High & Dry: What Homeowners Need to Know About Roofs, Part 2
In last month’s Inspection Connection, we discussed roofing components, including the concept of roof incline and the five major foes of roofs. In this Newsletter, we’ll discuss roofing materials, leaks, maintenance, ventilation and safety concerns.
Types of Roofing Materials
Choices in roofing materials have expanded dramatically in the past five years. The type of roof on your house depends a lot on where you live, what is popular and what builders and homeowners have found that works best. It usually takes a decade or more for new products to prove themselves as worthy or unworthy.
In terms of sloped roofs, asphalt shingles are still the most popular product and comprise more than 70% of all residential roofs. These shingles are durable, reasonably-priced, easily installed and average 15-20 years life expectancy.
Asphalt multi-thickness shingles are heavier and will last longer than regular asphalt shingles, as will asphalt interlocking shingles, a product that has proven its value in areas of high winds.
Wood shingles and wood shakes are still popular in parts of the country, but these roofs require preservative maintenance every five years and may not be a good fit for areas where wood boring insects are prevalent.
Clay and concrete tiles are popular in the southwest and generally last 15-20 years. These tiles require regular maintenance, as tiles normally shift position and will crack and chip depending on weather exposure.
Finally, slate shingles are still popular in parts of the country. Slate tiles last as long as 100 years, but are brittle, expensive and can be difficult to maintain. Rounding out the most popular products are asbestos cement shingles and metal roofing. Metal roofing is growing quickly in some parts of the country. This is a product that hadn’t been used very much in residential applications except for garages and storage sheds.
Low-sloped roofs (once called flat roofs) are roofs that have a very small pitch. These roofs are subject to many more issues than sloped roofs. Drainage may be incomplete and debris often impacts runoff. Low-sloped roofs often have poor ventilation and therefore condensation and leaks can cause decay or delamination of the sheathing material (most often made of plywood or OSB, oriented strand board). As a result, most architects now require an increased slope and locate the drainage system along the outside perimeter of the roof rather than through the building. Since “through the roof” drains are surrounded by roofing materials on all four sides and are installed far away from perimeter walls, water congregates in an area where it is difficult to diagnose and where it can do a lot of damage.
Low-sloped roofing materials include both open and closed cell spray foam/polyurethane, modified bitumen, asphalt rolled roofing, EPDM (Ethylene Propylene Diene Monomer) and other synthetic rubber products, along with Neoprene, Hypalon, CPE, PIB, PVC and others.
These products have various strengths and weaknesses, but in general, the most significant areas of concern in low-sloped roofs are the seams, the edges and any area next to a roofing protrusion such as a drain waste vent, drainage vent or skylight.
All roofing materials are subject to leaks. Even the newest roof with the latest product installed must be periodically inspected and maintained to ensure peak performance. No matter what type of roof or product is installed, finding the source of the leak can be a large challenge.
The primary reason is that roof leaks often originate in a spot far away from where water is first observed. This is because water molecules are attracted to one another through the cohesive forces of capillary action and don’t show up until there is an amount significant enough to be seen. Water running through an attic often shows up far away from its exterior point of entry. Once there is enough water and it is heavy enough to drop down from a structural member such as a roof rafter, the leak may be noticed by an occupant as an interior ceiling stain. And not all “roof leaks” are from the roof. Condensation from a kitchen or bathroom vent or from a plumbing leak can also originate in the attic.
Most Frequent Causes of Leaks
- Exposed nail heads, nails improperly installed or nails not set flush with the underlying shingles.
- Improper flashing, sealing or worn-through flashing, especially around projections such as chimneys, plumbing vent pipes, skylights and dormers.
- Missing, torn or pierced shingles combined with damaged roof felt, caused by stones, hail, tree branches or human foot traffic.
- Roof valley defects such as torn or shifted material caused by temperature changes, water, foot traffic or debris.
- Wind-driven rain that lifts up shingles and flashing or pushes through attic windows, louvers, through siding or through brick mortar.
- Ice dams, which are often caused by improper attic ventilation and result from freezing, thawing and re-freezing of water in gutters.
- Improperly attached gutters and drip edges.
- Improperly installed roofing or the wrong roof materials.
- Cracking and blistering of roofing materials such as polyurethane foam, mastic, rolled asphalt or built-up roofing.
- Ponding of water caused by improper slope, sagging of the roof or debris that clogs drains and scuppers.
- Cracked or disintegrated chimney caps, missing rain caps, improper and damaged flashing.
- Missing chimney crickets on chimneys more than 30” wide and installed at the eave.
- Trim trees that overhang or are in contact with the roof surface. This will help to prevent storm damage and will help keep debris out of gutters, scuppers and roof drains.
- Direct downspouts onto splashblocks and away from the home, not against the foundation. Never direct a downspout onto another roof surface, especially in areas where water freezes.
- When replacing your roofing product, such as shingles, take the opportunity to tear off the old product so that you can take a close look at the roof sheathing. Placing another layer of shingles on top of existing shingles doesn’t allow you to see the sheathing and may create structural problems due to the excess weight. Too many layers also makes fire-fighting more difficult.
- Never nail or walk in valleys or on weak spots. Follow the manufacturer’s instructions printed on the product.
- Don’t allow different metals to come in contact with each other such as galvanized nails and copper flashing. These metals will corrode more quickly when they touch.
- Make it a practice to inspect and clean your roof, gutters, downspouts, scuppers and drains on a regular basis. You can prevent many roofing problems by simply being attentive to your roof