How we approach flat rooflights in Castlereagh
Flat rooflights in Castlereagh means fixed double or triple glazed rooflights for flat roofs and extensions. We cover the BT5 district and the rest of County Down, with a survey before any price is fixed.
Wind and rain off the Atlantic make upstand and flashing details important on Northern Irish roofs. Flat rooflights suit kitchen extensions, side returns and flat-roofed back rooms.
Jobs in Castlereagh are planned around access: whether the roof can be reached from the garden, whether a hoist or crane is needed, and where we can park. We check this when we measure.
What you can choose
- Square, rectangular or long-format sizes
- Solar-control or self-cleaning outer pane
- Double or triple glazing
- Insulated kerb or timber upstand built to suit
- Rain sensor if paired with an opening unit
- Slim sightlines from inside — mostly glass, little frame
- Even, top-down daylight across the whole room
Before you order: points to check
- Needs a properly formed upstand — usually at least 150 mm above the finished roof surface (check the manufacturer's figure)
- The roof membrane must be dressed up the upstand before the unit goes on
Planning and building rules for Castlereagh
Northern Ireland's householder permitted development allows rooflights within limits — no more than 15 cm projection on road-facing slopes and a 0.5 m margin from ridge, eaves and party walls. Listed buildings also need listed building consent from the council.
Technical Booklet F1 (2022) asks for replacement windows and rooflights in existing homes to reach WER Band C or a U-value of 1.6 W/m²K, assessed in the vertical position. New dwellings must average 1.40 W/m²K across windows, roof windows and rooflights.
See our building regulations guide for U-values, glazing limits and self-certification.
Guide prices for Castlereagh
These are typical supply-and-fit ranges. For an address in Castlereagh, scaffold, a hoist for heavy glass, or a new structural opening can move the figure, which is why we survey first.
| Option | Guide price inc VAT | Ex VAT |
|---|---|---|
| Large or triple glazed (1500 × 2500 mm and up) | £2,395 – £4,195 | £1,995 – £3,495 |
| Mid-size double glazed (1000 × 2000 mm) Typical | £1,675 – £2,395 | £1,395 – £1,995 |
| Small double glazed (up to 1000 × 1000 mm) | £1,195 – £1,795 | £995 – £1,495 |
What happens next
- Send the details. Postcode, rough size and a photo of the roof and room.
- Free site visit. For new installs we survey free, measure and confirm the roof detail.
- Agree the quote. You approve the specification and price before anything is ordered.
- Fit and make good. We fit, seal, test and finish the reveal, then hand over the paperwork.
Neighbouring towns
Related work in Castlereagh
Common questions
Do flat rooflights leak?
A well-fitted flat rooflight should not leak. Leaks almost always come from the upstand or membrane detailing, not the glass unit, which is why the upstand height and the way the roof covering is dressed up and under the frame matter more than the brand.
Can a flat rooflight be walked on?
Not unless it is designed as a walk-on unit with structural laminated glass. A standard flat rooflight is for light only — if the roof is used as a terrace, choose a walk-on rooflight instead.
Can you fit into my existing flat roof?
Yes. We form a new opening, trim the joists, build and waterproof an upstand and make good the ceiling. A survey confirms the joist direction and roof build-up first.
Will I need planning permission in Castlereagh?
Most rooflights on houses in Northern Ireland are permitted development under Class B, but not in a conservation area or on a listed building's curtilage.
Do I need to be at home for the survey in Castlereagh?
Yes — someone needs to let us into the room below and, where possible, show us how the roof is reached.
