Chimney Leak on a Tile Roof
A tile roof intersects a masonry chimney on a 6/12 slope. The chimney is 36 in. wide measured parallel to the ridge and penetrates the roof about 4 ft above the deck. The existing step flashing is 26-gauge galvanized, but each piece is nailed directly to the roof deck through the face, and the top edge is sealed to the masonry with roofing cement. There is no cricket, no counterflashing, and the tile covers the flashing so that only 2 in. of metal is visible. The chimney has a concrete cap but no cap flashing. During a rain test, water appears at the ceiling near the chimney corner, and the homeowner reports the leak occurs during wind-driven rain. The roof has one layer of 30-lb felt under the tile, and the felt terminates at the chimney face without being turned up.
1. What are the likely leak paths and flashing deficiencies?
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The chimney is 36 in. wide, so it needs a cricket on the uphill side; without one, water ponds and drives under the flashing. Nailing step flashing through its face creates holes and also fastens the metal tight so it cannot move independently; the top edge sealed with cement is a maintenance seal, not counterflashing. No counterflashing means wind-driven rain can enter the masonry-to-flashing joint. The felt terminating at the chimney face without a turn-up leaves the deck edge unprotected. The visible 2 in. of metal suggests the tile may not be properly overlapped and the flashing may not extend high enough. Likely paths are at the uphill corner where water concentrates, through nail holes, behind the step flashing, and at the masonry joint. Wind-driven rain makes the masonry joint and missing counterflashing the prime suspects.
2. Describe the correct repair sequence and details.
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Remove tiles and old flashing around the chimney, taking care not to damage surrounding tile. Inspect and replace any rotted deck. Install a cricket on the uphill side, sloped to drain, with its flashing integrated into the field underlayment. Install new step flashing in shingle fashion, starting at the eave and lapping each piece over the one below, fastened only at the upper edge and not through the face; the flashing should extend under the tile and up the chimney. Cut a reglet into the masonry and install new counterflashing, with a sealant bead at the top, not at the bottom, so water can drain. Turn up the underlayment at the chimney. Replace tiles with proper overlap. Water-test before final sign-off. Use corrosion-resistant metal compatible with masonry.