What Is A Dormer Window? Planning Permission, Cost, and More

dormer window

A dormer window allows natural light to enter your property via the loft area and improves your property’s ventilation. It can be installed in different properties, including bungalows and various types of houses.

This guide helps you understand what are dormer and dormer windows and the different types of dormer windows. It also includes the difference between dormer windows and roof windows. Moreover, this article provides information about Planning Permission requirements, Building Regulations, and the cost of dormer window installation.

Understanding Dormer & Dormer Window

A dormer is a built-in structure made up of bricks or wood for enhancing your loft area’s space and head height with increased floor space. It eliminates the requirement of building another storey or extension by providing maximum space to accommodate your specific needs and requirements. Considering the aesthetic aspect, it makes your property attractive and unique with added curb appeal. It can add an extra floor to your one-storey house without building an upward extension.

A dormer window is a vertical structure that protrudes out with its own roof, having horizontal and vertical planes. Adding space in your loft area, it provides a better view of the outside area and illuminates the interior space.

Different Types of Dormer Roofs

Based on the type and shape of the property being converted, loft condition, and your requirements, there are different types of dormer roofs that you can go for, which include:

Eyebrow Dormers

These dormers curve with no sides to create a wavy shape, protruding through the roof’s slope and looking like an eyebrow.

Gable Dormers

Gable dormers are also referred to as dog house dormers because of their appearance, offering plenty of additional space. The roof’s two sloping sides meeting in the centre cover this dormer, opening in the window’s direction. These dormers are suitable for gabled houses.

Hipped Dormers

The hipped dormers project from the roof, having their own roof sloping down from all directions and creating the look of a miniature house. These dormers are usually constructed on houses with hipped roofs which have slopes in all four directions.

Rectilinear Dormers

These dormers project from the roof structure in rectilinear design, having an arch or curve-shaped roof in the segmented style.

Shed Dormers

The roof of these dormers slopes downward with a shallower angle in the direction of the main roof’s slope, featuring a single-plane roof.

dormer windows

How Does A Roof Window Differ from A Dormer?

A roof window is installed flat against the sloping roof, eliminating the requirement of any significant structural changes, such as constructing additional walls. Its installation is easy and quick as its width is in accordance with that of the rafters, requiring minimum building materials and allowing a maximum amount of sunlight to enter the room.

On the other hand, a dormer window protrudes out with its own roof and is constructed after making structural changes in the roof structure. It requires more building materials to complete the construction of the entire structure by building additional walls.

Planning Permission & Permitted Development Rights for Dormer Windows

Homeowners in the UK have the legal right to make changes or construct their properties within the Permitted Development Rights without requiring Planning Permission.

For installing dormer windows, you need to get Planning Permission approval in certain conditions, such as:

  • If the dormer window’s height exceeds the roof’s current highest point.
  • If any of the parts of the dormer are located 15cm outside your property’s existing roof slope, facing the road.
  • If any of the components of the dormer is located closer than 0.5m to the eaves, roof ridge, party wall, or verge.
  • If you intend to use any material in dormer construction that differs from the material used for constructing the rest of the property.
  • If the dormer window is glazed with obscure or opaque glazing, is non-opening, and is located on your property’s side elevation within 15m of a boundary.
  • If your property is a listed one.
  • If your property is located in a conservation area.

You should always consult your local area’s Building Control Department to confirm the approval requirements before initiating the project.

Dormer Windows & Building Regulations

You must follow building regulations while constructing a dormer in your loft area. For this purpose, you must comply with the requirements of incorporating emergency exits, structural strength and stability, and sound insulation in the newly constructed space.

Cost of Dormer Window Construction

The construction of a dormer window includes incorporating significant structural changes in the roof and purchasing the required materials, for which you need a significant cost. It also involves adding extra trimmer beams, internal and external insulation of the dormer walls, and waterproofing of the entire structure.

The overall cost of installing dormer window can range from £5,000 to £15,000 based on your project’s unique requirements and the type of dormer window you want to construct.

Table of Contents