Sewickley's
Roofing Specialists

The river valley holds moisture and swings across freezing far more often than the ridgetops do. Water works into slate seams, hairline flashing gaps and old mortar joints, freezes overnight, expands, and levers those gaps a little wider. Do that forty times a winter for a hundred years and you get the failure pattern we see on nearly every Sewickley roof: the field is still sound, and the flashings and valleys are done.

So we detail the water paths differently. Wider valley metal with a hemmed edge instead of a pinched W-valley. Soldered copper where two dissimilar planes meet, not caulk. Step flashing woven into each course at chimneys and walls instead of a single bent apron sealed at the top. Ice-and-water membrane carried well past code minimum at eaves, valleys and every penetration. None of that shows in a photo, and all of it is the difference between a roof that lasts and a roof that leaks in year four.

The valley walls put a lot of Sewickley and Edgeworth homes in shade for most of a winter day. A north slope that never sees sun stays frozen at the eave while heat escaping the attic melts snow higher up. That meltwater runs down, hits the frozen edge, and backs up under the shingles.

Fixing that means fixing the attic, not just the roof. Historic homes here typically have minimal insulation, no baffles, blocked or nonexistent soffit intake, and bath fans dumping warm wet air straight into the attic. We air-seal the ceiling plane, restore intake and exhaust so the deck stays cold, and add membrane at the eaves as backup. If a contractor's answer to your ice dams is heat cable, they are treating a symptom and billing you every winter for it.

Sewickley and Edgeworth are shaded by mature hardwoods, and the roofs pay for it. Valleys and gutters pack with leaves and twigs, so water backs up sideways under shingle edges. Shaded slopes grow moss and algae. Limb strikes crack slate and bruise asphalt.

Moss is the one people underestimate: it holds water against slate and freeze-thaw then delaminates the stone in layers. We remove it by hand and with low-pressure treatment — never a pressure washer, which strips the surface and drives water under the courses. Then we set up a real maintenance rhythm: valleys and gutters cleared twice a year, guards where they actually help, and limbs trimmed back off the roof plane.

Sewickley Heights sits well above the valley floor, and the wind up there is a different problem than anything the borough homes deal with. Uplift concentrates at ridges, rakes and hips, and long unbroken slopes act like a wing.

That changes the fastening, not just the material. Increased nailing patterns, starter course at rakes as well as eaves, mechanically fastened ridge caps rather than the minimum, and hip-and-ridge products rated for the wind speed we actually get on that ridge. On slate and metal work up there we upgrade the fasteners and the clip spacing rather than following the sheltered-valley default.