Leakage at the Soil Stack and a Method of Repair

Posted by in Roof, Shingles | January 21, 2019

Noticing moisture staining or peeling paint at the top of the wall above the toilet in your bathroom? Does the damage resemble the peeling paint in Figures BR-1 and BR-2 below? Lastly, does the location of the moisture staining or peeling paint coincide with the location of the soil stack on the roof above? If you answered yes, then the damage is probably the result of roof leakage at the flashing for the soil stack.

Figure BR-1 Peeling paint at top of wall above toilet.

Figure BR-2 Peeling paint at top of wall above toilet.

Roof leakage at a soil stack is commonly the result of a split or tear in the rubber boot (Figure BR-3). Occasionally, the roof leakage is the result of roof runoff infiltrating under the shingles and leaking into the attic space at the perimeter edges of the flashing (Figures BR-4 and BR-5).

Figure BR-3 Common splitting and tearing of rubber boot at soil stack.

Figure BR-4 Flashing at soil stack. Note shingle strip at stack has been removed to expose the perimeter edges of the metal flashing.

Figure BR-5 Perimeter edge of metal flashing is unsealed. Also, the shingles are not sealed to flashing with roofing cement.

To reduce the risk of roof runoff infiltrating under the shingles and leaking into the attic space at the perimeter edges of the flashing boot, it is good construction practice to seal the perimeter edges of the metal flashing to the roof with a self-adhering waterproofing underlayment (ice guard) and to seal the edges and ends of shingles to the flashing boot with roofing cement. Ideally this is performed during the original installation of the roof shingles; however, it can be accomplished post-shingle installation by carefully removing the shingles at the soil stack, sealing the perimeter edges of existing flashing boot with overlapping strips of self-adhering flashing tape, re-installing the shingles, and sealing shingles to the flashing boot with a compatible roofing cement (Figures BR-7 and BR-8). If the leakage is due to a split boot, see our article Quick and Easy Repair for a Soil Stack Boot for a quick, inexpensive repair idea.

Figure BR-7 Perimeter of metal flashing is sealed with overlapping
strips of self-adhering flashing tape.

Figure BR-8 Shingles are re-installed at soil stack and sealed
to flashing with a compatible roofing cement.

Another job well done! Dilly, Dilly.

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