Decking cost: what decides the price of a new deck

Why decking cost per m2 is only a rough guide

Online calculators work out a figure by multiplying the area by a rate. That is fine for a first idea, but it assumes a flat, open, easy to reach garden and a simple rectangle. Real gardens slope, have manhole covers to work around, sit behind terraced houses with no side access and want steps down to the lawn. Each of those adds time that a rate per square metre cannot see.

Small decks also cost more per square metre than large ones. Setting out, levelling and finishing edges take a similar amount of time whether the deck is six square metres or twelve, so the fixed part of the job is spread over less area.

Board choice: softwood, hardwood and composite

Pressure treated softwood is the most affordable board and is what most garden decks in the UK are built from. It needs cleaning and treating every year or two to stay in good condition. Hardwood boards last longer and look richer but cost more and are harder to cut and fix. Composite boards, made from wood fibre and plastic, cost the most to buy, need little upkeep and do not splinter, though they need closer joist spacing and specific fixings.

• Softwood: lowest material cost, regular maintenance
• Hardwood: higher cost, long life, harder to work
• Composite: highest material cost, low upkeep, stricter frame rules
• Grooved or smooth faces, and hidden or face fixings, also change the price

The frame underneath

The sub frame is the part nobody sees and the part that decides how long the deck lasts. Joists sit on bearers, which sit on posts or pads. A low deck on flat ground can sit on pads with a weed membrane beneath. A raised deck over a slope needs posts set in concrete, more timber and more time, and the higher it gets the more bracing it needs. Joist spacing is closer for composite boards, which adds timber.

Any deck where the walking surface is more than 300mm above the ground counts as a raised platform and normally needs planning permission in England, so most garden decks are kept below that height. Check with your council if your design needs to be higher.

Ground, access and old surfaces

If the area is overgrown, a clearance comes first. If there is an old patio or rotten deck in the way, removing it and getting rid of the waste is part of the cost. Ground that slopes steeply needs more digging and longer posts. Access matters too: when every board has to come through the house, it is slower than carrying it down a side path, and the quote reflects that.

Extras that add to the price

Steps, fascia boards around the edge, balustrades or handrails, built in planters, lighting cut outs and curved or angled shapes all add materials and labour. A balustrade is often needed where a deck is raised beside a drop. None of these are wrong to want; they just need to be in the quote so you are comparing like with like.

How to compare decking quotes

Ask each quote to state the board type and make, the joist size and spacing, how the frame is supported, how the ground underneath is treated, and whether steps, fascias and waste removal are included. A cheaper quote with wider joist spacing or no membrane is not the same deck. A clear written quote that lists these things is easier to judge than a single figure.

If you are not yet sure decking is the right choice, the decking vs patio guide compares the two. If you already have a deck that has gone soft or loose, the decking repair guide explains when repair is worth it.

Need it sorted? Book decking installation

CRF builds decks for modest gardens around Rochester and Medway. See decking installation for how the work is carried out, then send photos of the area, rough measurements and the board you like through the contact page for a written quote.

Frequently asked questions

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