Step Flashing on a 3 Tab Shingle in Minnesota
Before 1990, most houses were shingled with 3 tab shingles. Each row of shingles had a 5” exposure to the weather. An individual shingle measured 12” x 36” but the top 7” of the shingle is covered up by the next row up, so only 5” x 36” is left exposed. A separate step flashing is installed for each row of shingles where the shingles meet a sidewall. The flashing is positioned on each shingle so that the shingle on the next row up just covers it up. If the flashing is placed more than 2” too high it can leak.
Step Flashing on an Architectural Shingle in Minnesota
If you switch from a 3 tab shingle to an architectural shingle the step flashing needs to be adjusted to accommodate the 5 ½” exposure per row of the architectural shingle. If the flashings aren’t adjusted they will be out of sync with the new shingles and won’t be waterproof. When the original step flashings were installed, they almost always nailed them to the wall underneath the siding, so they can’t be moved. Short of removing the siding, there are a couple techniques that can be used to ensure proper flashing against a wall. Unfortunately, many roofing crews do not understand that an adjustment of some kind needs to be made to accommodate the difference of exposure per row between the 3 tab and the architectural shingles. Ask your contractor (before you hire him) how he handles this situation.
Add A Comment