Dormer & Velux Loft Conversions

Welcome to Rafter Loft Conversions, this guide may be useful to understand some permitted development rules. Pictures at the bottom of the page.

The Government relaxed Permitted Development alongside the need for planning permission in the Town and Country Planning Act of 1948. Permitted Development Rights mean that you can extend your home up to a certain percentage without full planning permission,  however you must follow the many rules. In 2008 Permitted Development rights were reviewed an in a attempt to stimulate growth, Permitted Development rules were ‘relaxed’ supposedly for a three year period from 2012. The level of work you can undertake within your Permitted Development rights depends on a variety of factors including your location and the extent of work you have already carried out.

  1. Permitted Development rules any roof space created must not exceed these volume allowances of 50m3  (cubic meters) for detached and semi detached houses & 40m3  (cubic meters) for terraced houses.
  2. Loft conversions are NOT a P.D for houses on designated land.
  3. No part of the extension is to be higher than the highest part of the existing roof.
  4. Any side-facing windows must be obscure-glazed and non-opening unless the parts which can be opened are more than 1.7 metres above the floor of the room in which it is installed.
  5. An extension beyond the plane of the existing roof slope of the principal elevation that fronts a highway is NOT a P.D.
  6. Loft conversion dormer’s apart from hip to gable ones are to be set back, as far as is practicable, at least 20cms from the eaves. The 20cm distance is measured along the roof plane. The roof enlargement cannot overhang the outer face of the wall of the original house.
  7. Verandas, balconies or raised platforms are NOT a Permitted Development.
  8. Materials should be similar in appearance to the existing house.
  9.  Bats are a protected species you can NOT undertake any conversion if Bats are present. 
  10. Building Regulations must be adhered to on every loft conversion even with P.D.
  11. You have no P.D. rights if your dwelling is categorized as a listed building.
  12. No P.D. in designated area’s, i.e. Conservation Area or an area of Outstanding Natural Beauty, etc.
Here are a some absolutely ridiculous permitted DEVELOPMENT loopholes. we have not made these up!

Front Extensions, Before & After
How can this be possible? Well It’s simple, it was a mistake in the drafting of the legislation. The legislation specified limits for side extensions and specifies limits for rear extensions. It’s clear that the intention was to rule out front extensions altogether. However, the wording in the legislation only rules out front extensions where the principal elevation fronts a highway. It appears that the government simply didn’t think of the scenario where the principal elevation doesn’t front a highway. 

Outbuilding’s Before & After
This example has a width 9.0m x 17.5m length = the footprint 157.5m2 . Flat Roof Height 2.5m. The Q. is: can an outbuilding in this proportion be built under P.D. A. Oh yes it can, long as the outbuilding is required for a purpose incidental to the enjoyment of the dwelling house. i.e. swimming pool.

L Shaped Dormer, Before & After
some people may hold the view that an L-shaped rear dormer is not a loophole and should be permitted development, because it’s at the rear of the property and is unlikely to have a significant impact upon the neighbouring amenity, but the justification that is often stated for permitted development rights is to exclude “uncontentious” development. local planning authorities for which the example shown would not be directly contrary to their adopted policies and guidance. such dormers can hardly be described as “uncontentious” but as a loft company we love them.

This is similar to the above for permitted development rights, to exclude “uncontentious” development, you can not build on the front elevation of your property without Planning yet a Hip To Gable loft conversion where part of the front elevation can be. (does not make sense) again as a loft company we love this one.

Single Storey Extensions, Before & After
Really? you bet you, P.D. allows properties to add a single storey side extension (on each side) with a width up to half the width of the original house.  For example, imagine a detached two-storey house with width of 10m. the property could add a single storey side extension on each side with width 5m. This would result in a house with a two-storey part with width 10m, and with single storey parts (on each side) with width 5m (each), thus ensuring that the width of each single storey part is significantly smaller (i.e. no more than half) than the width of the two-storey part, therefore a large detached two-storey house with width 10m, which was originally built with a single storey side projection on each side with width 5m, could add a single storey side extension on each side with width 10m. This would result in a house with a two-storey part with width 10m, and with single storey parts (on each side) with width 15m (each), thus allowing the width of each single storey part to be significantly greater than the width of the two-storey part.
Boundary High Walls, Before & After
Is this possible? Of course, your Council could try to argue that the edge of this extension along the (nearside) boundary constitutes an “eaves”, which would be contrary to the 3m height limit for eaves in limitation, however the government concluded that the higher end of a pitched roof can not be taken to be “eaves”. In theory, a Council could also try to argue that the roof pitch of this extension would not be “the same as the roof pitch of the original dwelling house”, which would be contrary to condition A.3(c) again the government have concluded that where the roof of an extension would have a similar angle to the main roof, but would have a different orientation, it is possible for such an extension to comply with planning conditions.

Natural Slopping Ground, Before & After

The outbuilding shown is situated on a site that has a slope in natural ground level. This outbuilding has a flat roof, which is 2.5m above ground level when measured on the farside of the picture, and 5.5m above ground level when measured on the nearside, so this outbuilding complies with the 2.5m maximum height limit of limitation. So how does this outbuilding “comply” with the legislation, when its 5.5m height is greater than the 2.5m maximum, where the ground level is not uniform (eg if the ground is sloping), then the ground level is the highest part of the surface of the ground next to the building”.


So Which Classes of the legislation allow the extensions and alterations shown on the above picture
Class A: allows the replacement or insertion of windows (with no restrictions on the number, position, or size of the new windows) also Class A: allows the single storey side extension, Class B: allows the hip-to-gable roof extension and the full-width rear dormer, Class C: allows the re-roofing of the front roof slope (with no restrictions on materials) an allows the insertion of front Velux / roof lights (with no restrictions on the number, position, or size of the velux / roof lights), Class D: allows the erection of the front porch (with no restrictions on materials), Class E: allows the erection of the outbuilding (with no proper restrictions on the size of its footprint, or on its proximity to the main house), Class F: allows the hardstanding in the gardens (with no restrictions on the area covered, so long as the porous requirement is met), Part 2 Class A: allows the erection of walls, fences, gates, etc, Part 2 Class C: allows the painting of any part of the existing building (including the painting of previously unpainted brickwork).

With all that out of the way, if you are considering a loft conversions call our friendly team on 0800 161 3815 for a free quote, or fill out our contact form below:

Min height required for a Loft Conversion.

FAQ’sLoft Conversions – Loft GuideLoft PlansVelux Windows – FirestoneContact Us