Getting quotes for a loft conversion is where many homeowners start to feel out of their depth. The numbers are large, the scope is technical, and it is easy to compare quotes that are not actually covering the same work. A low quote is not a bargain if it excludes structural engineering, Building Regulations fees, scaffolding, or a staircase.

This guide explains what a complete loft conversion quote must include, what the warning signs look like, and how to run a fair comparison before you commit.

What a Full Loft Conversion Quote Should Include

A properly scoped quote will itemise everything required to take the project from ground level to Completion Certificate. If any of the following are absent, ask explicitly whether they are included or excluded, and get the answer in writing.

Structural and Design Elements

Structural Build

  • Temporary weatherproofing during roof opening
  • Structural steelwork (typically £1,500–£4,000 for a standard dormer)
  • Steel delivery and craneage or manual handling
  • New floor structure (156 mm or 200 mm joists, decking)
  • Dormer or hip-to-gable framing
  • Roof covering (tiles, felt, battens to match existing)
  • Dormer cladding (zinc, lead, timber, or render)
  • Roof windows or dormer windows, installed and weathertight

Access and Scaffolding

  • Scaffold erection, weekly hire, and strike (commonly £2,000–£4,500 for a standard loft)
  • Skip hire and waste removal

First and Second Fix

  • Staircase supply and installation (typically £2,000–£5,000)
  • Insulation (warm roof and floor; 100–150 mm rigid insulation between rafters)
  • First-fix carpentry (stud partitions, door linings)
  • First-fix electrics (circuits, consumer unit work if needed)
  • First-fix plumbing (if bathroom included)
  • Plasterboard and skim plastering
  • Second-fix electrics (sockets, lighting, extractor)
  • Second-fix plumbing and bathroom suite (if included)
  • Joinery (skirting, architrave, internal doors)
  • Decoration (two coats on walls and ceilings; primer on woodwork)

Items Often Omitted from “Budget” Quotes

  • Floor finish (engineered timber, carpet, LVT)
  • Loft hatch or loft ladder for any retained storage
  • Smoke and heat detection (Part B calls for a mains-powered alarm system wherever a new habitable room is added above the ground storey)3
  • Fire doors to escape route (Part B, where the conversion creates a storey more than 4.5 m above ground level)3
  • Mains-wired smoke alarms on each floor (often omitted from initial scope)

Sample Quote Breakdown: Rear Dormer with En-Suite (London/SE, 2026)

The following illustrates a realistic itemised quote for a typical rear dormer conversion on a 1930s semi-detached house in greater London, adding one bedroom with en-suite shower room.

ItemTypical range
Structural engineer£700–£1,100
Architectural drawings + Building Regulations£1,200–£2,000
Building Regulations application fee£450–£650
Scaffold (erect, hire 10 weeks, strike)£2,500–£4,000
Temporary weatherproofing£400–£700
Structural steelwork (supply + install)£2,000–£3,500
New floor structure£1,500–£2,500
Dormer frame, roof covering, cladding£6,000–£10,000
Roof windows or dormer windows£1,500–£3,000
Staircase (supply + install)£2,500–£4,500
Insulation£2,000–£3,500
First and second fix (carpentry, elec, plumbing)£8,000–£14,000
Bathroom suite + tiling£3,500–£6,000
Plastering£2,500–£4,000
Decoration£2,000–£3,500
Floor finish£1,200–£2,500
Waste removal£600–£1,000
Total£38,550–£66,450

A mid-spec project in London would typically come in at £48,000–£56,000 all-in for the scope above. If a quote comes in significantly below £40,000 for a dormer with en-suite in London, something has been excluded.

Red Flags in a Loft Conversion Quote

Vague Lump Sums

“Complete loft conversion, £32,000” tells you nothing about what is and is not included. Any reputable contractor will itemise. If they will not, you have no basis for comparing with other quotes and no protection if items are claimed to be “extras” later.

No Mention of Building Regulations or Structural Engineering

These are not optional, all habitable loft conversions require Building Regulations approval and structural engineer’s calculations. A quote that makes no mention of either is either excluding them (leaving you to source and pay separately) or not accounting for them at all.

Excessive Upfront Payment Request

A reasonable deposit for a loft conversion is 10–20% of the contract value, paid on commencement. Some contractors ask for 25% upfront for material procurement, which can be acceptable if materials are unusual or lead times long. Any request for 30% or more before work starts, or for staged payments that do not correlate to measurable completion milestones, is a risk. Rogue traders in the construction sector routinely request large upfront sums and disappear or slow down dramatically after receipt.

No Specification of Materials

“Tile the dormer”, with what? Zinc? Lead? Tile? Cedral? Specification matters both for cost and building control approval. A quote should state the proposed cladding material and the roofing tile specification.

No Mention of Party Wall

If the loft abuts a party wall (essentially certain on a terraced house and common on semis), the Party Wall etc. Act 1996 requires a party structure notice to be served on the neighbour at least two months before the work begins.4 A contractor who makes no mention of this has either not assessed the project properly or is planning to skip it, both are problems.

