There’s a moment on every old-house roof job that we’ve learned to plan for. The first section of shingles comes off, somebody on the crew goes quiet for a second, and then you hear it: “Hey — come look at this.” On a house built in 1995, that moment almost never happens. On a house built in 1895, it happens before lunch.

We’ve roofed a lot of century-old homes across the Seacoast — Federal-style capes in Portsmouth’s South End, farmhouses on the back roads of Kingston and Newfields, the big Victorians up the hill from downtown Exeter, mill-worker duplexes in Dover and Newmarket. They’re some of our favorite jobs. They’re also the ones where the difference between a good contractor and a bad one shows up in the first two hours. So this post is about roofing a 100-year-old house in NH: what’s usually hiding under the shingles, what it costs to deal with, and how to tell whether the quote you’re holding accounts for any of it.

Why Is Roofing an Old House Different From a Newer One?

People assume “old” means “fragile.” That’s mostly backwards. The framing in a 1900 Exeter farmhouse is full-dimension, old-growth lumber — a true 2×6 rafter from 1900 is stronger than anything you can buy at a lumberyard today. The problem isn’t strength. It’s that the whole roof system was designed around materials and a building science we don’t use anymore.

A cedar shingle roof needs air on its back side to dry. So the deck was gapped boards, not solid sheathing. There was no underlayment, because felt would have trapped moisture against the cedar. There was no ice and water shield, because it didn’t exist. There was no ridge vent or soffit intake, because a house with single-pane windows, no insulation and balloon framing moved so much air through the attic that it never got damp enough to matter.

Then, over 100 years, people did sensible things to that house. They insulated. They put in tight windows. They sealed the walls. And somewhere along the way somebody nailed asphalt shingles right over the cedar — sometimes twice. Now you’ve got an attic that can’t breathe, a deck that was never meant to hold asphalt, and three layers of roofing you can’t see. That’s the house we walk up to.

What Do We Actually Find Under the Shingles on a Pre-1930 Home?

1. Board sheathing — and sometimes skip sheathing

Plywood didn’t show up on residential roofs in New England until the late 1940s, and it wasn’t universal until the ’60s. So a 100-year-old roof has a deck made of individual boards — usually rough-sawn pine or hemlock, 1×6 to 1×10, nailed across the rafters. Two versions exist. Tight board sheathing is boards butted up against each other; it’s a perfectly good nail base if the boards are sound. Skip sheathing is boards with deliberate gaps of 2 to 6 inches between them, which is what cedar shingles were laid on. You cannot nail asphalt shingles over air.

The tell is easy once you know it. Go in the attic with a flashlight, look up, and if you can see the underside of the roofing between the boards, it’s skip sheathing. We pulled the roof on a house near the Squamscott in Newfields last fall where the skip sheathing gaps were so wide the previous roofer had just nailed asphalt across them anyway. Every third nail was hanging in space. The shingles had been sliding downhill for years.

2. A cedar roof nobody mentioned

Under the asphalt on a lot of these homes is the original wood shingle roof. Nobody stripped it — they just went over it in the 1960s or ’70s. Cedar buried under asphalt for 50 years comes out black, powdery and often crawling with carpenter ants. It also means an extra tear-off layer, an extra dumpster, and a deck we can’t evaluate until the cedar is gone. We can usually spot it from the rake edge — a wood shingle layer makes the roof edge look thick and stepped — but we don’t price it until we’ve confirmed it.

3. Two, three, sometimes four layers

The current NH residential code caps a roof at two layers. Old houses predate that rule by decades, and we’ve stripped four-layer roofs in Dover and Somersworth: cedar, then two rounds of 3-tab, then architectural on top. Every layer adds weight the rafters were never sized for, and it hides everything below. If you want the full argument for why we never go over an existing layer, we wrote it up separately — but on an old house it isn’t even a debate. There’s no way to inspect the deck without taking everything off.

