Planning for a roof window

Before buying a roof window you should consider the house interior and exterior design, ergonomics and how to get most light from your windows.

What to consider to maximise light from your roof windows:

  1. The size of the roof window
  2. The number of roof windows
  3. The position of the roof windows
  4. The shape of the internal lining

Same window area = More daylight

Same window area = More daylight

Bigger windows of course admits more daylight, but it is also worth considering more smaller windows as a better overall effect can be achieved (see pictures).

Using one roof window would allow daylight to light approximately 46% of this room.

Using two roof windows with a combined total surface area of the previous window would allow daylight to illuminate approximately 48% of this room.

Four roof windows with the same combined total surface area distributed more evenly would allow daylight to illuminate approximately 65% of this room!

Correct lining for maximum light

Correct lining for maximum light

You can also admit more light into the room by using the correct lining. If the lining is vertical below the window, and horizontal above the window, you allow more light to enter the room.

Correct lining for free circulation

Correct lining for free circulation

Correctly splayed reveals allow more light to enter the room.

If incorrectly splayed, warm air is trapped and may cause condensation. When correctly splayed, warm air circulates freely around the room.

Fitting roof windows to rafters

Fitting roof windows to rafters

Before deciding on a particular size of window, the structural integrity of the roof should be considered fully. Most roofs can be adapted to take roof windows but some engineered trusses should not be cut without a proven solution. If you have any doubts which beam to cut, we recommend seeking professional advice before commencing work.

Outlook of the house

Outlook of the house

In addition to internal light and design, you should also consider what visual impact the roof windows will have on the outside of your house. Please consider the roof windows' position in relation to existing windows in the house. Then try to balance the need for internal light with the external architecture. By doing this your roof windows will look elegant from the outside and perform according to your needs on the inside.

Steeper Pitch: Longer Window

Steeper Pitch: Longer Window

A roof window should always be placed at the correct height and be of the right size to suit your specific needs.

Choosing the correct window size has to do with the roof pitch on your house. If you have a low roof pitch you need a larger roof window height to have the same view as in a house with a steeper roof pitch. A general rule is therefore that "the lower the pitch of the roof, the higher the roof window".

In addition to the size of the roof window you should also consider in which height to install the roof window. It is important that most occupants in the house have a clear view out the window.

There is no one single "correct" window size or window placement. The window should always be placed for the convenience and functionality of the users, and this can vary according to the conditions.

For the same view, a shallow pitch roof requires a taller window than a roof with a steeper pitch.

Safety during installation

Safety during installation

Wear suitable protective equipment during installation. You can normally complete the installation of a roof window from the inside of the house, and scaffolding is therefore not considered necessary. However, as with all construction there is a risk that objects might be dropped from the roof (hammer, tiles etc). We therefore recommend that you never leave any object resting on the external face of the roof, and that any area at risk should be sectioned off to minimize the risk.

It is recommended that you wear safety masks and goggles, when cutting any internal materials in the roof or when cutting tiles. Furthermore it is also suggested using temporary support battens whilst placing the window frame.