How to Estimate Decking Materials
Building a deck requires precise estimation of both the visible surface materials and the hidden structural framework. This calculator uses standard framing metrics to generate your material list.
Calculating Surface Decking
To find the linear footage of decking boards required, we convert the depth of your deck to inches and divide it by the width of a single board (accounting for a standard 1/8" to 1/4" spacing gap). This gives us the number of rows (courses) needed. We multiply the number of courses by the width of the deck to get total linear feet, then apply your waste factor for off-cuts.
Joist Spacing Rules
Joists are the structural beams that run underneath the deck boards.
- 16-inch on center (O.C.) is the industry standard for traditional wood decking.
- 12-inch on center is strongly recommended if you are using composite decking (like Trex) or installing deck boards on a 45-degree angle, to prevent sagging.
Hardware and Footings
A standard rule of thumb for deck screws is roughly 3.5 screws per square foot of deck area (assuming two screws per joist intersection). The footing calculation provides a rough estimate assuming standard load-bearing spacing (approx. one footing every 50-60 sq ft depending on beam spans), though local building codes will dictate exact footing requirements.