Is Your Roof Vulnerable to Leaks?
By: New Jersey Home Inspector Michael Del Greco
Is Your Roof Vulnerable to Leaks?
Submitted by: Michael Del Greco, New Jersey Home Inspector Lic GI 0121, President of Accurate Inspections, Inc, a New Jersey home inspection company
When you hear of roof leaks, your first thought is probably directed to the roof covering, such as the asphalt shingles. You may be surprised to hear that approximately 60 percent of all leaks occur at joints, valleys or projections through the roof.
Typical leak locations are at chimneys, plumbing vents, roof valleys, dormers, joints where a roof meets a wall, skylights, and parapet walls. In short, any time you have a roof penetration or projection, you have a more vulnerable area.
Of the remaining 40 percent of roofing problems, approximately 25 percent of roofing failures are due to worn, deteriorated roofing materials. The remaining 15 percent is due to improper roofing material applications, poor workmanship and miscellaneous items.
The remedy for most problem areas is properly installed flashings. Step flashings are typically aluminum ``L-shaped\'\' pieces used to divert water away from the projection or roof penetration. Proper flashings and workmanship should develop a condition where the flashings will be dependable for the life of the roof covering and beyond.
In most instances, proper flashings are made up of step and counter-step flashings. The first piece on a step flashing is the ``L-shaped\'\' piece mentioned above. The average size is 7\" long and 5\" wide. It is bent into the 7\" length, with 3\" and 2\" on each side. This step flashing is placed with the 3\" side against the roof shingles and the 2\" side placed vertically against the wall or chimney, etc.
The second piece, known as a counter flashing, covers the vertical portion of the step flashing to keep water deflected away from the top of the step flashing. At a wall, the siding will act as an apppropriate counter flashing.
At a chimney, the counter flashing looks like an inverted ``L\'\' with the short 3/4\" portion being inserted into the brick or masonry joints after the mortar has been cut out.
Skylights should be installed on a curb to allow room for proper flashings and should never be installed level at the roof surface. The height of the curb is dictated by the slope of the roof (i.e., roofs with a slope of 4/12 to 6/12 should have a curb of at least 4\"). Skylights on flat or nearly flat roofs should have a curb of 8\" or more depending on possible snow accumulation.
Roofs that do not allow water to drain successfully are prone to problems at seams and premature deterioration. Ponding is generally not considered acceptable if it does not evaporate within 48 hours after a rain.
Problem areas should be addressed as soon as possible due to the unavoidable interior damage that will typically occur (e.g., roof sheathing, drywall or plaster and wood-framing components).
Valleys are dependable if the proper materials are used and the workmanship is acceptable. Valleys are vulnerable because a large percentage of the water that hits the roof accumulates in the valleys. This creates a disproportionate amount of wear. It is not unusual for the valleys to wear out ahead of the shingles.
Information provided by Michael Del Greco, New Jersey Home Inspector Lic. GI 0121, American Society of Home Inspectors Member 102273, Pesident of Accurate Inspections, Inc. A West Paterson New Jersey Home Inspection firm.