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. planningportal.co.uk 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.