An attic with sloping walls can seem larger than it is in practice. You have plenty of floor space, but due to the limited headroom, you can hardly use a large part of it. A dormer window or roof extension can change that.
Both solutions provide more usable space, but the scale of the renovation differs considerably. A dormer window makes an existing floor more usable. With a roof extension, the house can be expanded upward much more drastically.
What is the difference between a dormer window and a roof extension?
A dormer is an extension in an existing pitched roof. Part of the pitched roof makes way for a vertical facade with windows. This creates locally more headroom, daylight and usable space.
A roof extension continues. In doing so, the home is expanded at the top. For example, a rooftop extension can project above the existing roof or form an additional building volume on a flat roof.
The Environment and Planning Desk makes the same distinction: a dormer window remains part of the pitched roof, while a roof extension constitutes a larger expansion on top of the house. Furthermore, different rules may apply to both.
When is a dormer window sufficient?
A dormer is especially interesting if the existing attic is large enough, but sloping roof surfaces prevent you from using the space optimally.
By pulling a section of the roof straight up, extra headroom is created all around the dormer window. At the same time, windows are added to the new facade, making the space brighter.
A dormer window can therefore be a good choice when you:
- want to turn the attic into a bedroom;
- want to create a quiet home office;
- want more daylight on the upper floor;
- need more headroom;
- want to layout the existing floor more efficiently.
So you aren't turning the existing attic into a completely new floor, but you are making much more of the available space usable.
When do you choose a rooftop extension?
Do you need significantly more space? Then a roof extension might be more interesting. This not only modifies a small part of the roof, but allows a larger building volume to be added.
A rooftop extension is applied, for example, when space is needed for multiple bedrooms, a bathroom, or a completely new floor. Homes with a flat roof can also offer possibilities for expanding upward.
It is therefore a larger architectural intervention than a dormer window. That also means that construction, design, permits, and finishing play a greater role.
How much space do you really need?
This is the most important question when choosing between a dormer window and a roof extension.
Do you want to make one existing attic room more comfortable? Then a dormer window might be just enough. On the other hand, do you want to completely rearrange the entire top floor or add multiple full-sized rooms? Then it might be a shame to only look at a dormer window.
Therefore, do not only think about your current situation. Look a few years ahead as well. Perhaps one extra bedroom is sufficient now, but later you might also want to create a home office or an upstairs bathroom.
By looking at the big picture beforehand, you prevent yourself from carrying out a smaller renovation first and having to start all over again a few years later.
Dormer windows and rooftop extensions also differ structurally
A dormer requires modifications to the existing roof structure. With a roof extension, the consequences for the load-bearing structure can be greater, because more weight and a larger building volume are added to the home.
Therefore, it must be clear in advance how the forces will be absorbed and whether the existing home is suitable for the plan. This can influence the final shape and execution.
Matters such as insulation, roofing, window frames, interior walls, electrical systems, and any heating must also be included in the design.
A bedroom, bathroom, or entire floor?
The function of the new space has a major influence on the choices made during the renovation.
For a bedroom, sufficient daylight, ventilation, and a practical layout are important. If you want to create a bathroom, things like water pipes, drainage, and ventilation come into play, among others. With multiple rooms, you also have to think about interior walls, doors, and the walking route from the stairs.
A major renovation of the upper floor can therefore be smartly combined with other work if you are already planning to to remodel your home.
Do you need a permit?
The same rules do not automatically apply to a dormer window and a roof extension. Whether you need a permit depends, among other things, on the type of renovation, the dimensions, the location on the roof, and the rules at your location.
The Environment and Planning Portal explicitly states that a structure resembling a dormer window can sometimes still be considered a roof extension according to building regulations. Therefore, always check your specific plan via the official Permit Check.
What suits your home best?
There is no solution that is better for every home.
Opt for a dormer window especially if your existing attic is large enough, but needs more light, headroom, and usable space.
Consider a roof extension if you want to create much more living space or drastically change the upper part of the house.
Ultimately, the possibilities are determined by your home, roof structure, living requirements, and the regulations that apply at the location. Therefore, it is wise to review the whole picture before the design is finalized.
More space on top of your home?
Do you want to know whether a dormer window or roof extension is a better fit for your home? Van der Hart Timmerwerk will think along with you about the possibilities and execution from the very first idea.
We carry out construction and carpentry projects in a large working area around Amsterdam, Haarlem, and Utrecht. In doing so, we look not only at how something can be built, but especially at how you want to use the extra space later on.
Tell us what you want to achieve. Then we will look together for a suitable solution for your home.
Frequently asked questions about a dormer window and roof extension
Is a roof extension the same as a large dormer?
No. According to the Environment Desk, a dormer window is a smaller extension on a pitched roof. A roof extension is a larger addition on top of the house and can also extend above the highest point of the existing roof.
Can a rooftop extension be built on a flat roof?
Yes, a rooftop extension can indeed be used to create additional living space on top of an existing flat roof. Whether this is possible for your home depends, among other things, on the construction and the applicable regulations.
What is better for one extra bedroom?
When there is already sufficient floor space in the attic, a dormer window may be enough to create a usable bedroom. If more volume is needed or if you want to create multiple rooms, a roof extension may be a better fit.
Does the structure need to be checked for a rooftop extension?
In a roof extension, the load-bearing structure plays an important role. It must therefore be determined in advance how the extra load of the extension can be safely supported by the existing home.
