WhatCanIBuild

Already built something?

Check if your work was actually permitted development, whether you have immunity under the 4-year rule, and what your enforcement risk is.

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About the existing work

The approximate month and year the construction was finished

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Your property

2

What did you build?

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Project details

Dimensions

How many floors is your new extension? One storey = ground floor only. Two storeys = ground + first floor.
How far will the extension stick out from the back wall of your house? Measure in a straight line from the existing rear wall.
m
HouseExtensiondepth
The height from ground level to the very top of the extension roof. Stand outside and imagine measuring from the ground to the highest point.
m
max heightground
The eaves are where the roof meets the outer wall. For a pitched (sloped) roof, measure from the ground up to the point where the roof slope meets the wall — this is always lower than the ridge. For a flat roof or parapet, the eaves height is usually the same as the maximum height. Tip: stand outside and look for where the gutters sit — that's roughly eaves height.
m
PITCHED ROOFeaveseavesheightmaxheightFLAT ROOFeaveseavesheightmaxheightsame height!Eaves = where the gutter sits
The floor area of the extension, as if you looked at it from above. Width times depth. For example: 4m wide and 3m deep = 12m².
m²
widthdepthW x D = m²

Your site

Your curtilage is all the land around your house — front garden, back garden, side passages, driveway. Don't include the house itself. A typical terraced house garden is 40–80m²; a detached house might be 100–200m².
m²
total garden / curtilage areaYour house
Add up the floor area of any extensions or outbuildings already built on your land — conservatories, sheds bigger than a small tool shed, garages etc. If none, enter 0.
m²

Design choices

Your principal elevation is the front of your house — the side facing the street. Will any part of the extension be further forward than the existing front wall?
Will the outside of the extension be finished in the same materials as the existing house? For example: matching brickwork, render colour, roof tiles.