Dormer & Roof Windows
From a full dormer to a simple Velux-style roof window, built and flashed properly, and planned around permitted development rules.
Rear dormers generally don't need planning permission under Permitted Development, subject to volume limits, 50m³ of additional roof space for detached and semi-detached houses, 40m³ for terraced and end-terrace houses, provided the dormer is set back at least 200mm from the original eaves and doesn't exceed the ridge height. Front dormers almost always need full planning permission, since they typically face a highway. Side dormers need at least a 1.7m setback from the boundary to qualify as permitted development.
Simple roof windows (Velux or Fakro-style, without a dormer structure) are generally permitted development provided they don't project more than 150mm beyond the roof plane. Sherford Roofing builds dormers and fits roof windows across Plymouth and Devon, flagging the planning position for your specific project before work starts.
Our Process
Check Planning Position
We confirm whether your dormer or roof window falls under permitted development or needs full planning permission, based on position, size and property type.
Form the Opening
For a dormer, new structural supports (trimmers and rafters) form the roof opening.
Build the Dormer
Cheeks, roof and windows are built and installed, flat roof, felt, or lead-clad depending on the design.
Weatherproof & Finish
Lead flashing and soakers seal the junction, with internal finish completing the room.
Materials used for a dormer must match or be similar in appearance to the existing house under permitted development rules, worth confirming at design stage to avoid a planning issue later.
Dormer & Roof Windows FAQs
Generally no, provided it stays within permitted development volume limits (50m³ for detached/semi-detached, 40m³ for terraced houses), is set back at least 200mm from the eaves, and doesn't exceed the ridge height.
Front dormers almost always need full planning permission, since permitted development rights exclude extensions and dormers facing a highway, and most front elevations face a road.
Generally no, Velux or Fakro-style roof windows are usually permitted development provided they don't project more than 150mm beyond the existing roof plane.
Need Dormer & Roof Windows?
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