Slate Roofs Repaired in Philadelphia
A slate roof rarely wears out all at once. Slates crack or slip one at a time, and the metal around them fails before the stone does. Repaired properly, an old slate roof can keep going for years more.
Most slate roof problems in Philadelphia are repairable: a few cracked or slipped slates, a worn valley, or failed flashing at a chimney. National figures put single-slate replacement at $50 to $200 per slate, while a full slate roof replacement here runs $30,000 to $50,000 and up, so repair is usually the first thing to price.
Why Old Slate Is Usually Worth Repairing
Good natural slate outlasts the nails and flashing that hold it. When a nail rusts through, the slate slides down; when a valley's metal corrodes, water gets under the courses. Neither means the stone is finished.
The mistakes we see most are repairs done with the wrong materials: tar smeared over cracked slates, roofing cement in valleys, or asphalt shingles patched into a slate field. They stop a leak briefly and make the next repair harder.
What Moves the Cost of a Slate Repair
- Number of slatesA handful of slates is quick; a whole slope is not.
- MatchingSalvaged slate of the right size and color takes sourcing.
- Valleys and flashingCopper liners and wall flashing add material and labor.
- Height and pitchSteep, high slate roofs need staging and roof brackets.
- Walking the roofSlate breaks underfoot, so access is set up carefully.
National figures put typical slate roof repairs at $800 to $3,200, and a full historic slate roof in Philadelphia at $30,000 to $50,000 and up. These are planning ranges, not our quote.
Individual Slate Replacement
A cracked, broken or slipped slate is replaced by removing the pieces with a slate ripper, which cuts the old nails without disturbing the slates above. The new slate is matched for size, thickness and color, often from salvage stock, and held with a copper hook or a nail covered by a small metal bib. Tar and cement are not part of the repair. Published national figures put single-slate replacement at $50 to $200 per slate, depending on access and matching.
Slate Valley and Flashing Repair
Valleys on older slate roofs were lined with metal that corrodes long before the slate wears out. A leaking valley shows as a stain in a line running down from the roof's inside corner. The fix is carefully removing the slates along both sides of the valley, installing a new valley liner, often copper, and relaying the same slates. Chimney and wall flashing on slate roofs follow the same approach: new metal woven in, slates reset, no cement over the joint.
Slate Roof Ridge and Hip Repair
Ridges and hips on slate roofs are finished either with slate saddles or with a metal ridge cap over a wooden ridge pole. Mortar or old tar used to bed them cracks out over time, and wind lifts loose pieces. Water entering at the ridge often shows up high on a top-floor wall. We rebed or refasten slate saddles, or replace a failed metal ridge cap with new copper or coated steel. It is one of the highest and most exposed parts of the roof.
Slates slipping off the roof?
Call and we reset them before water gets under the courses.
What We See on Philadelphia Roofs
Tacony and Wissinoming were built as the first residential streets of the Northeast, for workers at Disston Saw Works and nearby mills, and the Lower Northeast rows that followed in the 1920s and 1930s often still carry slate. Around Oxford Circle, too, a slate roof over a 90-year-old system is common. On those houses the slate is often fine and the nails, valleys and flashing are what need attention.
How a Slate Repair Runs
- 1
Inspect from ladders and attic
Slate is not walked on casually; we check from below first.
- 2
Photograph and scope
Broken slates, valleys, flashing and ridge noted.
- 3
Source matching slate
Size, thickness and color matched, often from salvage.
- 4
Set up access
Roof hooks and brackets so slates are not trodden on.
- 5
Replace and reflash
Slates hooked or bibbed in, valleys and flashing renewed.
- 6
Clear and check
Broken pieces removed, gutters checked for debris.
Signs a Slate Roof Needs Repair
Slates out of line
A slipped slate means its nail has rusted through.
Pieces in the gutter or yard
A slate has broken or fallen.
Stains below a valley
The valley metal is corroding.
Tar patches on the slate
Past quick fixes that trap water.
Dark streaks at a chimney
Flashing is failing at the joint.
Daylight in the attic
Slates are missing or badly cracked.
Slate Roof Questions
Real slate is heavy, cold and rings when tapped. Synthetic slate is lighter and sounds dull. We confirm on inspection.
Yes. Salvaged slate usually matches best; new stone may look slightly different until it weathers.
Only if the slate itself is failing across the roof. Most slate roofs need repair, not replacement.
Please do not. Slate cracks underfoot. Work from a ladder or call us.
Historic-listed buildings need a fuller permit review for roof work. Like-for-like slate repair is usually the expected approach.
More Replacement & Installation Work in Philadelphia
From our guides: Repair or Replace Your Roof?
Keep Your Slate Roof Going
Call for an inspection. We repair slate with slate and metal, not tar.