Dormers typically must meet certain requirements regarding thermal efficiency, emergency escape routes, and fire and electrical safety. In some areas, dormers added to the rear of your home might not need building regs approval. Always double-check local rules and regulations with your local government to be sure. Make sure you’re following building code and bylaws with dormers, you have to be very very careful with zoning bylaws.
For example, front dormers may not be allowed to extend past the building line formed by the fronts of neighboring houses along the street. Designs larger than the size of a porch or that drastically change the character of the house may also be prohibited. Ultimately, the decision to grant permission for any dormer is subjective and is in the hands of your local building control surveyors. Regulations vary from area to area, so do your research on your local government’s website to find out about specific requirements and prohibitions.
Note that this is the height from the floor to the middle ceiling joist of the dormer.
The architectural features of your home can also guide the width of the dormer. For example, a dormer that’s a little narrower might look best on a house with very classical features, while one that’s a little wider might look better on a house with more horizontal design features. Hiring an architect to help you with the design is the best way to make sure you get the dimensions right.
Keep in mind that in order to do this project yourself, you should be familiar with roofing, framing, and general construction. Otherwise, get a professional to do it for you. Get some large waterproof tarps to cover the opening in your roof if it rains. Secure them over the opening by weighing them down with pieces of lumber.
You usually have to remove at least 2 rafters to add a small dormer.
Use a 2 in (5. 1 cm) by 6 in (15 cm) or a 2 in (5. 1 cm) by 8 in (20 cm) piece of lumber for the ceiling joist.
If you’re going to install a window in your dormer, frame an opening for the window using shorter vertical and horizontal studs.
Note that you only need angled rafters if you’re making a dormer with a gabled roof. If you’re building a flat-roofed dormer, install horizontal rafters.
You can also use OSB boards instead of plywood.
Adding a dormer is a good time to replace the rest of your roofing as well, so all the materials match and are in equally as good condition.
Talk to a local roofer to find out more specific prices for building dormers in your area.
Dormers are a very cost-effective way to add functionality and value to your home, especially when adding a full additional floor or extension isn’t permitted or isn’t within your budget.
