Our guide to planning permission for loft conversions

Lofts represent both potential and opportunity. They’re often overlooked and underused, but with a little design inspiration, they can be turned into unique, eye-catching and functional spaces. Whether you need an additional bathroom or bedroom, or perhaps a quiet place to work, there are endless ways in which a loft conversion can transform your home. 

Before we get carried away with design plans, it’s worth looking into the rules and regulations. In this post we’ll explain whether you need planning permission for a loft conversion, and how to go about obtaining it if you do.

Do I need planning permission for a loft conversion?

In most cases, planning permission isn’t required for loft conversions. This is because they tend to be considered a ‘Permitted Development’. This is a type of property extension which conforms to various criteria. These include:

  • The total additional space of an extension cannot exceed 40 cubic metres for a terraced property, or 50 cubic metres for a semi-detached or detached property (*note – previous additions to your property, even those made before your ownership, contribute to this limit).
  • The extension cannot extend the height or forward-most point of your current property.
  • Side-facing windows need to be obscured and stand at least 1.7m above the floor.
  • Except for hip to gable loft conversions, the conversion will need to be set back as far as practicable with a minimum of at least 20cm from the original eaves.
  • There are no raised platforms, verandas, or balconies.
  • The roof extension can’t overhang the outer face of the wall of the original property.
  • The property can’t be on designated land such as a national park, conservation area or a world heritage site.

Do I need planning permission for a dormer loft conversion?

As one of the most popular types of loft conversion, a dormer loft involves building an upright structure from a sloping roof. This results in more usable floorspace within a loft and gives occupants more headroom. When it comes to planning permission, dormer conversions are treated the same as other types of loft conversion; as long as it can be classed as a ‘Permitted Development’, you won’t need planning permission. 

How long does it take for planning permission for a loft conversion?

If you need to apply for planning permission for your loft conversion, the process can take up to 8 weeks to complete. Bear in mind, though, that it can be longer for more complex projects that require significant structural changes. 

Do I need buildings regulations approval for a loft conversion?

Yes. Building regulations approval is separate from planning permission, and is required regardless of whether your extension is a ‘Permitted Development’. This type of approval ensures that your intended extension is structurally viable, is compliant with fire safety rules, and has adequate sound insulation. Inspections are made before, during, and after construction by a building control service to make sure that every aspect is in line with regulations. 

interior photography

Loft conversions with Plus Rooms

We hope this short guide to planning permission for loft conversions proves helpful in your project. If there is anything you are still unsure about, feel free to get in touch. With extensive experience creating beautiful loft conversions in and around London, we’d be happy to help. And if you’d like some inspiration, take a look at some of our past loft conversion projects

Build It Jan 2021

Can I extend without planning permission?

Anamika Talwaria looks at the ways you can add extra space to your home without putting time and money into gaining consent

Building an extension is a great way to add space and value to your home while avoiding the rigmarole of moving to a new house entirely. But the planning process can sometimes be lengthy and costly, plus there’s no guarantee that you’ll definitely secure consent to build the design you want. Thankfully, there’s a route to achieving modest but transformative extensions without undergoing the uncertainly of going in for planning permission.

Plus Rooms created the rear extension to this terraced property incorporating a monopitched roof and rooflights. Huge glazed doors offer stunning views onto the garden from the new open-plan kitchen-dining space.

Do I need a designer?
While hiring someone to draw up your plans of your home is generally a sensible idea, some more simple projects can be developed by the main contractor overseeing the build or by another designer. A straightforward rear extension of loft conversion probably doesn’t need an architect, then, but if you’re planning a wow-factor project with specialist materials or complex design features, then it’s almost certainly worth getting a professional in.

Making sure your builders and trades get property drawings can also mean you’ll end up with more accurate quotes for an unusual design, limiting any unexpected costs as the build goes on. That said, if your contractor is drawing up the plans, you may well get a fixed price for the whole job anyway.

Rear extensions
Extending out from the back of your home is often the easiest way to add space, without too much impact on your neighbours. It’s a speedy and cost-effective way to get more useable area in your home, especially where you don’t have wiggle room to expand to the side.

In England and Wales, basic PD rights mean you can build a single storey rear extension reaching up to 4m out from the back wall of a detached house, or 3m for a semi or terrace. The addition must be no higher than 4m. If you want to create a bit more space, in England you can apply for Prior Approval to expand your home up to 8m (if it’s detached) or 6m (semi or terrace). Akin to a slimmed-down planning process, there’s far fewer criteria than a full application, although it does still carry a small fee (296).

Want to add space upstairs, too? Multi-storey rear extensions are possible under PD as long as the addition its neither more than 3m out from the back of the house, nor within 7m of the end of the garden. To keep within the regulations, you will need to make sure that any windows created on the side elevation are obscurely glazed and non-opening. The roof pitch should match the existing house as much as possible.

