A dormer is used to increase the headroom available for a loft conversion without having to raise the existing roof line of the property.
Dormer construction is used where the pitch of the roof is too shallow to allow agequate headroom and is often used to help with the installation of the stairs.
A dormer is built out from the roof in contrast to an ordinary loft window which is built into, and is flush with, the roof.
Because dormers are built up structures they will obviously radically alter the look of your homes exterior so a lot of though should be given to the actual design when deciding to go ahead with a new structure.
There are basically two different styles of designs – the flat roof and the chocolate box.
Not popular with students of design flat roof dormer windows are nevertheless the most common style of dormer extension because they can be installed quickly and at low cost.
The flat roof style is the one most suited to a modern property, especially bungalows, and provide a lot of extra space.
They may not be as aesthetically pleasing as a chocolate box design but can help to increase the available floor space by up to 30%.
Which is a pretty powerful argument in their favour.
This type of structure is often called the cottage style and is particularly suited to older houses and, unsurprisingly, cottages.
Chocolate box windows can look charming but they do come at a cost. Literally. They are much more expensive to install than flat roof dormer windows and they don’t add as much space.
The bottom line here is that chocolate box dormer windows look very pleasing but you may not only have to compromise on your interior design to accommodate them but must also be prepared to pay more for their installation.
Which style you pick depends on a number of factors including the age of your property, it’s location and the room available within the roof space.
As mentioned above, flat room style windows are usually more suited to newer properties though the style chosen must take into account the surrounding area.
Large flat roof structures can sometimes look ugly and, if built in an a development where they look out of place, could have an adverse effect of the saleability of your property.
But this kind of window is ideal when roof space is limited and can be particularly effective in bedroom design as they create so much more space.
If the property only has a low ridge height than a flat roofed half sized dormer may be the only solution because of the planning permission laws.
And, if planning permission is needed, only a rear facing structure will be acceptable to your local council.
When planning either type of dormer extension care must be taken to ensure that the property remains structurally sound as the addition of the window will put a lot of added stress on to rafters and joists.
Actually installing the dormer is usually straightforward with a new timber wall being added after a section of roofing is removed. Not a job that should be done in poor weather as the house will be open to the elements.
For more info see the related pages below
Structural calculations for loft conversions are of course hugely important to ensure safety and that the proposed plans meet building regulations
What is the difference between planning permission and building regulations approval for loft conversions ?
Using And Fitting Loose Fill Insulation In Your Loft