What should you know about putting a roof over an existing deck?
Short answer. A roof over an existing deck usually needs new or upgraded footings and posts, because most deck foundations were sized only for the deck. You will also need a permit, a pitch that suits the roofing material, and careful flashing where the new roof ties into your house or existing roof.
Can your deck carry it?
A roof adds weight from framing, decking and shingles, plus wind uplift and the loads codes require roofs to carry. That load arrives at a few posts, so the footings under those posts often must be larger and deeper than a typical deck footing. Many builders install new posts and footings for the roof rather than relying on deck posts. A designer or engineer can size them.
Attaching to the house
- Ledger on the wall: for a shed roof, a ledger bolted to the house framing with proper flashing above it.
- Tie into the existing roof: for a gable or hip, the new roof meets the main roof and needs valley flashing, step flashing and sometimes a cricket. This joint is where most porch roofs leak.
Pitch and materials
- Asphalt shingles need at least 2/12, with double underlayment below 4/12.
- Lower pitches need metal panels rated for low slope or a membrane.
- Gutters should carry water away from the deck and the house.
Permits in Georgia
Covered decks and porches almost always require a building permit, and rules vary by city and county. HOAs typically want plans too. See roofing permits in Georgia and HOA roof approval.
If your main roof is near replacement, consider doing both together so the shingles match and the tie-in is flashed with new materials; roof flashing explained covers the details.