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What it costs to put a roof over an existing deck — and what the deck needs first.
With these inputs:
| Result | Value |
|---|---|
| Estimated roof cost | $5,867 – $10,487 |
| Per square foot of deck | $31 – $55 |
| Roof plan area | 207 sq ft |
| Style | Shed roof |
| Structure — posts, beams, rafters | $4,147 – $6,636 |
| Roofing and underlayment | $829 – $1,452 |
| 2 new footings and post | $640 – $1,500 |
| Flashing, permit and sundries | $250 – $900 |
A roof is dead load the deck carries every day of the year, plus snow load in winter — which is exactly the load an open deck never sees. Before pricing the roof, get the existing frame checked: the beam and posts under the roof line usually need upsizing, and the roof posts normally want their own footings rather than bearing on the deck. Attaching to the house also means a second ledger and a flashing detail into the existing roof, which is where covered decks leak. Figures are national estimates; a structural drawing is commonly required for the permit.
Roofing a deck changes it from a summer surface into a room you use nine months a year. It also adds permanent dead load the original frame may never have been sized for. This prices the roof by size and style, splits out the posts and footing upgrades most covers need, and flags the structural checks that come before any of it.
For a 16 by 12 ft deck, an aluminium patio cover kit runs roughly $4,500 to $8,500 installed, a framed shed roof with shingles about $6,500 to $12,000, and a gable roof matching the house $8,500 to $16,000. Adding a finished tongue-and-groove ceiling is another $1,200 to $2,100 on that size, and dedicated footings for the roof posts add $320 to $750 each.
Often not as built. An open deck is framed for 40 pounds per square foot of live load and 10 of dead; a roof adds permanent dead load plus the winter snow load the deck was never designed to hold, all concentrated at the posts. The usual fix is dedicated roof posts carried on their own footings beside the deck frame rather than on it. Have it looked at before you buy anything.
Yes, typically 30 to 45 percent less, because an aluminium kit arrives pre-engineered and goes up in a day or two. The trade-offs are appearance and resale — a framed roof with matching shingles reads as part of the house, an aluminium cover reads as an add-on. If the deck is visible from the street, that difference matters more than the price.
Nearly always, even where the deck itself did not need one. A roof changes the structure's load path and its footprint, and it usually ties into the house's own roof, so building departments want a plan showing the beam, post and footing sizes. Many also require a snow load calculation. Budget for drawings as well as the permit fee.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.