Checking a Loft Conversion Quote: Exclusions, VAT, Prime Cost Sums and Deposits

The company that writes a loft quote decides what goes in it. Reading it is your job, and nobody else in the contract is paid to do that.

It matters because two loft quotes for the same house can differ in what they include. Public cost guides put a whole dormer loft at £34,500 – £75,000. Some of that spread is size and specification. Some of it is simply what each figure counts. Which?'s cost model, built on BCIS data, is unusually open about this: it includes clearing the loft and relocating the existing water tank, insulating the walls and ceiling, a new straight flight of stairs, new electrics and heating, and it leaves out internal partition walls and the final decoration. A quote can arrive as little more than a total and a page of scope written by the seller, with a short list of exclusions at the end.

So read the exclusions before the price. Then the allowances, then the VAT line and the payment terms. The headline number deserves your attention last.

What the loft company writes, and what you have to check

On a design-and-build contract there's no architect or quantity surveyor between you and the company, so checking each line against what a finished loft needs falls to you.

A shell-only price needs more work before it compares. One public cost guide puts a loft shell at £21,000 – £40,500, but every finishing trade still has to be added, and companies draw the edge of "the shell" in different places. Ask whether the stair and windows sit inside it.

The scope checklist, line by line

Work through every quote against the same list. Anything a quote doesn't mention is excluded until the company tells you otherwise in writing.

That isn't pedantry. Citizens Advice sets out when a trader can charge more than the quoted price: you ask for extra work, the trader tells you extra work is needed and you agree, or there was a genuine pricing mistake. A missing line that the regulations make compulsory lands in the second case, and you'll be agreeing its price after you've already signed.

Design and approvals. Drawings, structural calculations, the building control application and its fee, and any party wall notices. The building control body can be your council or a private approver, each with its own fees, so ask whether the fee is inside the quote or paid by you directly. Party wall costs belong on this line too if the steels or new structure cut into a wall you share, because the Party Wall etc. Act 1996 covers cutting into a party wall.

Site set-up. Scaffolding, and how many weeks of hire the price assumes. Skip and waste removal. Ask what happens if the job overruns the hire period, and get the rate for each extra week written into the quote.

Structure. Steels and how they're protected against fire, the new floor, the dormer or roof alteration, the roof windows and the stair. Where a storey is added to a two-storey house, Approved Document B Volume 1 paragraph 5.4 normally gives new floors a minimum of REI 30 fire resistance (a reduced standard is allowed for some small single-storey additions), so the floor line should say how that's achieved. The stair line should name the type and where it lands. Approved Document K paragraph 1.29 only allows an alternating tread (space-saver) stair where there's no room for a standard one and it serves one habitable room, with or without a bathroom or WC, so question any quote that prices one. Loft conversion stairs covers the rules.

Fire doors and alarms. Once a habitable room is added above the ground storey, Approved Document B Volume 1 expects smoke alarms in the circulation spaces (paragraphs 1.8 and 1.9), mains operated (paragraph 1.2). Where the new storey is high enough to trigger the escape-route rule in the next section, fire doors need pricing, or a written exclusion, along the route through the house as well as in the loft.

Electrics. New circuits for the loft and any consumer unit replacement are both notifiable under regulation 12(6A) of the Building Regulations, quoted in Approved Document P paragraph 2.5. Paragraph 3.1 allows three certification routes: a registered competent person, a registered third-party certifier, or the building control body. The quote should say which one is priced. A registered installer gives you an electrical installation certificate (paragraph 3.3), and within 30 days of finishing, the installer or its registration body issues a Building Regulations compliance certificate (paragraph 3.4).

Heating and water. Extending the heating into the loft. Moving the cold water tank, or changing the hot water system if the tank has to go. Which? builds tank relocation into its cost model, but a quote may not, so ask.

Insulation. Approved Document L Volume 1 paragraph 11.6 treats a previously unheated loft that becomes part of the heated home as a change to energy status, which brings the energy efficiency requirements into play. A quote that is silent or vague on insulation is incomplete.

Ensuite. Sanitaryware and fit-out, and above all the extract fan. Approved Document F Volume 1 paragraph 1.17 requires extract ventilation to the outside in bathrooms, and Table 1.1 sets an intermittent rate of 15 l/s. A bathroom priced without a fan ducted to outside is incomplete.

Finishes and making good. Plaster, joinery, internal doors, decoration, flooring, and making good the ceilings and walls below the new stair opening. "Basic internal finishes" means different things to different companies. Ask what yours means, room by room.