Side extensions
If you’re lucky enough to have excess space to the side of your property, it can make sense to extend along that elevation. This is typically easiest if you have a detached home set in a large plot, but it can be suited to end-of-terraced and semi-detached properties too. What’s more, many Victorian terraces were designed with a small courtyard area at the rear, which can be infilled to form side-return extension. This kind of project can help to make the most of a compact area.

You’ll need to keep within the size restrictions, and in England that means sticking to a single storey that’s no more than 4m in height (shorter if it’s within 2m of a land boundary). To qualify as PD, the width of the addition must be no more than half that of the of the original house. Side extensions often entail Party Wall Agreements, as the work is likely to be within 6m of neighbouring property.

Loft conversions & extensions
Did you know that building up into the attic can add more value than undertaking a classic kitchen extension? Often a cost-effective option, a loft conversion can provide a whole usable storey of space. You could specify a master suite, home office or even a playroom, and it would be quietly tucked away on the top floor.

Before you start dreaming up possibilities, check the head height throughout the main bulk of the space is at least 2.2m, and that the roof pitch is suitable to allow a good amount of usable floorspace. This will allow for minimum structural intervention, increasing your chances of the project being classed as permitted development. Under PD rights in the UK, you can install rooflights and rear dormer windows without too much fuss, as long as your conversion stays within the realms of the outer walls of the house.

This is one of the quickest and easiest ways to create a suitable living space in the attic. Any windows you stick on the side elevation need to be obscure glazed and non-opening (unless the parts which open are more than 1.7m above internal floor level). The overall conversion must not add more than 50sqm to a semi or detached house, and no more than 40sqm to a terrace. This limit includes any habitable roof space that might have been added by a previous owner.


Just because you’re avoiding a formal planning permission, doesn’t mean you can build whatever you like. There are a range of parameters you need to know about when it comes to permitted development rights. The next few paragraphs relate to England, but the guidance is similar across the UK.

One of the first things to bear in mind is that permitted development rules only apply to houses. So if you live in a flat, maisonette or other style of dwelling, you cannot take advantage of the relaxed regime. PD rights will also be restricted if you live in a designated area, like a national park or conservation area So, look closely at how the rules apply to your location and project And whether you need formal consent or not, your project will always be subject to the Building Regulations.

The size restrictions for different classes of PD extensions and outbuildings relate to the original house. This is defined as the structure as it was when it was first built or as it stood on 1st July 1948 (if it was constructed prior to that date). For instance, additions can’t be bigger than 50% of the land surrounding the original house, and there are size limits for each type of extension, If your property’s PD rights have already been used up, you’ll need to seek full planning consent (unless you intend to knock down and replace an existing extension).

PD rights don’t allow for verandas, balconies, raised platforms or alterations to the roof (with the exception of rooflights and some dormers). They also exclusively forbid building forward of your home’s principal elevation (unless you’re adding a porch), including side elevations that front a main highway. As much as possible, external finishes such as cladding, roof tiles and render should be in keeping with the existing materials. Visit www. for the full list of rules.


It’s not just extensions that can be enabled through permitted development. Here are some of the other works you can do without planning permission that will refresh your home and add value:

Internal remodel Switch up your interiors with a fresh lick of paint, updated flooring, brand new kitchen, creating an ensuite or even moving your walls around. Just be sure to take advice from a structural engineer for load bearing walls.

Add a porch Increase your home’s kerb appeal with a covered area over your entryway. This should be less than 3m2 in footprint and must be more than 2m from the front boundary.

Replace windows & doors Updating the fenestration with new materials, or a change of colour, can breathe fresh life into your property. Opt for double or even triple glazing where appropriate for a higher level of energy efficiency in your home.

Change the external materials Refresh the outside of your home with a lick of paint, or replace tired cladding or render with something similar to the original covering (potentially with a modern twist).

Replace roof tiles We’ve already seen that you can make minor alterations like adding a rooflight or skylight, so consider also changing the covering up top to give your property a whole new look. You could also add solar panels or solar roof tiles for a greener abode.

Garage conversion Normally used for storage, you could turn your garage into a bedroom suite, home office, games room or workshop. As long as the alterations don’t have an impact on the exteriors, this will usually fall under PD (although it can be worth checking with your local authority). By contrast, newly constructed PD outbuildings can’t be used as primary residential accommodation.

Now that so many of us are working from home, building a standalone studio in the back garden might be more appealing than trying to carve out space inside for a home office. Garages, sheds and workshops also fall within this PD category as popular projects that don’t need consent.

To count as PD, outbuildings can only be erected behind the front elevation of your main house. They must be a single storey with a maximum height of 4m with a dual-pitched roof, or up to 3m for any other roof type. If it’s within 2m of a boundary line in the garden, then you can’t build higher than 2.5m. You also can’t include a veranda, balcony or raised platform in the design features like this will need full planning consent.

