In short
- A dock decking calculator turns the dock size and board choice into rows, linear feet, boards, joists and an approximate pile count.
- Boards are laid with a small gap, commonly 1/8 to 1/4 in. A 6 in nominal board is about 5.5 in wide; a 4 in nominal board about 3.5 in.
- Joists are commonly 16 or 24 in on center. Composite boards often need 16 in or less, so follow the board maker.
- A 40 x 6 ft dock is about 36 boards at 16 ft with 10% waste. Cape Coral docks need a city permit and have rules on projection into the canal: check the city’s dock rules.
On this page
This dock decking calculator is for Cape Coral canal-front owners who want to know how many boards, joists and piles a dock takes before they ask a dock builder for a quote. It uses quantities only, with no prices. It supports our Cape Coral dock and boat lift permit checklist.
En español: calculadora de materiales para muelle en Cape Coral
| Your numbers | Result |
|---|
By section
| Section | Rows | Lin ft |
|---|
Example: 40 x 6 ft dock, no finger, 5.5 in boards, 3/16 in gap, joists 16 in on center, 16 ft boards, 10% waste.
How the quantities are worked out
- Area.
Length times width. A 40 x 6 ft dock is 240 sq ft.
- Board rows.
Width in inches divided by board width plus gap, rounded up. 72 / (5.5 + 0.1875) = 12.7, so 13 rows.
- Linear feet and boards.
13 rows x 40 ft = 520 linear ft. Add 10% waste (572) and divide by 16 ft: 35.75, so 36 boards.
- Joists.
Length x 12 / spacing, plus one: 480 / 16 + 1 = 31 joists, each as long as the 6 ft width, so 186 linear ft.
- Piles.
One row along the open edge: 40 / 9 ft + 1 = 5.4, so about 5 to 6. This is a typical planning figure; an engineer decides.
Boards and joists for common dock sizes
| Size | Area | Boards | Joists |
|---|---|---|---|
| 20 x 4 ft | 80 sq ft | 13 | 16 |
| 30 x 5 ft | 150 sq ft | 23 | 23 |
| 40 x 6 ft | 240 sq ft | 36 | 31 |
| 60 x 6 ft | 360 sq ft | 54 | 46 |
These use 5.5 in boards, 3/16 in gaps, 16 ft boards, 10% waste and joists 16 in on center, with no finger. Your design may differ.
Permit and canal rules come first
Size is not only your choice. A Cape Coral dock needs a city permit, and there are limits on how far a dock can project into the canal. Try our dock projection vs canal width calculator to see the 25% limit for your canal, check the city’s dock rules, and ask your dock builder what the permit drawings will show. Our dock and boat lift permit checklist covers the papers the city lists, the state and federal approvals, and the survey.
Planning a lift too? The boat lift capacity calculator sizes the lift from your boat’s loaded weight. If the wall itself is old, read about seawall permits in Cape Coral first, because dock work next to a failing wall can cause trouble later.
Wood or composite: what changes the count
| Item | Typical | What to know |
|---|---|---|
| Board width | 5.5 in, 3.5 in | A "6 in" board is about 5.5 in wide; a "4 in" board about 3.5 in. |
| Gap | 1/8 - 1/4 in | Set by the board maker and how the material swells. |
| Joist spacing | 16 or 24 in | Composite often needs 16 in or less. Diagonal boards need closer spacing. |
| Piles | 8-10 ft | Planning figure only; depends on design and soil. |
Questions to ask your dock builder
- Which board and which joist spacing? Ask for the maker’s installation instructions.
- How many piles, and how deep? The count comes from the engineered design.
- Who pulls the permit and handles state and federal approvals?
- How much waste is in the board count? Compare with the 5 to 15% used here.
Next step: get a written quote
This tool estimates materials, not the price or the job. We are a referral service, not a dock builder; we connect visitors with independent local providers. Use the form below to ask independent local contractors for a written quote, and read how to choose a seawall contractor first.
Sources
- Trex: how to install deck joists: 16 in on center maximum for residential composite decking.
- City of Cape Coral: New Wood Dock Guideline, Residential: read it for projection and setback limits.
Frequently asked questions
How many deck boards do I need for a dock?
Divide the dock width by the board width plus the gap to get the number of rows, round up, then multiply by the dock length for the linear feet of decking. Divide by the board length and add waste. A 40 x 6 ft dock with 5.5 in boards and 3/16 in gaps is 13 rows and 520 linear feet, or about 36 boards at 16 ft with 10% waste.
How far apart should dock joists be?
Sixteen or 24 inches on center are the usual choices for wood decking, depending on the board and the framing. Composite makers commonly require 16 inches or less, and some suggest closer spacing in hot climates or for diagonal layouts. Follow the board maker's instructions and your dock designer's plan.
How many piles does a dock need?
Piles are commonly spaced somewhere around 8 to 10 feet along a dock, which is the planning figure used here. The real count and spacing depend on the design, soils, loads and the permit drawings, and an engineer or the dock designer decides.
Do I need a permit to build or replace a dock in Cape Coral?
Plan on one. The City of Cape Coral publishes dock guidelines, and state or federal approval can also apply. Check the city's dock rules, including how far a dock may project into the canal, before you design anything. Our permit checklist lists what the city asks for.