Two extensions of the same size can follow completely different planning routes simply because of where they sit on the house. Rear, side and wraparound extensions are treated differently, which is why a blanket 'yes, that's permitted development' is rarely safe. Here's how position shapes the route.
In short
Where an extension sits — rear, side, two-storey or wraparound — changes the planning rules that apply. Position, height, projection, materials, your property type, designated land and any previous extensions all matter. There's no honest yes/no without checking the specific property. SC Design checks the likely route and prepares the drawings.
Not sure which route applies to your property? Send Sean your name and one way to contact you for an honest first view — with no obligation. A postcode, a few photos and a short description help if you have them, but aren't required to start.
Reviewed by Sean Corser, SC Design Wirral. Sean Corser helps Wirral homeowners with architectural design and drawing packs for extensions, loft conversions, planning and building regulations.
Last reviewed June 2026
Whether an extension is permitted development depends on a combination of factors: its type and position, height and projection, the materials, whether the property is on designated land, any previous extensions, and the type of property.
Position is one of the biggest levers — the rules are far more generous at the rear than the side or front — which is why the same footprint can be permitted development in one spot and need an application in another.
Single-storey rear extensions often have the most headroom under permitted development, within set depth, height and other limits. Side extensions are more tightly controlled — there are stricter width and height limits, and extra care is needed on designated land.
A wraparound extension combines rear and side, so it frequently goes beyond permitted development limits and needs a full planning application. Two-storey extensions have their own, stricter set of conditions again.
Flats and maisonettes don't have the same householder permitted development rights as houses, so the route is different from the outset. Conservation areas and Article 4 directions reduce or remove rights and call for sensitive design.
Previous extensions count too — earlier additions can use up the 'allowance', so what would have been permitted development on the original house may not be now. All of this has to be checked for your specific property.
Rather than guess, we look at your property, its position and history, and advise on the likely route — permitted development, a Lawful Development Certificate, or a full application — then prepare the drawings to suit.
We won't give a yes/no answer without checking the specifics, because that's how people end up building the wrong thing. The definitive position always rests with Wirral Council.
You don't need a full brief or drawings to get started — just your name and one way to contact you. The rest is optional, and you can send more whenever it suits you.
Need house extension design? We can prepare them — clear, coordinated and ready for builders and building control.
External links open in a new tab. Always confirm your specific project with the relevant authority.
All you need to start is your name and one way to contact you. A short description, postcode or a few photos help if you have them — but they're not required.