Free 3D deck and pergola designer
Set the footprint, height and materials, then add railings, stairs or a pergola. See your design in 3D and preview a material take-off for boards, joists, beams, posts, footings and fixings. Choose UK, Ireland, US or Canada practice and metres or feet. Costs appear only when you enter your own supplier rates. The model, checks and first quantity lines are free without sign-up; full quantities and build documents come with the paid Full Build Pack. This is a material take-off, not a structural design or supplier quote.
Deck workspace
My deck
New design4.88 m × 3.66 m · 17.8 m²
50 boards · 14 joists · 16 posts
Drawing the 3D view…
Live model
4.88 m × 3.66 m
17.8 m² · Composite (grey)
Popular in United Kingdom
Custom design4.88 m↑↓ 50 mm · shift ×10
3.66 m↑↓ 50 mm · shift ×10
0.91 m↑↓ 50 mm · shift ×10
Steps come down
Advanced shape and fixingL-shape, second level, board layout and fixing
The layout sets the waste allowance on the decking. The 3D view always draws the boards straight across.
We sell none of them. Pick on life span and upkeep.
Capped boards in grey or anthracite, the most sold UK colours. No sealing. · 25–30 years · Wash twice a year, no coating
SceneVisual only — quantities do not change
Construction sizesOptional — defaults follow United Kingdom practice
At 3.6 m you buy 50 lengths and cut off 32% of what you pay for.
3 m boards leave only 19% offcut, with a joint on each row.
- Straight boards: 5%
Boards run across the joists, square cuts at both ends. The allowance follows the layout and shape, not one flat figure. Change it under your rates if your own offcut pile says otherwise.
- Deck area
- 17.8 m²
- Decking rows
- 25
- Boards to buy (3.6 m)
- 50 incl. 5% waste
- Joists
- 14
12 more lines for your exact size, plus the cut list on real stock lengths so you buy less
Instant PDF + CSV · One payment · No subscription
- Joist span: 1.22 m between beams, within the 3 m a 47 × 150 mm joist takes at 400 mm centres.BS 8579 / TRADA span tables — 47×150 at 400 mm centres
- Frame depth: Flush beam: joists hang off the beams in 28 hangers, frame top level.
- Step rise: 6 equal steps at 152 mm, within the 190 mm limit.Approved Document K — rise up to 190 mm
- Guard: Guard needed at this height and included, 900 mm high.Approved Document K — guarding
- Post spacing: Posts at most 1.63 m apart, within the 1.8 m maximum.BS 8579 — support spacing
- Planning permission: The deck stands 914 mm above ground, over the 300 mm at which decking normally stops being permitted development. Expect a planning application, or drop the height below 300 mm.Planning Portal — decking as permitted development (300 mm)
How this is worked out
BS 8579 / Approved Document K: joists at 400 mm centres, rise up to 190 mm. Joists at 400 mm centres, posts at most 1.8 m apart, 145 mm boards with a 5 mm gap, steps at 152 mm rise, 5% waste added to the decking. A take-off, not a structural design — have it checked before you build.
Read every rule and formula we use- Height and ground
- Boards sit 914 mm above ground, so the frame stands on 16 posts in 16 footings. Keep the area under the deck clear for inspection.
- Footings and concrete
- 16 holes, 48 bags of post-set to mix. Check for drains, cables and tree roots before digging.
- Longest piece to carry in
- 3.6 m boards. Measure the side gate or the through route before ordering; if it will not go through, order shorter lengths and the cut list changes with it.
- Getting on and off
- 6 steps at 152 mm rise on 3 stringers, off the 0.91 m level.
- Edge protection
- 11.28 m of railing, 12 posts at 900 mm high.
- Ground cover
- Weed membrane 17.8 m² under the deck, laid before the frame goes down.
Build it right first time — $9
Order the right lengths, cut each piece once and square the frame before you fix it. The Full Build Pack turns this drawing into the plan you build from.
Deck build pack
Your project
Prepared with BuildPlot3D
buildplot3d.com — this band is on every free pack, above your own name.
Pay once, no account needed first. Use the email you want the job kept under; we set up your login from it after payment.
- One payment
- No subscription
- No account needed first
- PDF + CSV straight away
- Delivered immediately
How the cut list reads (example layout)
Each stock length the yard sells, with the pieces to cut from it and what is left over.
Yard order sheet · setting out · build order
98 lengths to buy · 50 deck boards · 16 posts
What $9 adds
- Full material quantities beyond the free preview
- Dimensioned framing plan and the exact cut list, packed into stock lengths
- CSV merchant order file, ready for a supplier or spreadsheet
- Setting out: the diagonal to pull so the frame is square before anything is fixed
- Yard order sheet: only things a merchant can hand over, each line checked and in your own units, with a box to tick
- Build order: each stage in sequence, with the check that goes with it
- Your company name on the PDF and the shared page, with our line gone
Building it yourself? One length cut short costs more than this pack. You get the diagonal to square the frame, the counter sheet to tick off at the yard, and the order to build in.
Quoting a customer? The same job goes out under your own name, with our line gone. Per job, no subscription to start.
Still free: the 3D drawing, the take-off on screen, a summary PDF and your own prices.
Free design record
Overall measurements, design summary and regional checks. Free, with no account.
Your prices (optional)
Timber prices change weekly and differ by yard, so we never guess them. Type one number below and you get a figure straight away.
Quick price in one number
What do you pay for composite (grey) decking, per m²? That alone gives you a figure. Add the rest of your rates below when you want the full picture.
Saved on this device. Sign in and they follow you anywhere.
Set from the board pattern and shape. Type a number to fix your own.
Save the design, overall measurements and regional checks as a PDF. The complete merchant and site files are in the paid pack.
What this deck designer gives you
- Deck boards by row and stock length, with the board gap allowed for.
- Joists, rim joists and beams at your country's usual spacing and sections.
- Posts and footings, steps with stringers, and railing with the opening at the stairs.
- Screws or hidden clips counted from the board runs.
- An open-roof pergola with its posts and rafters, if you add one.
Countries and units
Pick the UK, Ireland, the US or Canada and switch between metres and feet. Joist spacing, timber sections and board sizes follow that country's common practice, so the list matches what a local merchant or yard stocks.
Prices and what this is not
There are no built-in prices or national averages. A cost appears only when you enter your own supplier rates. The result is a planning take-off of quantities, not a structural design: check spans, footings and approvals with your local building rules or an engineer.
4.88 m × 3.66 m · Composite (grey)
17.8 m² · 98 lengths to buy (50 deck boards)