Q & A - Sealing a Roof at a Wall

Trevor’s question was, "How do I seal a roof at a wall?"

Sealing a roof at a wall is a good subject for today since I just got that question from Trevor. Here is a 10-inch cedar lap siding that is the wall covering. Trevor states the leak occurs when the flooded the roof and did not get the wall wet. That, by the way, is a good tip when searching for a leak. What we see here is a valley that drains a few inches up from a corner. I suspect there are a lot of leaves and other things piled up here.

I can only comment on what I see from your photo. After looking at the photo you sent me it appears that this is the second roof. The reason I say that is because the step flashing is not correctly in place with every course of shingles. It should have a step flash one per course and inner-laced or weave with each course. I suspect if this is a recovery the previous installer did not weave these and the water at the wall could be coming from up the wall and running down to the flat area. Before starting I would remove the shingles up about seven courses, then lay an ice and water shield making sure of a good corner and up the wall afoot. This area needs cricket flashing. I called a cricket because it kicks the water away from the dead stop and out on to the roof. If you are not familiar with bending sheet metal seek a local sheet metal man to make this for you.The corner must be soldered and slipped behind the siding running down the roof 4-6 inches. { As seen in red }

The flashing should go up the wall 6 inches and covered by the cedar siding standing off the roof at least inch. TIP – Pre-paint the front and back of the siding in this area as a great volume of water comes down to this point.

As the picture shows { As seen in blue } keep this area clear of shingles the sheet metal will help flush the debris of leaves. { As seen in green } Tuck the cricket under the last step flashing, add felt and shingle overlapping the cricket.

A dead-flat area like this needs a cricket

Installing a one-piece metal cricket should solve the problem as long as the roof is sound above this area. Keep the area clear of shingles and let the cricket work kicking the water out. Tucking the cricket under the siding is a must.

Good luck!

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