A deck cost estimator helps you answer the most important question before you build: what will this deck actually cost? You enter your deck’s size, the materials you want (pressure-treated timber, cedar or composite), and any extras like railings, steps or lighting, and get a realistic budget breakdown — materials, labour if you’re hiring help, and the little extras that catch people out.
Decking costs vary wildly — a small softwood platform might run a few hundred pounds or dollars, while a large multi-level composite deck with railings and lighting can run into five figures. Knowing a realistic figure before you buy a single board stops two classic mistakes: starting a project you can’t afford to finish, and massively over-budgeting and never getting started at all.
This estimator is built for DIYers planning their own build and for anyone getting quotes from contractors — if you know roughly what the job should cost, you can spot a quote that’s suspiciously cheap or wildly inflated. Pair it with our detailed breakdown in how much does it cost to build a deck for a deeper look at where the money goes.
How to Use the Deck Cost Estimator
- Enter your deck dimensions. Measure the length and width of the area in feet or metres. For L-shaped or multi-level decks, calculate each rectangle separately and add them — the estimator accepts a total square footage.
- Choose your decking material. Select pressure-treated softwood (cheapest), cedar or redwood (mid-range, naturally rot-resistant), or composite (priciest up front, lowest maintenance). The estimator applies typical per-square-foot material rates for each.
- Add railings and balustrades. If any edge of the deck is more than 30 inches (about 76 cm) off the ground, you’ll likely need railings by code — and most people want them anyway. Enter the linear footage of railing needed.
- Include steps and extras. Add the number of steps, plus extras like built-in benches, lighting, skirting to hide the subframe, or a pergola. Each adds a typical cost range.
- Choose DIY or hired labour. Select whether you’re building it yourself or hiring a contractor. Labour typically adds 40–60% on top of material costs in the US and UK, and the estimator applies a typical multiplier.
- Review the breakdown and adjust. You’ll see materials, labour, and extras itemised with low–high ranges. Change the material or drop an extra to see how the total responds, then budget for the high end of the range.
How the Calculation Works
The estimator starts with your deck area in square feet (or converts from square metres). It multiplies that by a typical installed material rate per square foot for your chosen material: pressure-treated timber roughly £8–12 / $10–15 per sq ft for materials alone; cedar roughly £12–18 / $15–22; composite roughly £18–30 / $25–35. These rates cover deck boards, joists, posts, bearers and fixings — the full subframe, not just the visible boards.
Railings are priced per linear foot (typically £25–45 / $30–60 per ft installed, less for DIY), steps at a typical £80–150 / $100–200 per step, and extras like lighting or skirting get flat typical allowances. If you select hired labour, the estimator multiplies the material total by a typical labour factor (around 1.5×) rather than guessing hours, since rates vary so much by region.
Worked example: A 16 × 12 ft deck (192 sq ft) in pressure-treated timber, DIY build, with 30 ft of railing and 3 steps. Materials: 192 × £10 ≈ £1,920 (mid-range). Railing: 30 × £15 ≈ £450 for DIY materials. Steps: 3 × £60 ≈ £180. Total ≈ £2,550, and budgeting the high end of the range gives roughly £2,800–3,000 all in. The same deck in composite with hired labour would typically land around £6,000–8,000.
Tips for Accurate Results
- Measure the real footprint, including overhang. Decks often extend slightly beyond the subframe — measure the finished size you want, not just the ground area.
- Price materials locally before committing. Timber prices swing with the market and vary a lot between suppliers. Get two or three quotes and use the estimator’s ranges as a sanity check.
- Don’t forget the subframe. Joists, posts, concrete footings, brackets and screws can be 30–40% of the material cost. The estimator includes them, but contractor quotes sometimes list them separately — compare like with like.
- Budget for the high end. Ground preparation (levelling, weed membrane, drainage), delivery charges and fixings always add up. Add 10–15% contingency on top of the estimate.
- Check permits and codes first. Many areas require a permit for raised decks, and railings, stair dimensions and footing depths are regulated. A deck that fails inspection costs far more than a permit fee.
- Factor in maintenance. Timber decks need cleaning and re-staining every 2–3 years — real money over a decade. Composite costs more now but far less later; the estimator notes this trade-off.
Frequently Asked Questions
How much does it cost to build a deck per square foot?
As a rough guide: pressure-treated timber £8–15 / $10–20 per sq ft, cedar £12–22 / $15–28, composite £18–35 / $25–45 — these are typical DIY material costs. Hiring a contractor roughly doubles the total. Your region, deck height and extras move the figure up or down.
Is it cheaper to build a deck yourself or hire someone?
DIY typically saves 40–60% of the total cost since you’re only paying for materials. But be honest about your skills: a deck is a structural project, and mistakes in footings or joist spans are expensive to fix. A hybrid approach — DIY the build, hire help for footings — works well for many.
What is the cheapest decking material?
Pressure-treated softwood is the cheapest upfront by a clear margin. It needs regular maintenance (cleaning and staining every 2–3 years), so over 15–20 years the total cost narrows against composite — but for a low initial outlay, nothing beats it.
Do I need planning permission or a permit for a deck?
It depends on height and location. In the UK, raised decks over 30 cm often need planning permission; in the US, most municipalities require a permit for decks above 30 inches or attached to the house. Always check with your local authority before buying materials.
How long does a deck last?
A well-built, well-maintained timber deck typically lasts 10–15 years; cedar a bit longer at 15–20. Composite decks commonly carry 25-year warranties and can last 25–30 years. Good drainage and airflow under the deck matter as much as the material choice.
If your garden project includes boundaries as well as decking, our guide to building a garden fence: materials and cost helps you budget the fencing side with the same approach.