How to choose a decking installer and read a decking quote

In shortGet three itemised quotes against one written specification, check each firm exists at Companies House or on a trade register, and ask for public liability insurance and a written workmanship guarantee before you pay a deposit. A proper decking quote names the board, the joist treatment class and centres, the fixings, the balustrade height, VAT and the payment stages. Installer schemes such as Millboard Approved Installer, TrustMark, BALI and APL prove that a firm has been vetted or trained, not that your deck will be good, so look at finished work too.

Most decks in Britain are fitted by small firms: a landscaper with two vans, a joiner who does gardens in summer, a father and son who have built a hundred of them. Few are bad. The trouble is that a deck hides its weaknesses under the boards, so the difference between a good installer and a poor one may not show for five years, when the joists go soft. Choosing well at the start is the only protection you have.

Finding firms

Three routes work. The first is a recommendation from someone whose deck you have stood on. The second is a trade register: Millboard publishes a searchable list of its approved installers, and TrustMark, BALI, the APL, the Federation of Master Builders and the Guild of Master Craftsmen each have a public member search. The third is a directory like this one, which gathers the firms that appear for decking in a town and checks their websites.

Whichever route you use, prefer firms that fit decks regularly over general builders who will do one. Composite has rules on joist centres, expansion gaps and fixings that a first-timer will not know, and the board warranty depends on them. Our town pages, for example Sheffield, Glasgow and Cardiff, show which firms name a decking service and which boards they mention.

What a directory can check, and what it cannot

This directory checks each firm’s own website every week: that it answers, that its pages describe a decking service and name the boards it fits, which towns it covers, and which installer schemes or trade bodies it claims. A scheme is marked confirmed only once we have found the firm on the scheme’s public register. That is the full extent of it. We have not seen any firm’s work, we hold no reviews, and prices, guarantees and years trading are shown as the firm states them. The rest is yours to check.

Questions to ask before a quote

• Who will be on site, and have they fitted this board before?
• What treatment class will the joists and posts be? The right answer at or near the ground is Use Class 4, not “treated” without a class.
• What joist centres will you use, and do they match the board maker’s guide?
• How will the posts be fixed: concrete, pads or adjustable pedestals?
• Will there be a weed membrane and gravel, and how will air get under the deck?
• Does the height need planning permission, and who checks? Our planning guide has the limits.
• Can I see two finished decks, one from this year and one at least three years old?

The last question matters most. A deck at three years shows whether the frame was built properly. A photograph of a new one shows nothing.

What a proper decking quote itemises

A decking quote should be a specification with prices against it, not a single figure:

If a quote has none of this, ask for it. A firm that cannot write down the joist treatment class has not thought about it, and the deck will be built from whatever the merchant has in stock.

Schemes and memberships, and what they prove

Badges prove different things, and it pays to know which.

Manufacturer schemes. Millboard’s Approved Installer programme involves training at the maker’s academy and completed installations, and Millboard lists approved firms on a public page, so the claim can be checked. Trex runs a TrexPro programme in the UK; Composite Prime runs an installation course; Ecodek and Cladco publish installation guides rather than installer lists. A manufacturer badge says a firm has been trained on that board. It does not say the firm is insured, solvent or good at groundwork.

Trade bodies. BALI vets Registered Contractors with site inspections, references and insurance checks, and belongs to an ombudsman scheme. The APL inspects members’ completed work and offers a deposit guarantee on some contracts. The Federation of Master Builders inspects members and offers dispute resolution. TrustMark is the government-endorsed scheme, with a public register. Membership means the firm has passed vetting and agreed to a code; the dispute routes are worth more than the badge.

Marketplace membership. Paid directories vet identity and insurance and carry reviews. They prove the firm paid for a listing and passed the entry checks; weight the older, detailed reviews.

No badge at all. Plenty of excellent small firms belong to nothing, because membership costs money and they have work enough. The absence of a badge is not a warning sign. A badge you cannot find on the scheme’s own register is.

Insurance, deposits and payment

Ask for the public liability insurance certificate and check the dates and the limit; £2 million to £5 million of cover is typical for a landscaping firm. A firm that employs anyone must also hold employer’s liability insurance. Check a limited company at Companies House, free, for its age and whether accounts are filed.

A modest deposit to secure the date and order materials is normal. Composite boards are often ordered to the job, so a larger materials payment on delivery is reasonable; paying for the whole job up front is not. Agree stages in writing: deposit, materials on site, frame complete, final payment when the deck is finished and you have walked it. Pay by bank transfer or card, never cash for a discount, and keep the quote and every message.

The written guarantee

Two guarantees apply to a deck. The board warranty comes from the maker and runs for the period in its document, typically 25 years for premium capped brands, provided the board was fitted to the maker’s guide. The workmanship guarantee comes from the installer and covers the frame and the fitting. Ask for the period in writing on the quote. A firm that offers one year on a structure it expects to last twenty is telling you something, and a guarantee is only as good as the firm’s continued existence.

Red flags

• A price with no specification, or a specification with no treatment class.
• Pressure to sign on the day, or a discount that expires tonight.
• Cash only, or a large payment before any material arrives.
• No fixed address and a website with no company details.
• Badges that do not appear on the scheme’s register.
• “No need for planning” for a deck that will clearly be high at one end.
• No mention of a weed membrane, ventilation or the damp-proof course.

How to compare three quotes

Write one specification first, even a short one: size, height, the board (or “composite, capped, mid-grey”), steps, balustrade, lighting, removal of the old deck. Send the same sheet to three firms and ask each to quote against it line by line. Then compare the lines, not the totals. If one firm is far cheaper, find the line that explains it: usually the subframe, the board or VAT. If you cannot find it, the saving is coming from something that was not written down. The cost guide gives the ranges to measure each quote against, and composite or timber helps you fix the specification first.

When you are ready for quotes, the town pages list installers whose websites we check: all towns.