14x20 Deck Material List: Boards, Joists, Screws, Footings
A 14x20 deck (280 square feet) with the boards running the 20 ft way needs 33 deck boards of 20 ft, 16 joists of 14 ft and about 960 screws. With the boards running the 14 ft way instead, the same deck takes 48 boards of 16 ft, 12 joists of 20 ft and 1,032 screws. Both lists are below, and the deck materials calculator opens on this deck.
Part of the project planner: Planning and building a deck.
A 14 × 20 ft deck is 280 square feet, a large deck with room for a dining table and a separate seating group. It is the biggest list here, and the one where the framing deserves the most care.
14x20 deck material list, boards running the 20 ft way
This is the usual layout: the 20 ft side along the house, the boards parallel to it, and the joists spanning the 14 ft out from the house.
| What to buy | How much | How we worked it out |
|---|---|---|
| Deck boards, 20 ft, 5.5 in wide | 33 | 30 rows across the 14 ft width, with 10% waste |
| Joists | 16 | 14 ft long, at 16 in on center along the 20 ft side |
| Deck screws | 960 | Two per board at each joist |
| Joist hangers, up to | 32 | One per joist end hung from a ledger or rim |
| Joist tape | 224 ft | On the top of every joist |
| 80 lb bags | 26 | Footing concrete, for example 6 footings, 12 in across, 3 ft deep. Your plans set the number |
| Stain or sealer | 2 gal | One coat at about 200 sq ft a gallon (3 gal for two coats) |
Beams, posts, the ledger board and railings come from your plans and local code.
How the numbers are worked out
- Rows: the 14 ft width is 168 in. Each row takes 5.625 in (a 5.5 in board plus a 1/8 in gap), and 168 ÷ 5.625 = 29.9, so 30 rows.
- Boards: 30 rows plus 10% waste is 33.0, rounded up to 33 boards of 20 ft.
- Joists: the 20 ft side is 240 in, and 240 in ÷ 16 in = 15 spaces, which needs 16 joists.
- Screws: 30 rows × 16 joists × 2 = 960.
The same deck with the boards running the 14 ft way
Decking is not among the calculator's lengths at 14 ft, so with the boards turned to run the 14 ft way the count uses 16 ft boards, each trimmed by 2 ft, and the joists become 20 ft long and need beams under them.
| Board direction | Rows | Boards to buy | Joists | Screws |
|---|---|---|---|---|
| Boards run the 20 ft way | 30 | 33 of 20 ft | 16 of 14 ft | 960 |
| Boards run the 14 ft way | 43 | 48 of 16 ft | 12 of 20 ft | 1,032 |
In the calculator the first box, deck length, is always the way the boards run, so swap the two numbers to see the other layout.
Which board length to buy
The 14 ft width takes 30 rows, 4 more than a 12 ft wide deck. In 20 ft boards that is 33 boards with no joints, in 16 ft boards 42 and in 12 ft boards 55, each of the shorter lengths with a joint in every row.
| Board length (boards run the 20 ft way) | Boards to buy | Joints |
|---|---|---|
| 8 ft boards | 83 | A joint in every row |
| 10 ft boards | 66 | A joint in every row |
| 12 ft boards | 55 | A joint in every row |
| 16 ft boards | 42 | A joint in every row |
| 20 ft boards | 33 | None: one board is one row |
With narrower 2x4 boards (3.5 in) this deck takes 52 boards of 20 ft, and with wide 2x8 boards (7.25 in) it takes 26.
Joists and screws by spacing
The 16 joists are 14 ft long. That is a long span: look up the joist size for 14 ft in the span table for your lumber, or plan a beam part-way so that each span is shorter.
| Joist spacing | Joists, boards the 20 ft way | Screws | Joists, boards the 14 ft way | Screws |
|---|---|---|---|---|
| 12 in | 21 | 1,260 | 15 | 1,290 |
| 16 in | 16 | 960 | 12 | 1,032 |
| 24 in | 11 | 660 | 8 | 688 |
Footing concrete by number of footings
The number of footings comes from your plans, so the list above uses 6 only as an example. For footings 12 in across and 3 ft deep, with 10% extra:
| Footings in your plans | 80 lb bags of concrete |
|---|---|
| 4 footings | 18 |
| 6 footings | 26 |
| 8 footings | 35 |
| 9 footings | 39 |
| 12 footings | 52 |
Checks before you start
- A deck this size is very likely to need a permit and stamped or pre-approved plans: ask before you price the lumber.
- Get a permit and find out the frost depth for your footings.
- Size the joists for the 14 ft span from the span tables for your lumber.
- Use hot-dip galvanized or stainless fixings for treated lumber.
Other sizes: 8x8 deck, 10x12 deck, 12x12 deck, 12x16 deck, 12x20 deck, 16x16 deck. See also the materials list for a deck and how many deck boards you need. These are estimates for planning.
Frequently asked questions
How many deck boards for a 14x20 deck?
33 boards of 20 ft when the boards run the 20 ft way (30 rows across the 14 ft width, with 10% waste). If the boards run the 14 ft way it is 48 boards of 16 ft in 43 rows.
How many joists for a 14x20 deck?
16 joists of 14 ft at 16 inches on center when the boards run the 20 ft way, or 12 joists of 20 ft when the boards run the 14 ft way. The span table for your lumber decides the joist size and whether a beam is needed.
How many screws for a 14x20 deck?
About 960: 30 rows × 16 joists × 2 screws. With the boards the other way it is about 1,032.
How many square feet is a 14x20 deck?
280 square feet (14 × 20). One coat of stain at about 200 square feet a gallon takes 2 gallons for the surface, and two coats 3.
How much concrete for the footings of a 14x20 deck?
It depends on the number of footings in your plans. As an example, 6 footings 12 inches across and 3 feet deep take about 26 bags of 80 lb mix. Your frost depth and plans set the real size and number.
More guides
Tools & materials for this project
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.
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