Questions to Ask Every Contractor

  1. Is Building Regulations approval included in your quote, and who submits?
  2. Who is the structural engineer, and are their calculations included?
  3. What is your scaffold specification and how long does it include for hire?
  4. What tile/cladding specification are you pricing for the dormer?
  5. Does your quote include all fire doors and smoke alarms required under Part B?
  6. What are your proposed payment stages, and what completion milestone triggers each payment?
  7. Do you carry public liability insurance of at least £2 million, and are you registered under a competent person scheme (e.g., NAPIT or NICEIC for electrics)?5
  8. Will you provide a written contract before work starts?

How to Compare Quotes Fairly

Lay the quotes side by side and tick off each item in the list above. Where one quote includes something another excludes, adjust the total by adding the missing item’s typical cost. Only compare like-for-like totals.

Do not automatically choose the lowest quote. The difference between a £42,000 quote and a £52,000 quote is often partially explained by items missing from the lower one and partially by genuine differences in contractor overhead or margin. Once you have normalised for scope, the gap usually narrows. If two quotes are genuinely equivalent in scope and one is 15–20% cheaper, ask the cheaper contractor to explain where the saving comes from, the answer will tell you a great deal.

Check references. Ask for the addresses of two or three recently completed loft conversions and view them in person if possible. Ask the homeowners whether the contractor finished on time, how they handled problems, and whether they would use them again.

A written contract, ideally using a standard form such as the JCT Building Contract and Consultancy Agreement for a Home Owner/Occupier or a reputable contractor’s own terms, should be in place before any work starts or any money changes hands beyond the deposit.6

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.

References (6)

Figures in this note were checked against the sources below on 9 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

  1. 1coststrong locallyBelfast City Council.RN-KIELJ1A price, true at 2026-04. the building control fees Belfast City Council charges, which is the statutory fee scale for building regulations applications in that district. Northern Ireland sets its building control fees locally, so this is one council's scale rather than a national one
  2. 2costsupplier figureSurvey of Party Wall.RN-JLADBQA price, true at 2026-09. a London party wall surveying practice publishing its own fixed fee, £950 to £1,450 per adjoining owner for a standard extension, broken into the stages it covers: site appraisal, serving the statutory notices, tracking the 14 day response, the schedule of condition, negotiating access, drafting the award and delivery, with VAT added on top. It is also the source for the point the notes most often get wrong, that the fee is per ADJOINING OWNER rather than per job, and that a neighbour who dissents and appoints their own surveyor is paid separately again by the building owner under section 10(11)
  3. 3technicalvery strongMinistry of Housing, Communities and Local Government.RN-BUE914Approved Document B Volume 1, fire safety in dwellings, 2019 edition with the 2020, 2022 and 2025 amendments and the forthcoming 2026 and 2029 changes collated in. Covers means of warning and escape, internal fire spread through linings and structure, external fire spread and access for the fire service. This is the document behind escape window sizes, protected stairways, the 4.5 metre rule and the fire doors a loft conversion needs.
  4. 4technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-C6XFB7A party structure notice must be served at least two months before the date on which the proposed work will begin, and must state the building owner's name and address, the nature and particulars of the proposed work (with plans, sections and load particulars where special foundations are proposed) and the date the work will begin. The notice ceases to have effect if the work has not begun within twelve months of service or is not then prosecuted with due diligence. Two months for a party structure notice against one month for a section 6 excavation notice is the distinction to cite.
  5. 5technicalvery strongGOV.UK, a government page.RN-FM4G39The official list of competent person schemes and what each one covers, plus what self-certification means: a registered installer certifies their own work as compliant and notifies building control, instead of the council inspecting it. This is the source for which trades can self-certify what, which is why a FENSA or Gas Safe registered installer does not need a separate building notice.
  6. 6technicalgoodThe Joint Contracts Tribunal, a page from the body itself.RN-D2653HThe publisher's own product page for the JCT Home Owner contract variant intended for a home owner or occupier who has appointed a consultant to administer the contract on their behalf, which is the HO/C form as distinct from HO/B where the homeowner deals with the builder directly. It sits in JCT's Home Owner Contracts category, the suite JCT publishes specifically for domestic building work rather than commercial projects. Use this to confirm which JCT home owner form applies when a note tells a reader to put the job on a written standard contract.

  1. Building Regulation costs, Building Control fees, Belfast City Council Building Control, accessed 16 September 2026. Priced at 2026-04, so no calibration is needed. belfastcity.gov.uk

  2. Fixed-Fee Party Wall Surveyor Cost London 2026 Guide, Survey of Party Wall, accessed 17 September 2026. Priced at 2026-09, so no calibration is needed. surveyofpartywall.co.uk

  3. Approved Document B (fire safety) volume 1: Dwellings, 2019 edition incorporating 2020, 2022 and 2025 amendments collated with 2026 and 2029 amendments, HM Government (GOV.UK), accessed 9 September 2026. assets.publishing.service.gov.uk

  4. Party Wall etc. Act 1996, section 3: party structure notices, legislation.gov.uk, accessed 9 September 2026. legislation.gov.uk

  5. Competent person schemes, GOV.UK, accessed 9 September 2026. gov.uk

  6. Building Contract and Consultancy Agreement for a Home Owner/Occupier (JCT HO/C), The Joint Contracts Tribunal, accessed 9 September 2026. jctltd.co.uk