Roof replacement
Replacing a roof on housing this old is mostly a question of what is underneath. The covering is a decision anyone can make; the deck, the metal and the edge detail are where two honest quotes separate by thousands.
What the tear-off is going to find
On anything built before the war, spaced sheathing is common: boards laid with gaps, sized for a material that was hung rather than nailed flat. A modern covering needs a continuous surface, so re-sheeting is frequently part of the job rather than an exception. It should be priced before the roof is opened, not discovered on day one.
Layers are the second unknown. Re-covering was normal for decades, and a house can be carrying two or three generations of material. The honest quote states what it assumes and what happens if the assumption is wrong.
The parts of the roof that are not the covering
On a row or a twin, the party wall rises through the roof plane and its flashing is the single most common entry point. Rebuilt properly it outlives the covering; sealed, it becomes a maintenance item. The quote should say which.
On a house from the twenties or thirties, look at the valleys and the chimney before agreeing to a full tear-off. Copper of that era is often in better condition than anything around it, and a replacement that discards it is discarding the component that has outlasted everything around it.
And on almost every older house here, the rear ell has a much shallower pitch than the front. It is effectively a second roof needing a different product, and it is where the leaks usually are.
Reading two quotes on the same house
The spread is rarely the shingle brand. It is whether re-sheeting is priced, whether the rear section is specified separately, whether flashings are rebuilt or sealed, whether existing metal is kept, and whether access on a narrow street has been accounted for.
The comparison tool on this site walks those points one at a time.
What to ask every bidder
- What happens if the sheathing is spaced rather than solid?
- On pre-war housing that is likely rather than possible. Ask for the price per sheet of new decking before the roof is opened.
- How is the rear roof specified?
- The shallow section behind the steep front is a different roof with different materials. A single specification for the whole house under-serves it.
- Is the party wall flashing rebuilt or sealed?
- On a row or twin this is the most common leak point. Rebuilt metal outlives the covering; sealant under this sun and this freeze cycle does not.
- Is there sound copper, and what happens to it?
- On many houses of a certain era the valleys and chimney flashing are copper and still good. Removing them by default is a real loss, and it should be a decision.
- 1 The ridge. The highest course, and on slate the one most often reset by hand.
- 2 The field. Slate on the older stock, shingle on the rest. Two very different clocks.
- 3 Valleys. Where leaf litter settles, and where a slate roof usually ends its life.
- 4 Wall flashing. The party wall of a row or twin, rising through a roof two houses share.
- 5 Penetrations. Holes cut on purpose. When access is awkward they get sealed instead of rebuilt.
- 6 The overhang. Where meltwater from a warm attic reaches cold framing and stops.