Two loft conversion quotes for the same house can sit thousands of pounds apart, and the cheaper one is rarely the better deal. Often the gap is not about value at all. It is about what one builder has left out. A good quote names every major item in plain words. Use this loft conversion quote checklist to compare like for like before you pay a deposit.
The checklist: 8 groups to check
- Design. The conversion type (Velux, dormer, hip-to-gable or mansard), floor area, headroom and number of rooms. Quotes for different types cannot be compared.
- Structure. Steel beams, structural engineer calculations and floor strengthening. Check whether steel is priced or only “allowed for”, and who pays the engineer.
- Approvals. Planning permission or a lawful development certificate if needed, building regulations fees and sign-off, and any party wall costs.
- Access. The new staircase, fire doors and protected escape route. Stairs are one of the most commonly missing items.
- Weatherproofing. Insulation, roof windows and dormer cladding, with the specification stated.
- Services. Electrics, heating extension and plumbing for any en-suite.
- Finishes. Plastering, flooring, doors and decoration. “Ready to paint” and “fully decorated” are very different prices.
- Site costs. Scaffolding, skip hire and dust protection.
Ask every builder to answer the same eight groups in writing. Where an item is missing, request a priced line, not a verbal promise. This one step makes quotes comparable and exposes gaps early.
Do the approvals need checking separately?
Yes. Many loft conversions in England are permitted development, but not all, so confirm your case using the Planning Portal and the technical guidance. Building regulations are a separate requirement. If beams bear into a shared wall, the Party Wall etc. Act 1996 (England and Wales) may apply. Scotland and Northern Ireland have their own rules.
What is not included in a loft conversion price?
Watch for wording that quietly moves cost back to you:
- “By others”: someone else pays, often you. Common for steel, stairs and electrics.
- Provisional sums: a placeholder amount that can rise once work starts.
- “Subject to survey”: the price may change after the roof is opened up.
Hidden costs: extras that appear after you sign
Extras usually surface once the roof is opened: damaged timbers, wiring upgrades or extra fire safety work. Ask how each will be priced, whether by fixed price or day rate, and who approves it before work goes ahead.
Commercial terms to compare
Check the VAT basis, payment schedule, timeline, warranty, insurance and how variations are priced and approved in writing. Before paying a deposit, ask what each stage payment is tied to, such as completed milestones rather than calendar dates. These terms can matter as much as the headline number. For a wider look, see our guide to comparing builders’ quotes.
Worked example: why the cheapest quote can cost the most
Here are three hypothetical quotes for the same dormer conversion. We have added the items each one left out.
| Quote | Headline | Missing items added back | Adjusted total |
|---|---|---|---|
| Builder A | £51,000 | None, fully itemised | £51,000 |
| Builder B | £47,000 | Scaffolding and skip (£3,200) | £50,200 |
| Builder C | £41,000 | Stairs (£5,000), steel and engineer (£5,500) | £51,500 |
Illustrative figures only, not real quotations.
Builder C looked £10,000 cheaper and ended up the most expensive. Always ask for missing items to be priced in writing before you compare totals. Real prices vary widely by region, type and specification, and published guide prices differ between sources, so treat any average as a starting point only.
Red flags in a loft conversion quote
| Red flag | Why it matters |
|---|---|
| One lump sum, no breakdown | You cannot see what is covered or compare it. |
| Steel or stairs “by others” | Large costs may appear later. |
| Big provisional sums | The final price may be much higher. |
| No building regulations sign-off | It could cause problems when you sell. |
| No insurance or warranty details | You may have little protection if something fails. |
How ScopeCheck helps
Reading several quotes line by line is slow. ScopeCheck lines up each quote so you can see what is included, what is excluded and where the gaps are. See an example report, or compare loft conversion quotes now. ScopeCheck is a decision aid, not a guarantee.
Frequently asked questions
Does a loft conversion quote include building regulations?
Not always. Check whether building control fees and inspections are listed, and who handles the final sign-off.
Does a loft conversion quote include stairs?
Not always. Ask for the staircase design, finish and the work around the opening to be written in.
Does a loft conversion quote include VAT?
It varies. Ask every builder to state clearly whether prices include VAT, so totals match.
Is a structural engineer included?
Sometimes it is a separate fee. Confirm who commissions and pays for the calculations.