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How much does a dormer loft conversion cost?
In Cheshire, a dormer loft still needs its own quote, while the Federation of Master Builders guide of 5 June 2026 says a dormer averages around £50,000, and its loft guide of 3 September 2025 lists a dormer at £50,000 [S8][S9]. Prices vary by the job and the location, and QuoteZila does not set prices.
Last reviewed:A box on the slope, not a product
A dormer loft conversion in Cheshire means cutting a new structure out of the roof so the space can be stood in. Terraces and semis around Crewe, Nantwich and Sandbach are the houses this guide starts from, and each one still has its own stair, floor and slope. The Federation of Master Builders' renovation guide of 5 June 2026 says a dormer averages around £50,000, and its loft conversion cost guide of 3 September 2025 lists a dormer at £50,000 and says the prices come from member firm Marken Lofts [S8][S9]. That is not a Cheshire price. Prices vary by the job and the location, and QuoteZila does not set prices. Ask for the volume, the stair position and the slope to be written down before you compare one builder with another.
The Planning Portal treats the enlargement of a house roof as permitted development only inside a list of limits [S3]. The limits are measurements. They are not a builder's rate. A dormer that stays inside them can still be expensive, and a dormer outside them can still be buildable if permission is granted. Do not ask a contractor for "a permitted development price" as if that were a specification.
Volume, the front slope, and windows
For a house, the volume of enlargement, including any earlier enlargement, must not exceed 40 cubic metres if the house is terraced, or 50 cubic metres otherwise [S3]. The new work must not stick up above the existing roof [S3]. On the principal elevation, where it fronts a highway, it must not project beyond the existing roof slope [S3]. That is why many people ask for a dormer on the rear. If your "rear" is actually a side that faces a road, the principal-elevation test may be the one that matters. The council, not this page, decides the elevation.
The same page excludes verandas, balconies and raised platforms, and it excludes installing, altering or replacing a chimney, a flue, or a soil and vent pipe [S3]. Side-facing windows must be obscure-glazed and, if they open, the opening parts must be 1.7 metres above the floor of the room [S3]. The original eaves have to be maintained or put back. Any enlargement is set back, so far as practicable, at least 20cm from the original eaves. The enlargement must not overhang the outer face of the original wall [S3]. The Portal lists exceptions to parts of that construction test, including for relevant parts of a hip-to-gable enlargement. Read the exceptions on the Portal page rather than treating this paragraph as the whole rule.
The house itself must not be a flat, or a building that contains a flat [S3]. Article 2(3) designated land, which includes conservation areas and areas of outstanding natural beauty among other designations, is outside these limits [S3]. A dormer in a conservation area in Cheshire is a planning application until someone at the council says otherwise.
A liveable room is building regulations work
Planning permission and building regulations approval are different. The Planning Portal says approval under the building regulations is required to turn a loft or attic into a liveable space [S4]. The guidance it gives is aimed at an existing house of no more than two storeys [S4]. It describes a liveable space as a room for normal use as part of the home [S4]. A spare bedroom you rarely use is still that kind of room if it is a bedroom. Flats, maisonettes and houses over three storeys sit outside that two-storey guidance. The Portal says the requirements there will be similar but may be more extensive, and may extend to other parts of the building [S4]. Ask building control rather than stretching the two-storey note.
GOV.UK: find your local council for building control. QuoteZila is not affiliated with this organisation.
The quote should say who applies, or who self-certifies, and what the stair and the floor are made of. This page does not state a joist size. It says the Portal expects the conversion to deal with the strength of the floor and the way you get out if there is a fire, among other things, by requiring approval at all [S4]. Leave the engineering in the written specification.
The party wall on a terrace
GOV.UK says the Party Wall etc. Act 1996 stands apart from planning permission and from building regulations approval [S5]. A building owner who proposes work the Act covers must give adjoining owners a party wall notice in the way the Act sets down [S5]. The examples include cutting into a party wall [S5]. A dormer that bears on a wall shared with next door can be that kind of work. It is not automatic for every semi. Ask each builder, in writing, whether they think the Act applies and whether their fee for dealing with it is included. Where it applies, serve a party wall notice before the roof is opened.
