On older built-up roofs, there were alternating layers of heavy building paper and hot tar, covered with light-colored gravel to reflect sunlight and protect the layers from ultraviolet (UV) damage. More recently, modified bitumin (MB) has largely replaced hot building paper. MB roofs typically have cap membranes "torched on” (heated with a propane flame) to fuse them to fiberglass-reinforced interplies, or base coats.
Blisters in built-up roofs are usually caused by water trapped beneath layers of roofing. Individual blisters can be patched with three — course patches (see Chapter 5), but if blisters are widespread, it’s time to reroof.
Foot traffic, furniture, and such can abrade and puncture flat roofs. If you find no evidence of water damage below, you can spot-patch abused areas, lay down new gravel, lock the door to the roof, and consider yourself very lucky.
Most leaks occur at turn-ups, where the flat roof joins walls, parapets, and other vertical surfaces. If the turn-up surfaces are cracked, split, sagging, or unpainted, water may have gotten in and done damage. A large amount of tar at the base of walls may indicate inadequate flashing.
Cracking or blistering around downspout outlets and internal drains indicates inadequate maintenance. Are there wire baskets in the openings? Are openings free of debris? If you have doubts, flush the outlets with a hose to see how well they drain.
Is the flashing around plumbing vents sound? This is not a major repair, but it can indicate general neglect.
Although the homeowner probably won’t let you on the roof, chimneys need closer inspection than binoculars allow. Even if the chimney looks good through binoculars, make the purchase agreement contingent on a professional chimney inspection. Here’s what a pro will look for:
If the flue tile is badly cracked or if you spot shiny black creosote flakes on the roof, there’s been a chimney fire. Chances are the chimney wasn’t cleaned regularly, and combustible creosote compounds built up inside the chimney. If the chimney can’t be relined—say, with a flexible stainless-steel liner—it should be replaced. It would also be wise to ask how frequently the chimney was cleaned and how recently. If the owner claims that it was regularly cleaned, it’s fair to ask to see inspection records. Chimneys should be inspected annually, including a close inspection of the top. Better chimney-cleaning services now lower video cameras into the flue linings to show homeowners the current situation and to make recommendations for relining. More information can be found at the Chimney Safety Institute of America’s Web site (www. csia. org).
► Are mortar joints solid or crumbly? Repointing mortar isn’t a big job unless it’s badly eroded—in which case, the chimney may be unsound and so may need to be partially torn down near the top or removed all the way down to the roof ridge.
► Is there a sloping mortar chimney cap or crown at the top of the chimney, to shed water? A mortar cap is easy enough to repair, but a cracked or missing cap suggests a lack of general maintenance and, possibly, water and ice damage inside the chimney. Concrete- based caps in snow country should overhang bricks at least 1 in. (see "Overhanging Chimney Crown," on p. 194).
► If there is a prefabricated metal or concrete cap elevated above the chimney top to keep precipitation out, it too must be crack free and well attached. Elevated caps interfere with fireplace draft, so look for smoke marks above the fireplace opening.
► Is chimney flashing at the roof intact? Tired flashing can be replaced when it’s time to reroof, but missing or degraded flashing may mean rotted framing in the attic.
► To be safe, chimneys must have an intact liner (usually flue tile in older houses). If the flue is only brick and mortar instead of flue tile or if there’s creosote running down the outside of the chimney, the chimney is unsafe.
Any cracks in a flue—or no flue at all—can allow superheated gases to escape and ignite the adjacent framing.
After inspecting the roof, examine the gutters and eaves. The overhanging eaves are actually a transition from roof to wall and are composed of several building materials.
