A straight answer starts in the attic
One layer, sometimes. Two layers, never.
We will go over one layer of shingles only after we walk the roof and inspect the deck from inside the attic. We do not roof over two layers.
How a roof-over works.
For an exposed-fastener roof, we install 1x4 wood strapping every 24 inches and screw it through to the rafters. The panels go over the strapping, giving the new roof a straight, solid fastening surface.
For standing seam, we tear off nearly every time. Shingle edges can show through a flat panel, and the hidden clips need a flat deck.
When the old roof has to come off.
- Two shingle layers already in place
- Soft spots or rot in the roof deck
- Wood shakes below the shingles
- A leak that has been running for a while
- Ice-dam damage at the eaves
- Attic ventilation that needs to be fixed
We show both prices when both are possible.
Going over can save about $1.50 to $2.50 per square foot in tear-off and dump fees, plus about a day. The tradeoff is simple: nobody sees that deck again until the next roof. When both work, your estimate shows both options side by side with attic photos.
