Short answer: decking is the structural wood surface your roof fastens to. Modern homes use OSB or plywood sheets. Older homes often have plank decking with gaps that modern fasteners do not hold in well. You cannot assess it until the old roof is off, which is why a per sheet price must be agreed in advance.
The three types
- OSB. Oriented strand board, the most common on homes built since the 1980s. Strong and economical. Its weakness is moisture: once saturated it swells at the edges and loses strength, and it does not fully recover.
- Plywood. Layered veneer, slightly more expensive, handles moisture better and tends to dry out rather than fail permanently. Common on older and higher end builds.
- Plank. Individual boards, found on pre 1960s homes and plenty of historic Boerne houses. Often has gaps between boards.
Why plank decking changes the job
Modern roofing fasteners are designed for continuous sheathing. Over gapped planks, a nail landing in a gap holds nothing, and it is invisible once the shingle is down. Roofing a plank deck house properly sometimes means overlaying with new sheathing first.
That is a scope and cost item that needs identifying before the contract, not discovered mid job. We cover this further in roofing historic Boerne homes.
What makes decking fail
- Long term leaks, most often around penetrations, chimneys and valleys
- Gutter overflow soaking the roof edge, which rots the eave decking and fascia together
- Attic condensation from poor ventilation, which degrades decking slowly from underneath
- Multiple layers trapping heat and moisture
- Animal damage, particularly raccoons opening up the edge
How it should be priced
Per sheet, agreed in writing before work starts. A typical estimate includes a decking allowance and a stated rate for anything beyond it. Without that, you are negotiating with your roof open.
Ask to see the bad sheets. Any contractor replacing decking should be able to show you photographs of what came out.
Signs you may have decking problems
- Sagging or wavy areas visible along the roof plane
- Soft spots underfoot, which a roofer will notice during inspection
- Daylight visible through the decking from inside the attic
- Dark staining on the underside of the sheathing
- A long running leak you have been living with
We check decking condition on every inspection as far as it can be assessed without tear-off, and we quote the per sheet rate up front. Request an inspection or call (210) 245-4125.
