrong locations. In other instances the fasteners may be too short to get a good grip, especially if there is more than one layer of shingles. Or the wood decking that the shingles are being applied to is deteriorated and not holding the fasteners very well. If the pieces of shingle being blown off are larger and include nail holes, the installation is probably the problem. Correction is likely to require a complete tear-off and replacement.

I have an original slate roof on my house. How do I know when it must be replaced, and what should I replace it with?

The glib answer to the first part of your question is to replace the roof when you don’t want to keep paying for the maintenance. The normal life for slate roofs in our area is at least 60-80 years. The limiting factor in the life of a slate roof is often the fasteners and flashings. These metal parts, usually copper, can deteriorate faster than the slates, resulting in leaks in valleys or around dormers and chimneys when the flashings wear out, or loose slates falling off the roof when the fasteners wear out. Replacing the metal flashings is a very expensive proposition, but may be worth it if the fasteners remain generally sound and the shingles have not shown excessive deterioration. Slate deterioration usually shows up as cracks, missing pieces, or heavy flaking, as the surface of the stone weathers. If the slate shingles are over 60 years old, you will probably have to establish an annual repair budget, and be on the lookout for cracked or missing shingles, or for any new leakage damage, to interior finishes or to the eaves areas. If money is no object, and you are tired of the maintenance, you might want to consider a whole new slate or tile roof. The aesthetic appeal of a slate roof is hard to beat. There is a new slate installation system called Nu-Lok, using horizontal metal battens for mounting the slates and vertically installed metal channels that lie under each butt joint between the slates. This method significantly reduces the amount of slate required and provides improved ventilation of the roof. But, even if a slate roof lasts a hundred years, it is still likely to cost quite a bit more per year than heavy weight asphalt shingle roof coverings lasting 25-30 years per application.

I need a new roof on my house. I believe that there are two layers on there now. Can I install a third layer, or would that be too much weight?

Three layers of shingles could result in more weight than the roof framing was designed to handle, but that isn’t the only potential problem. First, it is no longer acceptable to install more than two layers of shingles on a residential structure per the International Residential Code, recently adopted by New York State. Prior to this code localities varied between accepting two or three layers of shingles as the maximum. There are several other difficulties to bear in mind when contemplating installing more than one layer. It is important that the nails that are used to fasten the shingles be long enough to penetrate through the previous layers, and the wood roof sheathing. Often they are not, resulting in shingles blowing off in the wind. When added layers of shingles are installed, the flashings, (the metal pieces that tie the roof shingles to any protrusions such as chimneys) are not readily renewable. By the time you add a third layer, the original flashings are very old and are probably not in adequate condition, allowing potential leakage into the structure. Also, if the flashings are not renewed, there really isn’t much of anything to prevent water from entering between the earlier and later layers of shingles around chimneys and other breaks in the roof. You may have observed roofs that have streaks of heavily deteriorated shingles below a chimney or some other roof protrusion. This is caused by the deteriorating effects of chronic water seepage between the layers. Roofers combat this problem by applying plastic roofing cement around the old flashings at chimneys, plumbing vents, and sidewalls, but this is only a temporary fix. If the roof butts up against siding, such as at a dormer, it is likely that the shingles will be so thick that they essentially bury the bottom of the siding that is next to the shingles, causing chronic moisture and decay. Finally, multiple layers result in a lumpy roof. The shingles will not be able to lay down smoothly and the unevenness can result in accelerated deterioration. While tearing off the old shingles before adding new ones is a significant added expense, not to mention a big mess, it is almost always the wisest choice, especially if there are already two layers.

We are having problems with water leakage due to ice buildup. I’m wondering if a metal roof or architectural shingles would help?

Ice dams occur when heat from the home rises into the attic and melts the layer of snow closest to the roof shingles. This melt water, hidden under the insulating blanket of snow on the roof, flows down to the unheated eaves where the cold air causes the water to turn to ice. The ice builds up in a dam that causes the continuing flow of water to pond on the roof. The standing water easily backs up through the shingles where they overlap and flows into the overhang or the house walls.

If ice dams persist despite your best measures to cool the attic with more insulation and better ventilation, then the best solution is to provide some kind of continuous watertight membrane that will not allow the water to get through in the affected areas. There are many ways to accomplish this, but a different grade of shingles is not one of them. The water is still going to get through the layers. The most commonly used method in our area is to install a flexible self-sticking bitumen membrane along the eaves, just below the shingles. The material is readily available and comes in three foot wide rolls that are applied right to the roof deck, or to a lower layer of shingles, if the roof has multiple layers. This material provides an excellent seal, even around the shanks of the nails used to resecure the shingles. Other materials include metal roofing, often seen along the eaves of New England homes, roll roofing of various types, or rubber roofing. These all provide a continuous seal against water leakage.

Many people use heat tape along the eaves to melt the ice dams, but the heat tape is unreliable and often damages the shingles where attached. Using a roof rake to remove the insulating blanket of snow is very effective, but hard work, and sometimes the problem is out of reach. Whatever you do though, don’t go up on the roof with a hatchet to chop out the ice dams. You will likely destroy your shingles in the process, despite your best efforts to spare them. Try using rock salt to melt the ice after removing the snow.

We have a wager going whether gutter hangers should be installed on top of, or below, the roof shingles. We await your opinion.

It depends. If you have been reading our column for awhile you know that there isn’t likely to be a simple answer. Gutters are a popular topic, and for good reason. Every inspector knows the importance of roof gutters. Water is the number one enemy of homes, especially in our climate. Gutters prevent splash damage on the exterior and water entry into basements, or worse. But they are also a nuisance and require maintenance. One of the downsides is that they often don’t stay where we put them. The weight of snow and ice can easily bring them down if we don’t install them correctly. If you want to keep your gutters against the roof, they should be secured at least every two feet, and you should use galvanized screws rather than nails, if possible. The type of hanger and the location of attachment is going to vary depending on the type of eaves you have on your house and the condition of the wood. There are two basic types of hangers; those that mount to the fascia board and those that secure to the roof. Many gutters are attached to the fascia, the board that sits directly below the lower edge of the roof and behind the gutter. If this board is sound and well attached to the roof framing, this method works well and the fascia mount hangers will not be visible. There are two types of roof hangers. With the less expensive strap type, the thin strap can be easily secured below the shingles for a less obtrusive look and a good seal, but they are not as durable as rod and nut hangers and they are not adjustable. Rod and nut hangers have a much thicker arm that doesn’t allow the shingle to sit tight to the roof, presenting a poor appearance, if they are installed below the shingle. And, they require making holes in the shingles, allowing potential leakage, if installed through the face of the shingle. Neither method seems very desirable, but securing the hanger rods directly through the face of the shingles has our vote. As long as the fasteners are in place and tight, leakage is unlikely, and a dab of clear silicone caulk at each screw can provide a little insurance. Whatever method you use, gutters are worth the trouble if you care about your home.