Loft conversion guides
The planning and Building Regulations rules that decide what you can build in your loft — written from the GPDO and the Approved Documents themselves, with every clause cited so you can go and read it.
12 guides · last reviewed
Planning & Permitted Development
Whether you need planning permission, what the GPDO actually allows, and what changes when your street is designated.
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.
Read the guidePermitted Development rules for loft conversions
Class B and Class C of the GPDO 2015, explained clause by clause: volume limits, ridge height, eaves setback, highway frontage, materials and side windows.
Read the guideThe 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.
Read the guideLoft 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 Why Class B is withdrawn and Class C is not.
Read the guideArticle 4 Directions and loft conversions
An Article 4 Direction lets a council withdraw Permitted Development rights across a named area. What it can remove, how to find yours, and how to read it.
Read the guideLawful Development Certificates for loft conversions
Permitted Development is self-assessed, which is a problem when you sell. An LDC is the council's written confirmation that your loft conversion was lawful.
Read the guideConversion types
Rooflight, rear dormer, hip-to-gable — what each one costs you in volume allowance, and what it buys you in usable room.
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.
Read the guideHip-to-gable loft conversions
Squaring off a hipped roof end to a vertical gable. What it costs in Permitted Development volume, which houses can have one, and when to pair it with a rear dormer.
Read the guideRooflight loft conversions
A rooflight conversion adds no volume, sits under Class C, and survives designated land. The 150mm rule, what it costs you in headroom, and when it is the right call.
Read the guideBuilding Regulations
The rules that still apply even when you need no planning permission at all: fire, stairs, headroom and insulation.
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.
Read the guideLoft 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.
Read the guideLoft conversion staircase rules
Pitch, rise, going, width, headroom and landings for a loft stair — including the headroom relaxation that exists specifically for loft conversions.
Read the guideSkip the reading — check your own roof
The guides tell you what the rules are. The assessment tells you what they mean for your property: enter your postcode and roof dimensions and we work through every Permitted Development condition against your actual numbers.
Start the free assessmentFree to check. The £29 full report is fully credited against your full structural design.