4. Rotted rafter tails and eave boards

The bottom 12 to 24 inches of an old roof takes the worst beating: ice dams back water under the shingles, gutters overflow, and on the Seacoast, salt-laden wind drives rain up under the eaves. Century-old rafter tails are frequently punky, and the first course of sheathing boards along the eave is rotted through more often than not. Fixing it means sistering a new 2×6 or 2×8 alongside each bad rafter tail and replacing the eave boards before the drip edge goes on. It’s not dramatic carpentry, but it’s carpentry, and it needs to be on the quote.

5. The chimney

Almost every 100-year-old Seacoast home has a center chimney or two, and almost every one of them has been leaking longer than the current owners have lived there. The flashing is tarred-over sheet metal from three roofs ago. The mortar joints above the roofline are soft enough to scrape with a fingernail. There’s no cricket behind the chimney, so snow sits against the brick all winter. We pulled the shingles around a big center chimney on a Portsmouth house near Middle Street two summers ago and found the deck rotted in a perfect four-foot semicircle behind it — you could see exactly where the water had been pooling every winter for a couple of decades.

6. No ventilation whatsoever

No soffit vents. No ridge vent. Maybe a gable vent at each end, maybe not. On a house that’s since been insulated and tightened up, that’s why the underside of the deck is stained black and the nail tips grow frost in January. It’s also why the last asphalt roof failed early, and why the next one will too unless it’s fixed during the re-roof.

7. Asbestos-cement shingles

A handful of times a year we walk up to a gray, brittle, diamond-pattern or rectangular roof shingle that goes clink when you tap it. That’s asbestos-cement, sold from the 1920s to the 1970s. They’re harmless sitting there, but the tear-off has to be done by a licensed abatement contractor under state rules before we touch the roof. It adds cost and about a week. We’d rather tell you that at the estimate than the morning of.

Does Old Board Sheathing Need to Be Replaced With Plywood?

This is where a lot of old-house quotes go wrong in one of two directions. Some contractors overlay every old roof with plywood no matter what, which is easy money on a deck that didn’t need it. Others don’t mention the deck at all, then hand you a change order on tear-off day. We do it the boring way: we tell you up front what we expect based on the attic inspection, we put a per-sheet price for plywood in the contract, and we photograph every sheet we install so you can see exactly why.

Our rule of thumb, and it’s the one every shingle manufacturer uses too: nominal 1×6 or wider boards, sound, with gaps no more than 1/4 inch — shingle over them. Anything else gets plywood. On a typical Seacoast cape or farmhouse that means one of three outcomes:

• Sound tight boards (maybe 30% of homes): replace a handful of bad boards along the eaves, shingle directly. Cheapest path.
• Mixed condition (about half): replace bad boards, then overlay the whole slope with 1/2″ CDX so the nail base is consistent. This is the most common outcome.
• Skip sheathing (the remainder): full plywood overlay, no exceptions. On a 25-square roof that’s roughly 75–80 sheets.

One thing we do not do: rip out old board sheathing and replace it with plywood. The boards are the structure. They’re nailed with cut nails into old-growth rafters and they’re not going anywhere. Overlaying is faster, cheaper and stronger than demolition.

Why Does a Century-Old House Need Ventilation Added During a Re-Roof?

The exhaust side is straightforward. We cut a slot at the ridge and install a ridge vent under the cap shingles, same as any modern roof. The intake side is where old houses get interesting, because many of them don’t have a soffit at all — the rafter tails are exposed, or the eave is a tight crown-molded box with no room for a vent. Depending on the house we’ll use continuous vented soffit where there’s a real overhang, individual round or rectangular soffit vents cut into a boxed eave, or an edge-of-roof intake vent that sits under the first course of shingles when there’s no overhang to work with. Baffles get stapled between the rafters so the new insulation doesn’t choke the intake off.

And this is the part homeowners don’t expect: if the bathroom fan vents into the attic — which on a house renovated in the ’80s is about a coin flip — we run it out through the roof or a gable wall while we’re up there. Blowing shower steam onto the underside of a brand-new deck is how you get to do this all over again in 12 years.