The rules specify that you can’t take up more than 50% of the land surrounding the original house with build structures. This includes any other extensions you might already have, so you’ll need to take these into account when drawing up your plans. If you’re in a national park, area of outstanding natural beauty, world heritage site or the broads, this is limited even further: you can fill just 10sqm of the land with additional structures. Houses in designated areas, or listed properties, will need formal planning permission and possibly conservation area or listed building consent to construct an outbuilding.

Good Homes Dec 2020


Tessa Milton was inspired by the look and colour palette of her childhood kitchen when designing this relaxing family space


Q? Why did you want to change your existing kitchen?
It was dark and narrow and had a cramped extension stuck on the end, which was only big enough for a tiny dining table. I always knew I wanted to knock it down and build a new extension, so when I had the budget I approached design and build company, Plus Rooms. They took my ideas and provided all the technical know-how, such as how many rooflights would be needed. I knew that I wouldn?t be able to project-manage it myself as I was working full time, so it was reassuring to know that one company could look after everything for me.

Q? Did you face any challenges in the process?
Fortunately, setting up a temporary kitchen in the living room meant we didn?t have to move out, even when the back wall was taken down! The work only took around six months, but it was completed over the winter, which meant we were quite cold at times, especially when the water and heating had to be turned off for a couple of days! As there?s no side or rear access, the builders had to bring everything through the house, but they were extremely careful and considerate. My tip would be to order items such as taps early, because any delivery delays can hold up the project.

Q? What inspired your design for the kitchen cabinets?
I worked with my mum to come up with the sage-green colour; she was also an interior designer, and we had a green kitchen when I was growing up. The cabinets were made by a local carpenter from spray-painted MDF, and it took about five attempts before I found the perfect shade! The idea for rattan inserts came from the designer Matilda Goad, who uses it in her designs. I soaked the rattan in water so that it swelled, then cut it to size and attached the panels to the cabinet doors with staples and glue. I?m so pleased with the finished result ? everything in the extension has turned out even better than I could have imagined.



Interior designer Tessa Milton (, lives with children Tom, 14 and Flora, 12, in this three-storey, three-bedroom terraced house in Putney, south-west London

To demolish an existing dated lean-to, extending out to the side of the property to create a wraparound timber-framed kitchen-diner that opens out onto the garden

Design, build & materials ?51,800 Doors & windows ?12,046 Kitchen cabinets ?12,000 Worktop ?5,000 Parquet floor ?3,400 Patio tiling ?1,400 Furniture, lighting & appliances ?24,350

TOTAL SPEND ?109,996

Tessa?s trips to Morocco motivated her to lay encaustic tiles as a patio, bringing colour and interest to the small rear garden and creating a low-maintenance feature to enjoy inside and out

Designing the new layout and cabinetry herself, Tessa chose bespoke sage-green doors inspired by her childhood kitchen, and a glazed Zellige tile splashback. Engineered parquet flooring has been laid over underfloor heating

‘I worked with my mum to come up with colour as we had a green kitchen when I was growing up – it took a few attempts before I found the perfect sage shade’

CREATE HIDDEN STORAGE A practical L-shaped dining bench was made by a local carpenter to Tessa’s specification, which she uses to store items such as cutlery and placements within handy reach of the dining table

Windows & doors, ?12,046, Integral. Habitation Mountain Chalet parquet flooring, ?89.99 per sqm, Claybrook. Antique handmade reclaimed Hacienda patio tiles, ?150 per sqm, Maitland and Poate. Kitchen cabinets, ?12,000, Slawek Smiech. Composite worktop, ?5,000, Stoneworks. Oslo dining table, ?1,749, and bench, ?949, Heal?s. Chair, ?139, Cult Furniture. Aquila wall lights, ?105 each, Pooky. Zellige tiles, ?98 per sqm, Mosaic Factory. Flora mirror, ?940, Balineum. Lucia L bracket wall light, from ?288 each, Hector
Finch. Rattan wave pendant lights, ?160 each, Matilda Goad. LG GSJ560PZXV American fridge-freezer in stainless steel, ?1,249, Appliance City. Rangemaster PDL90DFFSS/C dual-fuel range cooker, ?12,069, Donaghy Bros. Aged brass kitchen tap, ?607, Perrin & Rowe

DESIGN-IN-THE-DETAIL Inspired by designer Matilda Goad, Tessa fitted the distinctive rattan inserts on the cabinetry herself, finishing with brass knobs and cup handles that perfectly complement her chosen shade of green

On Trend Decorating
Primarily used for chairs and inserts on 1970s sideboards, this versatile natural material is currently enjoying a style resurgence in UK homes, appearing in everything from dining room furniture to quirky cabinetry. One of its great selling points is its lightweight, pliable quality, and it also stains well – meaning it can be painted or sprayed to suit your decorating scheme. Tolerant to extreme heat and moisture, rattan is the ideal material for kitchens and bathrooms in particular; plus its purse-friendly price tag is perfect for projects on a budget.