Flat roofing specialists · Bromley, Kent & London
Natural light in the room below without the leak that usually comes with it, kerbs formed square, membranes welded up all four faces, corners properly formed. Free fixed-price quotation and a 10-year workmanship guarantee.
16 years in flat roofing · kerb detailing specialists · fully insured
Overview
Rooflight work on a flat roof is kerb and waterproofing work. We form or prepare the kerb, dress and weld the membrane up all four faces with formed corners, terminate it correctly beneath the rooflight frame, and integrate the whole detail into the surrounding roof so it behaves as one system rather than a hole with a window over it.
Homeowners adding light to an extension, kitchen or landing; builders needing the roofing element of a rooflight or lantern handled properly; and commercial clients with existing rooflights that leak, sit on failing kerbs or need reweathering during a re-roof.
During a new flat roof or extension when rooflights are part of the design, during a re-roof when existing rooflights need reweathering, and whenever an existing rooflight leaks, drips condensation or sits on a kerb that has degraded.
Rooflights are the most common leak point on flat roofs, and almost never because the glazing unit failed. They leak because the kerb was too low, the membrane was not carried high enough, corners were folded rather than formed, or the termination under the frame relied on sealant. It is a detailing problem, which is precisely the part of flat roofing we specialise in.
What happens if it is left
Rooflights sit over kitchens, living spaces and stairwells. Leaks here damage the finishes people spend the most on.
If the upstand height above the finished roof is inadequate, driving rain and ponding will get past it. No amount of mastic compensates for a kerb built too low.
Timber kerbs that stay damp degrade, which loosens the frame fixings and turns a detailing repair into a rebuild.
Poorly insulated kerbs and cold bridges cause condensation to run down the reveal. Recoating the roof does nothing for it, and the real fix is in the build-up.
Our process
We check the kerb construction, height, squareness and condition, the surrounding roof build-up, and where water or condensation is actually coming from.
We confirm kerb heights against the finished roof level, the membrane system and the trims and components needed, then issue a free fixed-price quotation.
Kerbs formed or made good, squared and made rigid, and insulated as part of the warm roof build-up so the detail does not cold-bridge.
Membrane dressed and hot-air welded up all four faces with formed corners, terminated correctly beneath the frame, then welds probed and the detail checked.
Rooflight bedded and weathered, area cleaned down, and the roofing work covered by a 10-year workmanship guarantee.
What you get
Adequate upstand height and welded, formed corners remove the mechanisms that make rooflights the usual failure point.
The roof and the kerb weathering are done by the same specialist, so there is no gap in responsibility between roofer and window fitter.
Insulated kerbs integrated into the warm roof build-up cut the cold bridging that causes water to run down reveals.
Membrane terminated neatly under the frame with the correct trims, not a bead of sealant along the top.
You get the daylight the design was for, on a roof detail that will not need revisiting.
A 10-year workmanship guarantee, priced fixed before work begins.
In detail
The upstand between the finished roof surface and the top of the kerb is the depth of water the detail can tolerate before it fails. Kerbs are frequently built to the deck level rather than the finished level, and a warm roof build-up then eats most of the height. Confirming the finished build-up depth before kerbs are constructed is the single most useful thing you can do on a rooflight project.
At each kerb corner the membrane has to be formed, cut, dressed and welded so the corner is a continuous piece of waterproofing, often with a prefabricated corner component. Butting two sheets and running sealant into the join is not a corner detail. At the top of the kerb the membrane is terminated with a compatible trim or under the rooflight frame so that no upward-facing edge relies on sealant alone.
In a warm roof, the kerb sits proud of the insulated plane and will cold-bridge unless it is insulated on its outer faces as part of the build-up. Uninsulated kerbs produce condensation on the internal reveal in winter, which homeowners understandably report as a leak. Detailing insulation up the kerb solves it.
Cutting an opening into an existing flat roof means checking the structural implications with the builder or engineer, trimming the deck, forming a new kerb at the correct height, and integrating the new membrane with the existing covering, which is only possible where the existing system is compatible and in serviceable condition. Where it is not, the sensible route is to combine the rooflight with a re-roof.
Different units have different kerb requirements, upstand heights and fixing arrangements, and walk-on glazing brings loading and slip considerations. We work to the supplier's kerb dimensions and confirm them before the kerb is built, rather than adapting the roof to a unit that has already arrived.
Commercial rooflights and roof domes on ageing units often sit on tired kerbs with degraded surrounds, and can be a fragile-surface hazard during roof works. We factor that into RAMS, and where a re-roof is happening we reweather or replace surrounds as part of the works. Asbestos awareness training matters on older commercial stock and is part of our standard approach.
Recent work
Common questions
It is quoted per project, depending on kerb condition, number of units, roof system and access. Quotations are free and fixed price as standard.
In most cases the roofing detail is at fault, not the unit. We inspect kerb height, membrane termination and corner detailing to identify the entry point before quoting.
The glazing units are usually supplied by the rooflight manufacturer or your builder. We handle the roofing side: kerb preparation, insulation, membrane detailing and weathering.
High enough to give an adequate upstand above the finished roof level, which depends on the build-up depth and the system. We confirm the figure for your roof at survey, before the kerb is built, ideally.
Often yes, subject to the structural opening being agreed with your builder or engineer and the existing covering being compatible and sound. If the roof is near the end of its life, combining the two jobs is better value.
It may be condensation from a cold-bridged kerb rather than water ingress. The two look identical from inside and are fixed in completely different ways, so it is worth having it inspected.
A 10-year workmanship guarantee on the roofing work, with manufacturer-backed guarantees available where applicable for the specified system.
Yes, including reweathering surrounds during commercial re-roofs, with RAMS provided for the works.
Bromley, Kent, London and the South East, including Orpington, Beckenham, Croydon, Dartford and Sevenoaks.
Tell us about the roof and your postcode. We will inspect it, tell you what has actually failed and give you a fixed price, backed by a 10-year workmanship guarantee.
16 years in flat roofing · Sika, Danosa and Bauder trained · fully insured · 10-year workmanship guarantee