We supply and fit flat roof skylights in Clerkenwell for extensions, kitchens, garages and garden rooms. If you have a dark room under a flat roof, this page is for you. It explains the styles we fit, how they are sealed to the roof, what drives the cost and how to keep them free of leaks.
A flat roof skylight lets daylight fall straight down into the room. That makes a deep extension feel open and bright, even at the back. Our skylights are fitted by FENSA registered installers and come with a 10-year guarantee.
Flat roof skylights are part of our wider double glazing service in Clerkenwell. For every roof glazing option in one place, see our main skylights page.
Styles of Flat Roof Skylight
There are four main styles. Each one gives a different look from inside and from the garden.
- Walk-on or frameless glass. A single sheet of glass sits almost flush with the roof. From inside you see only sky. It suits modern extensions with a clean finish.
- Fixed glass on an upstand. The most common choice. The glass has a slight fall so rain runs off. The frame is thin and sits on a raised kerb.
- Opening skylights. The glass lifts on a hinge to let warm air out. These can be manual or run on a motor. Our page on electric skylights covers the controls.
- Domed or pyramid skylights. A raised top sheds water and catches more low winter sun. These suit garages, utility rooms and hallways.
If you want a bigger, framed glass roof that rises above the roof line, a roof lantern may suit you better. For a small dark room with roof space above, a sun tunnel brings in light at a lower cost.
Glass and Frame Choices
The glass does most of the work. We use sealed units with a low-E coating and a warm edge spacer. The gap between the panes is filled with argon to slow heat loss. Triple glazing is also an option for larger units.
Glass choices to think about:
- Laminated inner pane. If the glass breaks, the pieces stay stuck to a film. This is a safety must for overhead glass.
- Toughened outer pane. Strong against hail and impact.
- Solar control coating. Cuts heat and glare on south-facing roofs.
- Self-cleaning coating. Breaks down dirt so rain can wash it away.
- Tinted or obscure glass. Adds privacy where the roof is overlooked.
Frames come in aluminium or uPVC. Aluminium is slim and strong, so you see more glass. It can be powder coated in almost any colour. Anthracite grey and black are popular. uPVC frames suit domes and smaller units.
How a Flat Roof Skylight Is Fitted
Every job starts with a free survey. We check the joists, the roof build-up and the type of roof covering. We then send a written, fixed quote. The full process from survey to aftercare is on our how we work page, so here is what happens at the roof.
- We mark out the opening and cut through the roof deck.
- If the skylight spans more than one joist gap, we add trimmers to carry the load.
- We build or fit an upstand. This lifts the glass at least 150 mm above the roof so water cannot pond against it.
- We dress the roof covering up the sides of the upstand. On felt, rubber or GRP roofs, this seal is what keeps the roof dry.
- We fix the skylight to the upstand and seal the joints.
- Inside, we line the opening with plasterboard and insulation, ready for paint.
Most jobs take a day. Larger or frameless units may take two.
What Drives the Cost of Flat Roof Skylights
We do not list prices, as each roof is different. Every job gets a written, fixed quote after a free survey. You can ask for one on our get a quote page. The main cost drivers are:
- Size. Bigger glass needs a larger frame and more structural work.
- Style. Frameless and walk-on glass take more work than a framed unit.
- Glass spec. Triple glazing, solar control and self-cleaning coatings add to the cost.
- Opening or fixed. A hinge and motor add parts and wiring.
- Roof condition. An old felt roof may need repair around the opening.
- Access. Some roofs need scaffold or a tower to work safely.
Payment stages are set out in your written quote.
Planning and Building Regulations
Most flat roof skylights are permitted development. The skylight should not rise more than 150 mm above the roof plane. It must not be higher than the highest part of the roof. Rules are stricter for flats, listed homes and homes in conservation areas, so check with your council if that applies to you.
Building Regulations always apply. A new rooflight must meet the Part L limit for heat loss, which is 2.2 W/m²K for work on an existing home. Overhead glass must be safety glass. Where the work changes the roof structure, building control may need to sign it off. We tell you at the survey what is needed. As a FENSA member, we can self-certify a like-for-like replacement and give you a certificate.
Keeping Your Skylight Leak-Free
A well-fitted flat roof skylight should not leak. Most problems come from the roof around it, not the skylight itself. A few checks each year help:
- Clear leaves and moss from around the upstand.
- Check the roof covering where it meets the upstand. Look for cracks or lifting edges.
- Wash the glass with warm, soapy water. Do not use a pressure washer on the seals.
- On opening units, check the hinges and seals move freely.
- Look for mist inside the sealed unit. This means the seal has failed and the unit needs to be replaced.
Some condensation on the inside in cold weather is normal in kitchens and bathrooms. An opening skylight or an extractor fan helps clear it.
Choosing the Right Flat Roof Skylight
Start with the room. Think about how much light you want, where the sun falls and whether you need fresh air.
- For a modern kitchen extension, a large fixed or frameless unit gives the most light.
- For a bathroom or utility room, an opening unit helps clear steam.
- For a south-facing roof, add solar control glass to stop the room overheating.
- For a garden room or orangery, a lantern or a row of skylights can make a feature of the ceiling.
We will talk through the options at the survey and show you samples of the frames and glass.
Frequently Asked Questions
What maintenance do flat roof skylights require?
Very little. Wash the glass a few times a year with warm, soapy water and a soft cloth. Clear leaves and moss from around the upstand so water can drain. Check the roof covering where it meets the skylight for cracks. On opening units, run the hinge now and then so it does not stick. Self-cleaning glass needs only a rinse in dry spells.
How do flat roof skylights affect indoor temperature?
Modern sealed units lose far less heat than older skylights. Low-E glass and argon gas keep warmth in during winter. In summer, a south-facing skylight can let in a lot of heat. Solar control glass cuts this down. An opening skylight lets warm air escape from the top of the room. We help you pick the right glass at the survey.
Can more than one skylight go on the same flat roof?
Yes. Many extensions have two or three skylights in a row. This spreads light evenly across a long room. The roof joists must be able to take the openings, so we check the structure first. We may add trimmers between joists to carry the load. A row of matching units also looks neat from the garden and from upstairs windows.
What are the best materials for flat roof skylights?
For most homes, an aluminium frame with a double or triple glazed unit is the best choice. Aluminium is strong, slim and does not warp. The glass should have a laminated inner pane for safety and a low-E coating for warmth. Polycarbonate domes cost less and suit garages and outbuildings. They do not insulate as well as glass.
Are flat roof skylights suitable for the British weather?
Yes. A good skylight sits on an upstand, so rain runs off and never pools at the frame. The glass has a slight fall to shed water. Toughened outer panes cope with hail, and the frames are built to take snow loads. The key is a careful seal between the upstand and the roof covering. That is where we take the most care.
