What You Need to Know Before Building a House Extension

Before building a house, you need to get two official things out of the way. The first is building regulations approval and check whether panning permission is needed. More than likely you will need both. Sometimes, you can get away with just needing the building reg. approval only of your planned extension is within certain limits.

These are covered in under roughly six parts and are related to house extension within UK only. Rules might be different within other European countries, USA and Canada. The first is area.


If the area in which you are planning to build an extension will cover more than half the original area of the garden, then you will need planning permission.


Be prepared to get planning permission if the height of your extension is more than thirteen feet (13ft) [4m] high and within two feet, six inches (6ft 2in) [2m] of a boundary irrespective of the part of the boundary.

Conservation Area

As expected, the environment comes first and preserving what cannot be easily replaced is paramount. Any building extension within an area of exceptional builderssydneyexperts natural beauty requires permission.


This is very much a key factor in any build. Any addition to the house which is going to be higher than the highest part of the house roof will require the go-ahead of planning authorities.

Listed Building

As part of cultural heritage and highly supported by the National Trust, consent must be sought and obtained for any listed buildings. In fact having extension works on any listed building requires up to five (5) types of consent depending on the extent or complexity of the house extension.


  1. Firstly and most importantly is the planning permission for building operations no matter how small.
  2. Listed building consent is needed there will be modification or demolition to a listed building.
  3. If for some reason the building constitute part of a historic monument, then scheduled monument consent will be required.
  4. Lastly, although not expected of home users, you may need advertisement content. This is only needed if advertisement and signs are going to be erected on the building.
  5. For those who wish to take on such a challenge in building an extension on a listed building, one will be pleased to know that for obtaining consent for works on the listed building that there is a considerable concession available in that the cost of alterations to listed buildings used as charities or as private residence are zero rated for VAT. More information can be obtained from the National Trust.



Any part of an extension that projects beyond the main wall of the house facing a highway or that is less than sixty five feet (65ft) [20m] from a highway requires panning consent.


If the extension is going to be an independent dwelling house then seek planning agreement first.


The most obvious and notable reason for building a house extension is to create extra living space. To guidelines laid down by the authorities stipulate that for an increase in volume of the original size of the house of the following amount (which ever is greater) that planning permission should be obtained:


  • In Scotland: General category, 28.7 sq yd [24sq m] or twenty per cent (20%)
  • Terrace houses: A ten per cent (10%) increase or sixty five and a half cubic yards (65.5 cu yd) [50 cu m], up to a maximum of one hundred and fifty cubic yards (150 cu yd) [115cu m]
  • Other houses: A fifteen per cent (15%) increase or ninety one and a half cubic yards (91.5 cu yd) [70 cu m], up to a maximum of one hundred and fifty cubic yards (150.4 cu yd) [115cu m]


Gazmen Neza is the founder of London Lofts and Contruction Ltd. (LLAC), specialist in building house extensions and loft conversions (extensions) within London.

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