ISSUE
Some roofs feature pitch changes, whether from steep to low pitch, as is the case with a gambrel roof, or from low to steep pitch, such as is the case over a dormer.
ANALYSIS
The handling of such pitch changes must be done properly and is usually specified by the manufacturer of various products.
SOLUTION
Unless the pitch change is extremely small, standing seam and other vertical roofs must actually be stopped and re-started at pitch changes. With horizontally-run products, though, if the pitch change happens to fall at the top of a course of shingles and if the change in pitch does not exceed a difference of more than 3 or 4:12, the pitch change can often be accomplished just by keeping the panels interlocked and continuing on up the roof. When this is done, care must be taken to ensure that the shingles at the pitch change are fully interlocked. Doubling up on fasteners and, if present, fastening clips, on the two courses above and two courses below the pitch change can be beneficial. If the metal roofing must actually be stopped and re-started at the pitch change, the flashing must be designed so that water always stays on top of the metal system and is not trapped or channeled beneath the panels. The flashing must also be large enough to ensure that water cannot blow up underneath the flashing and enter at the pitch change. Installing sealant as a waterbreak beneath the flashing can be helpful. Generally, though, such flashings should be at least 6” in width.