Excavation near a neighbour's foundations is also in the Act [S5]. A loft does not always need a new foundation. If the quote includes steel that lands on a wall, ask where the load goes. Do not assume a roof job stays in the roof.
No method for opening the roof
HSE says roof work must be organised so it is done safely, and that all work on roofs is highly dangerous even when the task is short [S6]. The people on the roof must be trained and competent [S6]. Work at height, in HSE's wider definition, includes a place where someone could fall far enough to be injured, for example through a fragile roof, and it should be avoided where that is reasonably practicable [S7]. You do not cut a dormer opening as a householder project from this page. You do not go out of a roof window to photograph the lead. Photos of the landing, the loft hatch and the rear slope from the garden are the pack to send.
HSE: work at height. QuoteZila is not affiliated with this organisation.
What the quotes are actually pricing
Citizens Advice wants a written quote, not a verbal guess, and treats a refusal to write it down as a warning [S1]. Some firms charge to quote, so ask before the survey [S1]. The written price should be a fixed total, say whether VAT is in it, and say how long it lasts [S1]. VAT registration is required when taxable turnover for the last 12 months goes over £90,000, or is expected to in the next 30 days [S2]. If you cannot avoid a deposit, do not agree more than 25%, and keep a receipt [S1].
| Piece of the dormer | What "included" must mean |
|---|---|
| Volume | Cubic metres they have designed, against the 40 or 50 cap [S3] |
| Which slope | Rear, side, or a face that fronts a highway [S3] |
| Stair | Where it lands, and that it is in the total |
| Floor and structure | Named, not "as required" with no drawing |
| Windows | Side windows obscure, opening parts at 1.7 metres where that rule applies [S3] |
| Set-back | At least 20cm from the original eaves so far as practicable [S3] |
| Party wall | Whether a party wall notice is expected [S5] |
| VAT | Stated, beside the £90,000 threshold [S2] |
What to hand over
- House type: terrace, semi, detached, or a flat (a flat is outside the house limits [S3]).
- A sketch of where the stair could go, even if it is rough.
- Loft photos from the hatch, not from the roof slope.
- Whether a dormer or a rooflight was added before. Earlier enlargement counts toward the volume [S3].
- Conservation area, if you know.
- Postcode.
Anyone in the UK can post a job or register. QuoteZila is new, so the number of loft builders who reply depends on who has joined near you [QZ5].
Jobs you might post
These are examples, not taken from real job posts.
- Rear dormer on a two-storey semi, stair from the landing, no balcony. Ask the firm to state the volume and whether a party wall notice is needed.
- Dormer plus a new loft floor strong enough for a bedroom, with building regulations approval named in the quote.
- Survey only, in writing, of whether a dormer on this roof can stay inside the Portal limits, with no building work priced yet.
Reading dormer quotes
Match the stair, the volume and the finishes before you match the totals. A shell price with the bathroom "by others" is not the same job as a finished bedroom. Citizens Advice says a much lower price can mean the work is not like for like [S1]. Pay in stages by card if you can, rather than the whole sum before the roof is opened [S1]. Check insurance yourself [S1].
Official pages
QuoteZila is not affiliated with these organisations.
- Citizens Advice [S1].
- GOV.UK VAT [S2].
- Planning Portal loft planning [S3].
- Planning Portal loft building regulations [S4].
- GOV.UK party walls [S5].
- HSE roof work [S6].
- HSE work at height [S7].
This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.
Post a dormer
Describe the house and the town. Up to five matched local businesses can reply [QZ2]. QuoteZila is free for customers and local businesses [QZ1].
Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.
Posting a job is not open yet
Builders and roofers cover the trades. Scaffolders are a separate page if access is its own hire. Electrical work in the new room has its own Cheshire guide: electrician cost. A repair that is not a conversion sits in roof repair cost. All services.
