Yes, in most pitched roofs a roof window can be added, but it involves cutting the structure, so the rafters, flashing and lining all need planning before the first tile is lifted.
Adding a VELUX or similar roof window to a tiled roof means making a hole in the structure and sealing it again against weather. On tall Cotham villas and terraces, with big roof voids and sometimes loft rooms already in place, it is often possible, and it is worth understanding what the work really involves. It is a common upgrade for tall houses.
Is the roof suitable?
First we look at the roof from the ground and from inside. The pitch, the covering, the size of the loft space and the position of chimney stacks and valleys all matter. A window needs to sit where there is room to open it, to reach it and to frame it properly. Some roofs simply suit a window better than others.
Cutting the opening
A roof window needs an opening cut between rafters, and sometimes through them. Where a rafter has to be trimmed, the load is carried by doubling up the timbers either side and adding trimmers above and below. Done properly, the structure is as strong as before. This is not a job where the tiles are simply lifted and a frame dropped in. We explain how the opening will be supported before we start. Long Victorian rafters are often well suited to this.
Flashing, sealing and lining
The window is matched to a flashing kit made for the roof covering, so water is led around the frame and back onto the tiles. Inside, the opening is lined, insulated and given a vapour control layer so warm air does not condense around it. Those details are where leaks and misting begin when they are skipped. The usual sequence on an installation:
- Roof checked and window position agreed
- Tiles removed and rafters trimmed and supported
- Frame fitted with flashing kit for the covering
- Opening lined, insulated and sealed inside
- Tiles dressed back and finish checked
Rules and neighbours
Adding a window may need planning or Building Regulations checks — we advise before work starts. In a conversion or a shared building, other owners may also need to agree, since the roof is often not yours alone. It is better to settle this before anything is ordered. The decision is usually settled by a visit rather than a plan on paper.
What to ask any installer
Ask how the rafters will be dealt with, which flashing kit suits your tiles, how the lining and insulation will be finished, and how the roof is protected while open. Those answers show whether the job is understood. Call us for a proper look and we will explain your roof's options plainly. We also tell you what the roof needs around the window.
Frequently Asked Questions
Will adding a window weaken my roof?
Not if the rafters are trimmed and supported properly. The load is transferred to doubled timbers and trimmers around the opening. We assess the structure first and explain how it will be dealt with. Ask any installer to describe this in writing.
Will it leak?
A correctly fitted window with the right flashing kit for your roof covering should keep water out. Leaks usually come from poor flashing, sealing or the surrounding roof covering, not the glass. That is why the flashing kit matters.
Can it be done without a loft conversion?
Yes, a roof window can bring light into a landing, a stair or an existing loft room without a full conversion. We look at your roof space and tell you what is practical. It depends on the space.
Talk to our team about VELUX and roof window installation in Cotham
Every roof is different — the fastest way to get an accurate answer is a quick chat with our team.