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Loft Conversion Plans & Dormer Drawings
Complete drawing packages for dormer, Velux, hip-to-gable and mansard attic conversions. Planning drawings, structural calculations and building regulations detail — prepared for UK councils and building control, fully online.
Every Common Loft Conversion, Drawn and Detailed
A loft conversion is the most cost-effective way to add a bedroom and bathroom to a UK home without losing garden space. The right approach depends on your roof type, the head height available and whether the work falls within permitted development.
We draw all the standard conversion types and will advise which suits your roof before you commit. Where a proposal sits close to a permitted development limit, we will tell you plainly rather than drawing something likely to attract an enforcement notice.
Rear Dormer Conversions
The most common route to full head height and usable floor area. Flat-roof or pitched dormers drawn with matched materials and set-in dimensions.
Velux & Rooflight Conversions
The least intrusive option where head height already exists. No change to the roof profile, and almost always permitted development.
Hip-to-Gable Conversions
Squares off a hipped roof to a vertical gable, unlocking substantial extra volume on semi-detached and end-terrace properties.
Mansard Conversions
The steepest-sided option, maximising internal volume. Frequently required in conservation areas and on period terraces.
Roof Lifts
Where existing head height falls short, the ridge is raised. Almost always requires full planning permission.
Loft Conversions in Flats
Top-floor flat conversions, including the additional fire safety and party wall considerations these bring.
Permitted Development or Full Planning Permission?
Many loft conversions fall within permitted development rights, meaning no planning application is required — though you will still need building regulations approval. The volume allowance is 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached properties, measured against the original roof space.
Permitted development rights are removed in conservation areas, on listed buildings, and where an Article 4 direction applies. Front-facing dormers and roof extensions beyond the highest part of the existing roof also fall outside permitted development. We will assess which route your project takes and can prepare a Lawful Development Certificate application where you want the permitted development position formally confirmed.
- check40 cubic metres — volume allowance for terraced houses under permitted development
- check50 cubic metres — volume allowance for detached and semi-detached properties
- check200mm set-in rule — dormers must generally be set back from the original eaves
- checkNo front elevation dormers — roof extensions facing a highway fall outside permitted development
- checkMaterials to match — the external appearance must be similar to the existing house
- checkArticle 4 & conservation areas — permitted development rights may be withdrawn entirely
The Detail Building Control Will Ask For
Every loft conversion needs building regulations approval regardless of whether planning permission is required. The two areas that catch homeowners out most often are fire safety and structural adequacy, and both need to be resolved on the drawings before work starts.
Converting a loft creates a new storey, which changes the escape route requirements for the whole house. In a standard two-storey property becoming three storeys, the staircase enclosure must generally achieve 30 minutes' fire resistance, with fire doors to habitable rooms off the protected route and mains-wired interlinked detection throughout.
- checkPart B — Fire safety — 30-minute protected stair enclosure, fire doors and interlinked mains-wired detection
- checkPart A — Structure — new floor joists, steel beams and the connection to existing structure
- checkPart L — Conservation of fuel — insulation between and over rafters to meet current U-value targets
- checkPart K — Stairs — pitch, headroom and going for the new staircase, including space-saver options
- checkPart F — Ventilation — background ventilation and extract to any new en-suite
- checkHead height — a practical working minimum of around 2.2m before conversion in most cases
Planning, Structural and Building Regulations in One Package
Our Full Package brings planning drawings, structural calculations and building regulations drawings together for £2,700 — which is where most loft conversions land, since nearly all of them need both planning-standard drawings and structural design for the new floor and supporting steelwork.
You receive existing and proposed floor plans, all affected elevations, a cut section through the conversion showing the insulation build-up and fire strategy, and the structural calculations for the new joists and beams, with member sizes annotated onto the drawings for your builder.
Loft Conversion Drawings — From £1,800
Planning drawings alone are £1,800. Most loft conversions need structural design as well, so the Full Package at £2,700 — planning drawings, structural calculations and building regulations drawings combined — is the usual choice and works out cheaper than booking separately.
Loft Conversions — Frequently Asked Questions
Do I need planning permission for a loft conversion?
Many loft conversions fall within permitted development, with a volume allowance of 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached properties. Full planning permission is generally required for front-facing dormers, roof lifts beyond the existing ridge, and any work in a conservation area or where an Article 4 direction applies. Send us your details and we will confirm which route applies.
How much head height do I need for a loft conversion?
As a practical guide, you want around 2.2 metres from the top of the existing ceiling joists to the underside of the ridge before conversion. Once the new floor structure and insulation are installed, this typically leaves a usable finished head height. Where the existing height falls short, a dormer, mansard or roof lift can create it.
What is a hip-to-gable loft conversion?
A hip-to-gable conversion squares off a sloping hipped roof end into a vertical gable wall, which substantially increases the usable volume in the loft. It is a common approach on semi-detached and end-terrace properties, and is frequently combined with a rear dormer.
Do loft conversions need structural calculations?
Almost always. A loft was not designed as a habitable floor, so new floor joists and usually steel beams are required to carry the additional loading. Building control will require calculations demonstrating these are adequate, along with details of how they connect to the existing structure.
What fire safety requirements apply to a loft conversion?
Converting a loft in a two-storey house creates a third storey, which triggers additional Part B requirements. The staircase enclosure generally needs 30 minutes' fire resistance, with fire doors to habitable rooms off the protected escape route and mains-wired interlinked smoke detection throughout the property.
How much do loft conversion plans cost?
Planning drawings alone are £1,800. Because nearly every loft conversion also needs structural design, most clients take the Full Package at £2,700, which combines planning drawings, structural calculations and building regulations drawings and is cheaper than booking each separately.
Can you draw a loft conversion in a flat?
Yes. Top-floor flat conversions are more involved than a house — there are additional fire safety requirements, and leasehold and party wall considerations to work through — but we regularly prepare drawings for them.
Do you visit the property to measure the loft?
No. We send you a measuring kit including a laser measurer with a guide showing exactly which dimensions and photographs we need from the loft space. You take them at your convenience and we draw from there.
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Tell us about your project and we'll come back within 24 hours with a fixed price and a confirmed two-week delivery slot. No site visit required — we work remotely right across the UK.
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