How does an inspector tell whether there is still slate under the shingles?

From the attic first: boards laid with gaps between them were sized for slate, not for a continuous shingle deck. Then from the eaves, where slate debris collects in the gutters, and from the rake, where the edge profile shows what was covered rather than removed. It changes the whole quote that follows, so it belongs on the first page of the report.

On a twin or a rowhouse, does the inspection stop at the property line?

The flashing joint at the party wall is shared, so the honest answer is no. An inspector who only looks at your half is looking at half of the detail most likely to leak, and the report should say what the other side looks like from the roof.

Is a winter inspection worth anything here?

For the attic, yes. NOAA's records for Philadelphia average about seventy nights at or below freezing and roughly twenty inches of snow a year over the last decade. That is enough freeze and thaw to leave ice marks at the eaves and along the porch roof in February. The covering itself waits for a dry day.

What should the written report say about the porch roof?

That it is a separate roof: its own material, its own age, its own slope, and usually the first thing on the house to leak. A report that folds it into the main roof has not walked it.

What kind of finding actually fails an inspection on a house like this?

Slate that flakes or shatters when handled rather than just chipping, counter-flashing sealed to the brick face instead of cut into the mortar, spaced sheathing left unaddressed under modern shingle, and a porch roof with visible ponding or open seams. On this housing stock those items show up more often than a worn field does, and a report naming them is worth more than one that just says the roof looks old.

Why do I keep getting unsolicited calls about a free roof inspection?

Those calls are almost always generated from a list of addresses rather than from anyone who has looked at your specific roof, and they tend to increase after any stretch of bad weather rolls through the area. A real inspection is one you arrange yourself, produces a written report with photographs, and answers a question you actually had, not a pitch that starts with a knock at the door.

Roof inspection

An inspection earns its cost when it answers a decision you are about to make. In a region where a roof can be slate, composition over slate, or three layers of composition over spaced boards, the most valuable thing an inspection produces is simply knowing what is actually up there.

When it earns its price

Before buying an older house: roof condition is one of the largest numbers hiding in a purchase, and around here a home inspector’s two-line note about the roof rarely distinguishes between slate with thirty years left and slate that is done.

When slate is in question: the difference between a repair and a full conversion is enormous, and it deserves someone who works the material rather than someone who sells the alternative. And near the end of a composition covering’s life, when the real question is “this season or in three years” and a documented answer beats a guess in either direction.

What gets checked

On the surface: the covering itself and what it actually is; the valleys and what is sitting in them; step and counter-flashing at every chimney, with attention to whether the counter-flashing is cut into the mortar or sealed to the face; the party-wall junction on attached houses; the porch or low-slope sections and their material; and the eaves, fascia and gutter line where a treed lot does its damage.

In the attic, which matters more here than in newer markets: whether there is any ventilation at all, whether soffit intake was buried by insulation, the condition of the sheathing from below (and whether it is spaced boards), staining or rusted nail tips from condensation, and fans ducted into the attic instead of outside. On a house of this age, the attic is where half the story lives.

What the report is good for

The report is what makes three bids mean anything. Same sheathing, same porch, same chimney, priced from the same documented findings rather than from three quick looks off the driveway. On housing this old that is the difference between comparing prices and comparing guesses, and when slate is involved the numbers at stake are large enough that the distinction pays for the inspection several times over. Dating the findings matters too, because the trades you need here book months ahead.

What to expect from an inspection on an older Philadelphia-area house

How does an inspector tell whether there is still slate under the shingles?: From the attic first: boards laid with gaps between them were sized for slate, not for a continuous shingle deck. Then from the eaves, where slate debris collects in the gutters, and from the rake, where the edge profile shows what was covered rather than removed. It changes the whole quote that follows, so it belongs on the first page of the report.
On a twin or a rowhouse, does the inspection stop at the property line?: The flashing joint at the party wall is shared, so the honest answer is no. An inspector who only looks at your half is looking at half of the detail most likely to leak, and the report should say what the other side looks like from the roof.
Is a winter inspection worth anything here?: For the attic, yes. NOAA's records for Philadelphia average about seventy nights at or below freezing and roughly twenty inches of snow a year over the last decade. That is enough freeze and thaw to leave ice marks at the eaves and along the porch roof in February. The covering itself waits for a dry day.
What should the written report say about the porch roof?: That it is a separate roof: its own material, its own age, its own slope, and usually the first thing on the house to leak. A report that folds it into the main roof has not walked it.
What kind of finding actually fails an inspection on a house like this?: Slate that flakes or shatters when handled rather than just chipping, counter-flashing sealed to the brick face instead of cut into the mortar, spaced sheathing left unaddressed under modern shingle, and a porch roof with visible ponding or open seams. On this housing stock those items show up more often than a worn field does, and a report naming them is worth more than one that just says the roof looks old.
Why do I keep getting unsolicited calls about a free roof inspection?: Those calls are almost always generated from a list of addresses rather than from anyone who has looked at your specific roof, and they tend to increase after any stretch of bad weather rolls through the area. A real inspection is one you arrange yourself, produces a written report with photographs, and answers a question you actually had, not a pitch that starts with a knock at the door.

An old roof rarely gives out in the field. It gives out at the joints and the edges. Where the work actually happens on a roof.

Tap to enlarge

1 Ridge caps. Thin, fully exposed, and usually the first course to let go.
2 The field. Slate on the older rows, shingle on the rest, each on its own clock.
3 Valleys. Two slopes emptying through one line, with litter holding the water there.
4 Flashing. Old masonry, and the party wall a rowhouse shares with the house next door.
5 The vent boot. A small rubber part with a far shorter life than the roof it sits in.
6 Eaves. Where the porch roof ties into the wall, and where backed-up water gets in.

The rest of the work

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