Extension planning prep checklist
A practical prep sheet for homeowners considering a rear, side, wraparound or two-storey extension.
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Use This Before The Project Becomes Expensive
This resource is designed for early planning decisions. It helps you name the issue, record the obvious checks and avoid paying for drawings, applications or contractor commitments before the planning route is clear enough.
Good use
Print it, mark it up, save the source links and use it as a short agenda for a council, designer, consultant or builder conversation.
Not a decision
It is not a formal certificate, approval, legal opinion or replacement for checking the exact property, council and design.
Best next step
Use the project requirements generator when the checklist shows the route is still unclear or locally sensitive.
Work Through These First
- Name the extension type and whether it affects the rear, side, roof or frontage.
- Measure depth, height, width and distance to boundaries.
- Check previous additions against the original house.
- Look for conservation area, listed building, Article 4 or planning condition controls.
- Decide whether the next route is permitted development, a householder application or formal advice.
Extension planning prep checklist
Tick these off on paper or copy the text into your project notes. Keep any official links, screenshots and dates with the project record.
Project facts to collect
- Simple sketch showing projection, width, height and roof form.
- Photos of the rear, side, frontage, boundaries and neighbouring windows.
- A note of previous extensions or roof additions.
- Any known constraints from the council, title documents or past applications.
Route checks
- Check whether the design is comfortably inside permitted development limits or close to a threshold.
- Check whether neighbour impact or design character makes a fuller application more likely.
- Check whether drawings, ownership certificate, design statement or flood/heritage information may be needed.
Things Worth Avoiding
- Briefing drawings before depth, height and boundary issues are clear.
- Forgetting previous additions when calculating what remains available.
- Treating a side or wraparound extension like a simple rear extension.
- Ignoring building regulations while focusing only on the planning route.
Questions To Put To The Council Or A Professional
- What is the safest route if the extension is close to a permitted development limit?
- Which drawings and statements would the council expect if an application is needed?
- Would pre-application advice save time before a sensitive design goes in?
Official Sources Worth Opening Next
Use these as starting points and then check the relevant council page for the property. Rules, validation requirements and local controls can change by authority and site.
Pair This Planning Checklist With The Technical Evidence Route
This download helps with the planning-side decision. BuildingRegsGuide covers the building-control conversation, inspection stages and certificate evidence to keep once the project moves toward work.
Extension building regulations
Structure, insulation, drainage, fire safety, ventilation and completion evidence for extensions.
Open sister guideCompletion certificate evidence
What completion evidence is for and why it can matter later for sale, remortgage or proof.
Open sister guideClean Citation Text
Use this when sharing the resource with a neighbour, designer, builder or adviser.
General Guidance Only
This checklist is for early planning preparation and is not a design approval or formal route decision.
Before relying on a borderline route, confirm the latest position with official sources, the local planning authority or a suitable professional.