Will your loft conversion qualify as Permitted Development?
Check your loft against every Permitted Development condition in minutes, free. Then get the full volume working, drawings and compliance position — the evidence for your Lawful Development Certificate — before you commit to an architect or a build.
Free to check — and the £29 report is credited in full if you go ahead with your structural design
How it works
Enter your details
Tell us about your property — postcode, roof type, and basic dimensions.
Get instant results
We check Permitted Development rules, calculate volumes, and assess feasibility in real time.
Download your report
Get the full PDF: volume working, drawings and your position on every condition — the evidence for your Lawful Development Certificate. £29, credited in full when you instruct your structural design.
What the £29 gets you
The free check tells you the verdict. The report gives you the evidence — fully credited against your full structural design
What it's for
- The evidence base for a Lawful Development Certificate — the application that proves your conversion is lawful before you build
- A brief for your architect and engineer, so you are not paying them to re-derive it
- A permanent record of your property's Permitted Development allowance — it is cumulative, so it matters at the next project and at resale
What it isn't
The submission drawings themselves, or any structural, fire, staircase or insulation design. Those are your architect's and engineer's work — and your £29 comes off our structural package.
Tell us about your property
We'll check whether your loft conversion qualifies under Permitted Development
What type of house is it?
This sets how much roof volume you may add without planning permission. An end-of-terrace counts as terraced.
How many storeys?
Count floors above ground level, not including the loft. This assessment covers 1–2 storey houses.
Does it have a basement?
A basement counts as an extra storey for fire safety, even though it sits below ground — see the note above on what a third storey changes.
Your postcode
Some areas have had Permitted Development rights restricted or withdrawn. We check yours against the government's national planning dataset — Conservation Areas, National Landscapes and Article 4 Directions.
You can skip this — but we'll then assume no restrictions apply, which is the optimistic answer. If you know your street is in a Conservation Area, set it manually rather than skipping.
Any previous roof extensions?
Earlier loft conversions, dormers and hip-to-gables come out of the same volume allowance as your new work — even if a previous owner built them. Rooflights and re-tiling don't count.
Select your property type and number of storeys to continue
Frequently asked questions
Permitted Development (PD) rights allow you to extend or alter your home without a full planning application, subject to specific rules set out in the General Permitted Development Order (GPDO). Most loft conversions — including rear dormers — can be done under PD if they comply with volume, height, and setback limits.
Most loft conversions in England don't need planning permission if they stay within Permitted Development limits. However, if your property is in a Conservation Area, AONB, or subject to an Article 4 Direction, additional restrictions may apply — especially for dormers visible from the street.
The £29 you pay for your report is credited in full against your structural design package if you instruct us to carry out the full structural design. In other words, the report acts as a deposit — go ahead with your loft conversion and it effectively costs you nothing.
Our assessment uses the measurements you provide and the rules from the GPDO to give you an indicative feasibility check. For a definitive answer, you should apply for a Lawful Development Certificate (LDC) from your local council. Our report gives you everything you need to start that process.
A rooflight conversion adds windows to the existing roof slope without changing the shape. It's cheaper but gives less headroom. A rear dormer extends the roof outward at the back of the house, creating a flat-ceilinged room with significantly more usable floor area.
For terraced houses, the limit is 40m³ of additional roof volume. For semi-detached and detached houses, it's 50m³. This includes the volume of any dormer and any previous roof extensions or alterations to the original roof.
Yes. Even if your loft conversion doesn't need planning permission, it must comply with Building Regulations. This covers structural safety, fire safety, insulation, staircase design, and more. Our report includes guidance on the key regulations you'll need to meet.
An LDC is a certificate from your local planning authority confirming that your proposed works are lawful under Permitted Development. While not legally required, it's strongly recommended — it protects you when selling and provides proof that no planning breach has occurred.
Know the rules before you start
Written from the GPDO and the Approved Documents themselves, with every clause cited so you can go and read it.
Do I need planning permission for a loft conversion?
Most loft conversions in England need no planning permission — they are Permitted Development. Here are the six conditions that decide it, and the cases that fail.
The 40m³ / 50m³ volume allowance, explained
How much roof volume Permitted Development lets you add, what 'original' means, why the allowance is cumulative, and how a rear dormer's volume is actually calculated.
Rear dormer loft conversion rules
The Permitted Development limits that shape a rear dormer: volume, ridge height, the 200mm eaves setback, highway frontage, matching materials and side windows.
Loft conversions in a Conservation Area
A dormer is not Permitted Development in a Conservation Area — but a rooflight conversion usually still is. Why Class B is withdrawn and Class C is not.
Loft conversion head height
There is no legal minimum ceiling height for a loft room. 2.2m is a practical guideline, not a regulation — and the number that matters is the finished height after build-up.
Building Regulations for loft conversions
Every loft conversion needs Building Regulations approval, whatever the planning position. Fire safety, stairs, structure and insulation — what each Approved Document requires.
Work with LoftNow
For architects and designers
Structural output only
LoftNow reports cover feasibility and indicative structure. We never produce Building Regs drawings — that work stays with architects and designers.
Drawing work referred out
LoftNow customers who need Building Regs drawings get referred to partner practices near them.
Free to join
Join as a partner practice — free, no commitment — and you're in the flow for the next loft job near you.
We reply personally to every sign-up within 2 working days.