How Much Does It Cost to Roof a 100-Year-Old House in NH?

Here’s roughly how the old-house line items break out on a 25-square roof (about 2,500 sq ft of roof surface, typical for a Seacoast cape or farmhouse with an ell). None of these are guesses — they’re what these items have been costing on our jobs in Rockingham and Strafford County this year.

Ranges reflect Compass Exteriors 2026 pricing on Seacoast and Southern NH jobs. Every quote is built from an in-person roof and attic inspection, not a satellite measurement.

Add that up on a house that needs a cedar strip, a full plywood overlay, chimney work and ventilation, and you’re looking at $5,000–$9,000 on top of the base roof. That’s a real number. It’s also the number that turns a 15-year roof into a 30-year roof, and it’s a lot less than the redecking bill you get when the next roofer finds what the last one buried.

What Roofing Material Makes Sense on an Old Seacoast Home?

We have opinions here. Owens Corning Duration in Onyx Black or Estate Gray, or CertainTeed Landmark in Moire Black, on a 1900 farmhouse looks right and nobody driving past will ever think about it. Fancy multi-tone “designer” shingles on an old cape look wrong every time. Keep it dark, keep it flat, let the house be the point.

If you’re in Portsmouth’s Historic District or one of the Exeter overlay areas, don’t let a contractor tell you that you’re stuck with slate or cedar. Architectural asphalt gets approved routinely on non-street-facing slopes and often on the whole house; we’ll help with the Certificate of Approval paperwork before the job is scheduled. Standing seam metal and synthetic slate are the other two that clear those reviews most often.

One specific note for homes within a mile or so of the water in Rye, Hampton, North Hampton and Portsmouth: if you go metal, spec aluminum rather than galvalume steel, and make sure the fasteners are stainless. Salt air off the Gulf of Maine finds cut steel edges faster than any manufacturer brochure admits.

What Mistakes Do Homeowners Make Roofing an Old House?

1. Comparing quotes that aren’t the same job. A $16,000 quote and a $24,000 quote on the same old house usually aren’t a $8,000 difference in markup. One of them has plywood, chimney work and ventilation on it and the other one has a change order waiting. Ask every contractor to itemize the old-house work, then compare.
2. Allowing a layover. On a house with unknown layers and an uninspected deck, shingling over the top is the single worst decision you can make. You just sealed the problem in for another 15 years.
3. Skipping ventilation. “The roof lasted 100 years without it” — no, the cedar roof lasted 40 years without it, and the two asphalt roofs since then each lasted about 15. The house changed. The roof system has to change with it.
4. Ignoring the chimney. New shingles wrapped around soft brick and tarred flashing is a leak with a countdown timer. If the mason needs to come first, the mason comes first.
5. Hiring off a drone photo. Nothing in this post can be seen from the air or the street. Board gaps, black staining, frost lines, rafter tails — you find those in the attic and on the roof with your hands. If your estimator didn’t go up, the number is a guess.

How Long Does It Take, and What Should You Expect?

Day one is tear-off, and on an old house it’s a big day: multiple layers, a hundred years of dust, and the first honest look at the deck. We photograph everything that afternoon and walk you through it before any plywood goes on — you approve the sheet count against the per-sheet price that’s already in your contract. Day two is carpentry and dry-in: eave repairs, overlay, ice and water shield (we run it a minimum of 24 inches inside the warm wall, and full-slope on anything under 4/12 or on the north side of a chimney), synthetic underlayment, drip edge, new step and counterflashing. Day three, sometimes four, is shingles, ridge vent, soffit intake and cleanup with the magnet sweep. Old houses shed a shocking number of hundred-year-old cut nails.

Plaster ceilings deserve a mention. Tear-off on a board-sheathed roof vibrates the whole frame, and horsehair plaster that’s been hanging on since McKinley can shed a little dust or hairline crack. It’s rare, but take down anything fragile hanging on the top-floor walls and cover the beds. We’ll tell you the same thing at the pre-job walk.