Roof Decking Replacement Cost: When the Deck Has to Go
The decking, or roof sheathing, is the wood the shingles are nailed to: 4x8 sheets of OSB or plywood, or on older homes 1x boards, spanning the trusses. Nobody sees it between roofs. When a roof comes off, it's the one part of the job that can't be priced until the shingles are gone, and roof decking replacement cost is the line that separates a $16,000 quote from a $17,800 invoice. Here's what fails, how a contractor finds it, and what it costs on a Littleton house.
What the deck is made of, by era
- Pre-1965 houses in Old Littleton, Woodlawn and Bow Mar: 1x6 or 1x8 boards, solid or spaced. Solid boards are fine as a nail base. Spaced boards (skip sheathing) were for shake, not shingles.
- 1965–1985 in Southpark, Ridgewood, Columbine, the Ken Caryl Plains: plywood, usually 1/2 inch. Good material that lasts if it stays dry.
- 1985 onward in Highlands Ranch, Centennial and the Ken Caryl Valley: OSB, 7/16 inch. Perfectly adequate when dry. Swells, delaminates and loses nail-holding when it gets wet repeatedly, and it gets brittle with age.
On the OSB vs plywood roof deck question for new sheets: both are accepted at the right thickness. Plywood tends to tolerate repeated wetting a little better; OSB is cheaper and more uniform. What matters more is that the quote names one, gives a thickness, and prices it per sheet.
The four ways decking fails here
Water. A pipe boot that leaked for three winters, a valley on felt, an ice dam on the north eave every March — the OSB under it swells, goes soft, and stops holding nails. Rotted roof decking like that feels spongy underfoot and shows as dark, flaky wood from the attic. The typical pattern on a South Metro tear-off is one or two soft sheets at a penetration and a soft strip along the north eave.
Hail. Large hail — the 2-inch stones the June storms drop every few years — fractures OSB through the shingles. You can't see it from above. From the attic, with a flashlight held at a low angle, the underside shows small broken spots. A hail-fractured deck can't be re-shingled; the nails have nothing to bite, and the adjuster's scope should include it.
Delamination and age. Thirty-year-old OSB on a south slope, baked at altitude through thirty summers, sometimes just comes apart in layers when the shingles are stripped. It's dry, it's not rotten, and it still can't hold a nail.
Skip sheathing. When a cedar shake roof comes off in Ken Caryl Valley or Columbine Valley, what's underneath is 1x4 boards with 4-inch gaps. Shingles need a solid deck. The whole roof gets overlaid with 7/16 OSB before the underlayment goes on.
How a contractor finds it
Before the tear-off: from the attic on the inspection, looking for stains, daylight, fractures and soft spots between rafters. From the roof, feeling for sponginess underfoot at the eaves, valleys and around penetrations. This gives the contractor an estimate — "expect two to four sheets" — that goes in the quote as an allowance.
During the tear-off: every sheet gets walked once the shingles are off. Soft, delaminated or fractured sheets are marked, photographed, and cut out. You should get the photos. If a sheet is borderline, a careful crew leans toward replacing it — it's about $120 now or a nail-pop leak in year four.
Roof decking replacement cost in Littleton
| Decking work | Typical Littleton price |
|---|---|
| Replace one 4x8 sheet of 7/16 OSB, installed | $90 – $150 |
| Replace one sheet of 1/2 plywood (to match an older roof) | $110 – $180 |
| Partial sheet or patch at a penetration | $75 – $120 |
| Overlay skip sheathing with OSB, whole roof | $1,500 – $4,000 |
| Re-deck entire roof, all sheets (rare) | $3,500 – $8,000 |
A typical Littleton replacement needs zero to four sheets. A roof that's leaked at a valley for years, or that was roofed over and never inspected, might need eight to twelve. A hail-fractured deck after a 2-inch storm can need most of a slope.
The price per sheet includes the material, cutting out the old sheet, nailing the new one to the trusses on code spacing (6 inches at the edges, 12 in the field), and H-clips between trusses where the span calls for them. It does not include structural repair — a rotted truss chord or rafter tail under the deck is a separate line and a separate conversation.
How it shows up on the quote
The right way: a per-sheet price and an estimated count based on the inspection. "Decking replacement: $120/sheet, estimate 3 sheets, actual billed on count with photos."
The wrong way: "decking as needed," with no price, or no mention at all. That's an open line on the invoice. A quote that comes in $2,000 under everyone else's and doesn't mention decking is a quote that will find some. Our cost page lists the lines to compare.
Insurance and decking
On a hail claim, the adjuster's initial scope usually includes no decking, because they haven't seen it either. When the tear-off finds hail-fractured or water-damaged sheets, the roofer photographs them and submits a supplement with the count. Carriers generally treat hail-fractured decking as part of the storm damage, but check your policy and ask the adjuster. Water-rotted decking from an old leak is a grayer area — it's not storm damage — and it's usually on you. The hail damage page covers supplements.
Can decking be repaired without replacing the roof?
Sometimes. A single soft spot around a leaking pipe boot can be cut out and patched from above as part of a repair — strip the shingles in a 4x4 area, replace the decking, membrane, re-shingle — for $400–$800 including the boot. A soft strip along an eave can be done as part of a roof-edge repair. But if the deck is soft in three places on an 18-year-old roof, the roof is done, and putting $2,000 into patches is money that should go toward the replacement.
Decking and the next roof
The deck you put down now is the one the next two roofs will be nailed to. If you're replacing a roof after a hail claim and the adjuster's scope includes decking, take the OSB, not the cheapest option. Make sure the H-clips go in. And make sure the attic ventilation is fixed at the same time, because a deck that runs wet from condensation every January is a deck that fails again in fifteen years. Our post on ice dams covers why.
Common questions
What materials do you need to build a roof?
From the bottom up: the framing (trusses or rafters), the decking, drip edge, ice-and-water membrane at the eaves and valleys, underlayment over the rest, starter strip, shingles or metal panels, flashing at every wall and penetration, vents, and ridge cap. A replacement quote should name each of those, because the cheap quotes leave some out.
What is the inside of a roof made out of?
Under the shingles is a layer of underlayment, then the deck: OSB or plywood on most Littleton houses, 1x boards on older ones. The deck sits on wood trusses or rafters, with insulation on the attic floor below and air moving from the soffit vents to the ridge.
Should I get paid back for decking the crew didn't replace?
If the quote carried an allowance for, say, four sheets and the crew only needed two, ask how the difference is handled before you sign. A fair contract bills the actual count with photos, so an unused allowance should come off the final invoice.
How do I know if my roof decking is rotten?
From the attic, look for dark stains, flaky or delaminated wood, and rusted nail tips around penetrations and along the eaves. Press up on the deck between rafters; it should be rigid. On the roof, a spot that feels soft or bouncy underfoot is a strong sign, and a contractor will confirm it during the tear-off.
Need roof work in Littleton?
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