Which tool fits the job
For a new fence, start with the wood fence planner: it prices everything and draws the fence to scale; the fence calculator only counts posts and pickets. For new boards or a re-stain on an existing deck, use the deck resurfacing planner; the deck boards calculator counts boards and screws alone; the deck stain calculator gives gallons of stain. The stair calculator turns a rise into risers, treads and stringer length.
Plan in this order
Fix the heights, then the spacing (posts usually 8 ft apart, joists 16 in), then count boards. A 9 ft (108 in) rise needs 14 risers of about 7.71 in and 13 treads.
Common buying mistakes
- Buying linear feet instead of pieces. Boards come by the piece: a 12 × 16 ft deck with 5½ in boards needs 26 rows, or 29 boards 16 ft long with 10% extra.
- Too few posts. A fence needs one post more than it has sections, plus one for each corner and gate.
- Uneven steps. The code allows risers up to 7¾ in and treads from 10 in, with no more than ⅜ in between the tallest and shortest riser, so measure to the finished landing. Four or more risers need a handrail.
- Joists too far apart. 5/4 wood decking may span joists up to 16 in apart, 12 in when laid diagonally; composite boards follow the maker’s span table.
- Posts not rated for the ground. Buried wood must be treated for ground contact.
Call 811 a few days before you dig post holes so buried utilities get marked, and check permits and the property line first. Deck frames and stair stringers carry people: have a deck builder or your building department check a soft frame or a new build.