Extending is one of the most popular ways to get more space out of a house you already like. A side or rear extension can add a bigger kitchen, a proper dining area or a room the family has been short of for years — without moving.
The question most homeowners ask first is whether they really need drawings done professionally, or whether a builder’s sketch will do. Below are four things professional drawings protect you from. If you have already decided and just want the drawings, our house extension plans and drawings page sets out what you get and what it costs.
1. A planning application that gets rejected
Not all extensions fall under permitted development, and you may need planning permission from your council to extend your home the way you want. England and Wales run separate permitted development rules, so check which set applies to your address before you assume anything is allowed.
Whenever you apply for planning permission, drawings are part of the application. It is possible to draw them yourself, but a council will refuse an application it cannot read — wrong scale, missing elevations, no site plan — and you lose the determination period as well as the fee. Drawings prepared by someone who submits them every week take that risk off the table. Across our own applications, 94% of our planning and LDC applications are approved.
2. A build that fails building control
Even where your extension does not need planning permission, you can almost guarantee it needs building regulations approval. There are two routes: a building notice, or a full plans application. We would always point you at full plans.
With a full plans application, your building regulations drawings are checked by a building control officer before anyone starts work. Getting building regulations approval up front is how you avoid finding out about a compliance problem once the walls are up, when putting it right costs real money.
3. A builder’s quote you cannot trust
However experienced your builder is, something will go wrong if there is nothing detailed to build from. Proper construction drawings give them dimensions, build-ups and junctions instead of assumptions.
That protects your budget as much as your build. A builder pricing from detailed drawings gives you a quote you can compare against another builder’s, because both are pricing the same job. Clear plans also reduce the risk of mistakes during the work, and mistakes are where unexpected costs come from.
4. Living with a layout you did not really choose
Drawings are not only for the professionals working on your project. They are the one chance you get to walk through the finished extension before it exists — where the light falls, where the doors land, whether the new kitchen actually works around the table you own.
Changes on paper are free. Changes on site are not. Seeing the layout drawn properly is how you catch the thing you would otherwise have noticed in week three of the build.
So, do you need an expert?
If your extension needs planning permission, building regulations approval or a builder’s quote you can rely on — which covers almost every extension — then yes. The drawings are doing more work than they look like they are.
You do not need a traditional architect to get them. Arkiplan works remotely across England and Wales: your home is captured with a 3D scan, the design is agreed over video calls, and we handle the council submission and the chasing. Homeowners spend £2,284 less on drawings, on average, than a traditional architect, and we have had 2,000+ homes granted permission.
When you are ready to get yours drawn up, start on our house extension plans and drawings page — that is where the packages, the process and the fixed price all live.