Questions about dormer lofts
How much does a dormer loft conversion cost in Cheshire?
The Federation of Master Builders' renovation guide of 5 June 2026 says a dormer loft conversion averages around £50,000, and its loft guide of 3 September 2025 lists a dormer at £50,000. The September guide says those prices come from member firm Marken Lofts and depend on location, complexity and materials. The figure is not a Cheshire price. Stair position, floor strength and the size of the dormer still change the job. Prices vary by the job and the location, and QuoteZila does not set prices.
What volume can a dormer add?
The Planning Portal says enlargement of a house roof, including earlier enlargement, must not exceed 40 cubic metres for a terraced house or 50 cubic metres otherwise. It must not exceed the height of the existing roof. The house must not be a flat or a building containing a flat.
Can the dormer face the street?
On the principal elevation, where that elevation fronts a highway, the enlargement must not extend beyond the existing roof slope. A rear dormer is a different face. Article 2(3) designated land is outside these permitted development limits. Ask the council if you are unsure which elevation you have.
Do I need building regulations approval?
Yes for a liveable loft. The Planning Portal says building regulations approval is required to convert a loft or attic into a liveable space, and its guidance is aimed at an existing house of no more than two storeys. A room used as a normal part of the home counts.
What about the neighbour in a terrace?
GOV.UK says the Party Wall etc. Act 1996 is separate from planning permission and building regulations approval, and that the building owner must give a party wall notice in the way the Act sets down. Cutting into a party wall is among the examples. A dormer on a terrace can be that situation. This page cannot tell you that it is.
Does QuoteZila check loft firms?
No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.
Can I post a dormer on QuoteZila?
Yes. Say rear or side, name the house type, and add a Cheshire postcode. Up to five matched local businesses can quote. QuoteZila is free for customers and local businesses.
Related reading
Part of Cost guides. All services
Related trades
Cost guides
Related pages
- Extension with a loft: what changes the price. In Cheshire, pricing an extension and a loft together means two rule-sets and one structure. No pound total is printed. See how to split the quote.
- Flat Pack Houses: Separate the Quote Lines. A flat pack house in Cheshire is still a new building. Separate the kit from planning, building regulations, the foundations and the services on the plot.
Sources
- QZ1: QuoteZila product fact. QuoteZila pricing line.
- QZ2: QuoteZila product fact. QuoteZila FAQ How does getting quotes work?.
- QZ5: QuoteZila product fact. QuoteZila home honest-status callout.
- S1: Before you get work done on your home, Citizens Advice. Accessed 2026-10-25. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
- S2: When to register for VAT, GOV.UK. Accessed 2026-10-25. https://www.gov.uk/register-for-vat
- S3: Planning permission: loft conversion, Planning Portal. Accessed 2026-10-25. https://www.planningportal.co.uk/permission/common-projects/loft-conversion/planning-permission/
- S4: Is building regulations approval needed for a loft conversion?, Planning Portal. Accessed 2026-10-25. https://www.planningportal.co.uk/permission/common-projects/loft-conversion/is-building-regulations-approval-needed-for-a-loft-conversion
- S5: Party Wall etc. Act 1996 guidance, GOV.UK. Accessed 2026-10-25. https://www.gov.uk/guidance/party-wall-etc-act-1996-guidance
- S6: Roof work, Health and Safety Executive. Accessed 2026-10-25. https://www.hse.gov.uk/construction/safetytopics/roofwork.htm
- S7: Introduction to working at height safely, Health and Safety Executive. Accessed 2026-10-25. https://www.hse.gov.uk/work-at-height/introduction.htm
- S8: How much does a house renovation cost?, Federation of Master Builders. Accessed 2026-10-30. https://www.fmb.org.uk/resource/how-much-does-a-house-renovation-cost.html
- S9: Loft conversion cost: a breakdown of costs, Federation of Master Builders. Accessed 2026-10-30. https://www.fmb.org.uk/resource/loft-conversion-cost-a-breakdown-of-costs.html