Building a deck in the UK? Enter the size in metres and pick your boards. You get the deck boards, joists and noggins to buy, with extra for cuts included.
Your shopping list
27Deck boards to buy
11Joists
10Noggins
- Deck area12 m²
- Rows of boards21
A 5 mm gap is left between boards. Check your board maker for joist centres. Extra of 10% is included.
How to use the UK Decking Calculator with Noggins
- Enter the deck length and width in metres.
- Pick the board width and length, and the joist centres in millimetres.
- Choose how many rows of noggins your plan needs and read your list.
The math behind it
Rows of boards = deck width / (board width + 5 mm gap), rounded up
Joists = deck length / joist centres + 1, rounded up
Noggins = rows of noggins x (joists – 1)
A worked example
What we typed in
- Deck length: 19.69 ft
- Deck width: 13.12 ft
- Board width: 5.5 in wide (140 mm)
- Board length: 11.8 ft
- Joist centres: 15.7 in apart (400 mm)
- Rows of noggins: 2 rows
- Extra for mistakes and cuts: 10%
What we got
- Deck boards to buy: 52
- Joists: 16
- Noggins: 30
- Deck area: 258.33 sq ft
- Rows of boards: 28
Tips from the job site
- 400 mm joist centres are typical for timber. Composite often needs 300 to 350 mm.
- Keep a gap under the deck so air can flow and the timber can dry.
Common questions
How many deck boards do I need for a 4 x 3 m deck?
With 140 mm boards, 3.6 m lengths and 10% extra you need about 27 boards.
What are noggins on a deck?
Noggins are short pieces fixed between joists to stop them twisting and to support board ends.
See all Deck Calculators.
Last checked: (worked example and form display).