When people plan an extension they often arrive with a fixed view that a flat roof is a compromise. That view comes from a specific era of felt roofing laid without enough fall, and it does not describe what a well built flat roof does today.
What each one is good at
A pitched roof sheds water by shape. It is forgiving, it lasts a long time, and on the right building it looks like it belongs. The cost is height and space: you need the room to build the pitch, and you may lose light to the original building.
A flat roof keeps the extension low, which matters when there are windows above, when you are near a boundary, or when planning constraints limit height. It also gives you options a pitch does not, such as a roof light over the middle of a deep room.
The questions that actually decide it
- Is there a first floor window above the extension? That usually rules out a pitch.
- How deep is the extension? Deep rooms with a pitched roof can end up dark at the back.
- What do the neighbouring properties do? Matching the street is worth something when you sell.
- Do you want a roof light, and where does it need to go?
If you go flat, the detailing is the job
A flat roof lives or dies on three things: the fall, the upstands and the edges. Water must actually run to the outlet, the covering must be carried up behind whatever it meets, and the edge must be formed rather than improvised. Get those right, on a modern covering, and a flat roof is not a compromise at all.
We build both, so we have no reason to steer you towards one. Ask us to look at the plans and we will tell you what suits the building.
