Can I build an extension without planning permission?

Permitted development rights could allow you to build your extension without explicit planning permission. Section 55 of the Town & Country Planning Act defines ‘development’ as a building operation (structural alterations, construction, rebuilding, most demolition); significant changes of use of land and/or buildings subdivision of a building(s).

Prior to 1995 planning permission was always needed to develop. That was until permitted development came into force. Permitted development allows homeowners to extend their homes without seeking full planning permission, provided certain rules around size and styling of the development are adhered to.

Under permitted development, work is still subject to building regulations and the rules around what is permitted vary in the UK’s different regions.

Here is a run down of what you can do to your home under permitted development. It is an overview list and doesn’t cover the technical detail governing what’s OK to build and what’s not, neither does every property automatically have permitted development rights (such as flats, maisonettes, listed buildings but more about this in the next article). Therefore, it is important to get professional planning advice before putting ink on paper.

  • Porches. Keep the porch area below 3m2, roof no higher than 3m and the structure no closer than 2m from an adjacent highway.
  • Dropped kerbs. Dropped kerbs providing vehicular access from your property to the road is permissible so long as the road is an unclassified highway.
  • Internal alterations. Removing structural walls are still subject to building regulations.
  • Windows and doors. Usually permissible to the original walls. Bay windows are treated as extensions. Side-facing windows should be of frosted or obscured glass with no opener less that 1.7m from the floor.
  • Garages conversions. The garage should be integrated and the conversion must not increase the garage footprint.
  • Single storey rear extensions. Should be built from similar material to the original property and not extend passed the existing front aspect. The roof cannot exceed 4m in height or 3m at the eaves if within 2m of any boundary. Extension depth must not exceed 4m for detached properties or 3m for semi-detached, terraced or end terraced. You can double this allowance if agreed under prior approval.
  • Single storey side extensions. Same conditions as for rear extensions with the additional rule that side extensions must not be more than half the width of the original property and are not permission at all under permitted development if the property sits in a conservation area.
  • Conservatories. Same conditions apply as for single storey extensions.
  • Gates, walls and fences. Alterations are permissible so long as the property is not listed. Gates and fences should be no more than 2m high and walls no more than 1m high if next to a highway.
  • Loft conversions. Add up to 50m3 of new space on detached or semi-detached homes and 40m3 of terraced or end terraced. Don’t raise the roof height or extend passed the front roof slope.
  • Rooflights. These shouldn’t protrude more than 150mm from the roofline.
  • Double storey extensions. Keep it to the rear of the property, more than 3m deep and within 7m of the back-garden wall.
  • Basements. Technically permissible but following landmark court rulings, local authorities have become increasingly sensitive to basement developments. So always check in with the local authority first.
  • Knocking two homes into one. Doable but check in with the local authority first. You cannot split one property into two under permitted development.
  • Decking. The decked platform should not exceed 30cm in height, nor should it cover more than 50% of the garden.
  • Swimming pools. Fine, so long as the swimming pool isn’t more than 50% of the size of the garden.
  • External wall modifications. Maintaining your property (painting, pebble-dashing, cladding) is fine to do so long as the material is of similar material to the original.
  • Outbuildings. Permissible so long as the outbuilding won’t be used as living accommodation. Various conditions govern the roof height but eaves height must not exceed 2.5m. Internal size must not exceed 30m2 and the structure should be within 2m of the boundary.
  • Parking spaces. Allowed so long as the area is no more than 5m2 and if the material used is either permeable or if the driveway design allows for rainwater to run-off into a lawn or border to drain naturally. 
  • Change of use to residential. It could be possible to convert a commercial, industrial or agricultural site to residential under permitted development. However, the rules governing what you can and cannot do vary depending upon the class of development, and there are a lot of classes. In short on this one, check in with the local authority before doing anything.
  • Solar panels. Fine to install providing the panels don’t protrude more than 20cm from the host wall or roof, and the highest part of the panels sit below the highest point of the existing roof.

The rules around what qualifies for permitted development are refreshed quite regularly. What was OK to do then, may not be OK now. What you needed planning permission for then, you may not need now.

That is why it essential to apply for a certificate of lawful development (CLD). A CLD is an official document issued by the local authority proving that the planned development does indeed meet permitted development criteria so provides peace of mind that your extension is legal. You will need this piece of paper when selling your home and indeed something you insist on seeing before buying your next home.

Obtaining the certificate will take up to 8 weeks from the local authority, but that is fine because you can use this time productively. I advise using this time to start party wall process (if applicable) and hone your new extension wish list to flesh out a more focused schedule of work.

So permitted development rights could allow you to go ahead and build your extension without needing explicit planning consent, so long as certain criteria are met.

If you would like some free planning advice, get in touch with us.