Q: We recently had a new roof, windows and siding installed on our two-story home. All of the old shingles were removed and replaced with a 25-year-warranty shingle. We then had new vinyl siding installed over the old wood siding as well as new vinyl-replacement windows. We are now experiencing problems with roof leaks in our family-room addition. This is a one-story addition built several years ago, and it has never leaked before. We only noticed the leaks after the siding was installed. Do you have any suggestions as to why this is happening? The siding people say it's the roofer's problem, and the roofer blames the siding contractor. Any helpful suggestions would be appreciated.
A: What you are experiencing is the "last-man-in syndrome," or the last person to work on your home caused all the damage. This is not always true. Where a one-story roof butts up against the wall of a two-story structure, the roofer should have installed step-flashing and counter-flashing to keep water from running down the wall where it will flow under the shingles.
Roof shingles are 12 inches high and generally have 5 to 6 inches of exposure, as one shingle overlaps the shingle below. As the shingles are installed against the second-story wall, a small 4-inch-by-8-inch folded piece of metal flashing is laid on top of the shingle before the next one is installed. The flashing covers 4 inches of the shingle and extends approximately 4 inches up the wall. Because the flashings overlap each other, they are installed in a stair-step manner, thus the term "step-flashing."
Because the roof and the wall will expand and contract at different rates, it is important for the flashing to be nailed to the roof and not to the sidewall. This will leave loose pieces of flashing exposed on the sidewall. To prevent leaks, a piece of metal flashing 6 to 8 inches high and no more than 10 feet in length is installed over the loose wall flashing and attached to the wall only, but the fasteners should never penetrate both the counter-flashing and the wall-flashing. This would defeat the purpose of allowing the two flashings to expand and contract at different rates without buckling.
It is possible that the siding contractor nailed both together when he installed the J-channel trim, which is normally installed at the bottom of the siding. It is also possible that the roofing contractor eliminated the counter-flashing, because the new vinyl siding would act as the counter-flashing, but this would be a mistake because of the nailing of the J-channel.
One sure way to avoid pesky roof leaks at adjoining walls is to install a rubberized, self-adhesive product, such as Grace Ice & Water Shield, in place of the metal flashings. The shield extends 18 inches or more up the sidewall and extends as far as necessary on to the roof's decking. Once the shield is installed, the roof shingles are installed and then the siding. The rubberized shield self-seals any nails that penetrate the material, preventing the possibility of leaks at the penetrations.
Using Ice & Water Shield will guarantee no more leaks. You can find additional information on Grace Ice & Water Shield at www.na.graceconstruction.com/.
(Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home-improvement questions at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 286, Evansville, Ind., 47702, or e-mail him at d.barnett(at)insightbb.com.)
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