Your Guide on Permitted Developments for Loft Dormer – No Planning Required?
What is a dormer extension?
A dormer is a roof extension that creates additional headroom (of course) and usable space in your loft. It typically involves building a vertical wall from the roof slope and adding a flat or pitched roof on top. This can also be known as “loft conversion”. In other words, imagine a rectangle sticking out at the back of your roof. Not sure if this helps, but hey! Of course, it’s not just a box. The beauty shines at the end when everything else is added.
And most often, dormers are commonly built at the rear of a property and are often used to create a new bedroom, office or bathroom in the loft.
So, what is Permitted Development (PD)?
Permitted Development is a national set of planning rules that allow homeowners to make certain types of extensions and alterations without needing full planning permission.
We know you have been told, every and anything that is built or extended needs planning permission from the council. But luckily your reading this article, and now you know that is not true. You have saved time and money. But wait! Have you really?
Well, a dormer can fall under PD ONLY if it meets specific size, height, and position rules. We will advise you clearly if your proposed dormer qualifies.
Now, what does the process involve?
1. Measured Survey
Firstly, an architectural designer will visit your home to accurately record the layout, structure, and roof dimensions.
2. Concept Design
Then they will design a dormer that maximises space while complying with PD limits. We’ll also advise on internal layout, stair access, and headroom.
3. Lawful Development Certificate (optional but recommended)
While this is not legally required, we strongly recommend applying for a Lawful Development Certificate to prove your dormer was built lawfully under PD rules. This protects your future resale or remortgage.
4. Building Regulations Drawings
Last but not least, dormers must comply with building regulations, especially structure, insulation, fire escape, and drainage. We prepare a detailed set of drawings for Building Control and your builder.
What are the benefits of a dormer under PD?
- No formal planning application needed
- Faster start on site
- Extra space and added value without changing the footprint
What are the risks or things to watch out for?
- Your dormer must not exceed 40 m³ (around 3.4 m x 3.4 m x 3.4 m terraced) or 50 m³ (around 3.68 m x 3.68 m x 3.68 m semi-detached/detached) including any previous roof extensions.
- It is lower than the highest part of the existing roof – usually the ridge.
- It must be set back at least 200 mm from the eaves.
- You can’t add balconies or raised platforms or alter the front roof slope under PD.
- Article 4 direction areas remove PD rights; you’ll need to check with your council.
- Loft conversions are NOT permitted development for houses on designated land.
We’ll confirm all of this before you commit.
Do I need a builder or a project manager?
We provide the design, compliance and technical documentation. You’re free to appoint your builder, or we can refer trusted contractors. For more involved projects, we can act as the principal designer to help manage compliance and reduce risk.
How long will it take?
Typical timeline:
- Survey to final design: 2–3 weeks
- Lawful Development Certificate (if applied): 8 weeks
- Building Regulations approval: 1–2 weeks
- On-site works: Usually 4–6 weeks, depending on builder and scope
Summary
Building a dormer under permitted development is one of the quickest and most cost-effective ways to unlock your loft’s potential.
At Studio Tashkeel, we make sure it’s designed smartly, drawn accurately, and built legally—so you can extend with confidence.
From roof to room—done right.
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