Hayes, BromleyPlatinumflatroofingltd@gmail.com - 07533 92109307753 651460 HomeAboutServices Service Areas Our WorkReviewsContact07533 921093Request Estimate Flat roofing Bromley - Flat roofing services - New builds & extensions Flat roofing specialists · Bromley, Kent & London # Flat Roofing forNew Builds & Extensionsin Bromley & London Your extension gets a properly specified, fully guaranteed flat roof that is on and watertight when your programme needs it, so the trades behind us can start on time instead of waiting on the weather. Free fixed-price quotation and a 10-year workmanship guarantee. Request your free estimate07533 921093 16 years in flat roofing · programmed around your trades · fully insured 16 years specialising in flat roofing Warm roof build-ups specified in full 10-year workmanship guarantee Fully insured, RAMS for site works Free fixed-price quotations Overview ## What New builds & extensions Involves & When You Need It ### What it is New build and extension flat roofing covers the complete waterproofing package on a new structure: vapour control layer, insulation, tapered falls where required, rooflight and kerb detailing, upstands, outlets and the finished single-ply or reinforced liquid membrane. We take the roof from bare deck to guaranteed watertight. ### Who it is for Homeowners building a rear or side extension, builders and main contractors who need a flat roofing subcontractor who turns up on the agreed day, architects and designers specifying a build-up, and developers delivering new build units with flat or low-pitch roofs. ### When it is needed As soon as the deck is down and the structure is ready to receive the build-up. On extension projects, getting the roof on early is what allows plastering, electrics, joinery and decoration to proceed to programme instead of chasing dry weather. ### Why a specialist matters A new roof is the one chance to get the build-up right before everything below it is finished. Threshold heights, rooflight kerbs, upstand heights against the existing house, outlet positions and falls all have to be resolved before the membrane goes on, and once the ceilings, plaster and flooring are in, correcting any of them is expensive. Because flat roofing is all we do, we raise those details at survey rather than discovering them on the day. What happens if it is left ## Flat Roof Problems Do Not Stay the Same Size ### A late roof stops the whole programme Every trade after the roof is waiting on it. A slipped roofing date pushes plaster, electrics and decoration, and open structures take weather damage while they wait. ### Kerb and threshold heights fixed too low Rooflight kerbs and door thresholds set without allowing for the finished build-up leave inadequate upstand height, which is a permanent weak point that shows up in the first heavy rain. ### Falls designed on paper, not built Roofs built dead flat with no worked-out fall to outlets pond immediately, and standing water on day one shortens the life of the covering. ### Water damage to new finishes A leak into a newly finished extension damages plaster, joinery, flooring and decoration; the roofing repair is the cheap part of that bill. ### Common mistakes we are called in to correct - Leaving the roof specification undecided until the deck is down - Setting rooflight kerbs and door thresholds without allowing for warm roof depth - Splitting the roof package between trades so nobody owns the detailing - Choosing a covering on price without checking it suits the deck and insulation - Assuming the builder's general roofer will detail single-ply the way the manufacturer requires Our process ## Five Steps from First Call to Guaranteed Roof - 01 ### Inspection & pre-start review We review drawings or visit site, check deck type, falls, outlet positions, kerb and threshold heights, and flag anything that needs resolving before the build-up starts. - 02 ### Specification & fixed price A free, fixed-price quotation naming the vapour control layer, insulation, tapered scheme if required, membrane system and all detailing components. - 03 ### Programmed installation We agree a date with you or your main contractor and work to it, coordinating with carpenters, rooflight suppliers and scaffolders so the roof is not held up or holding others up. - 04 ### Detailing, testing & sign-off Upstands, kerbs, outlets and abutments detailed to the manufacturer's standard, welds probed or liquid coverage verified, drainage tested. - 05 ### Completion & guarantee Roof handed over clean and watertight with a 10-year workmanship guarantee, and manufacturer-backed guarantee options where applicable. What you get ## The Practical Difference a Specialist Makes ### On programme Dates agreed and kept, so the trades behind the roof are not left standing. ### One responsible trade Deck to finished membrane, including all details and rainwater terminations, handled by one specialist, no gaps between subcontractors. ### Details resolved early Kerb, threshold and outlet issues get raised before they are built in, when fixing them is free. ### Modern warm roof performance Fully specified warm roof build-ups with continuous vapour control and correctly fixed insulation. ### Clean, contemporary finish Welded single-ply gives extensions the flat, sharp finish that suits modern flat-roof architecture, in a choice of membrane colours. ### Guaranteed from the start A 10-year workmanship guarantee on a brand-new roof, priced fixed before we begin. In detail ## New builds & extensions: Materials, Methods & Variations ### Working with builders and main contractors On contractor-run projects we work to your programme, provide RAMS for our works, coordinate with the scaffold and attend when the deck is genuinely ready. Where the roof is being handed to us mid-build, we confirm deck condition and levels before starting so responsibility for what is under our membrane is clear on both sides. ### Build-ups for new flat roofs Most new flat roofs are built warm: vapour control layer sealed to the deck, insulation above, waterproofing on top. Board thickness is set by the thermal performance the project requires, and tapered schemes are designed where the structural deck is level and fall has to be created within the insulation. The full build-up is named in the quotation so it can be checked against the drawings. ### Rooflights, lanterns and kerbs Rooflights are the most common source of leaks on new extensions. Kerbs need to be built to a height that gives adequate upstand above the finished roof level, square and rigid, and the membrane needs to be dressed and welded up all four faces with formed corners before the glazing unit lands. We coordinate with the rooflight supplier's dimensions rather than assuming them. ### Junctions with the existing building Extension roofs almost always abut existing brickwork or render. That junction needs a proper upstand, termination trim or chased detail, and consideration of where water is coming from above: including the main roof's rainwater discharge. Dressing a membrane up a wall and sealing the top with mastic is not a termination. ### Drainage, outlets and rainwater goods Outlet size and position are checked against the roof area and the fall design, with overflow provision considered so a blocked outlet does not load the deck. We can also install the fascias, soffits, trims and guttering that finish the roof edge, so the water path from membrane to downpipe is built by one trade. ### Domestic extensions versus new build sites Domestic extensions are short, detail-heavy jobs where the priority is getting the roof on quickly and neatly around an occupied house. New build and development sites are about repeatability, phasing and documentation: RAMS, agreed sequencing, and photographic records where the client or funder needs them. We work in both, from Bromley across Kent and London, and nationwide on larger commercial schemes. ### Related services - Warm roof systems - Rooflights - Single-ply roofing ### Where we work - Bromley - Kent - London - Buckinghamshire - Dartford - Orpington - Sevenoaks - Beckenham - Croydon - NationwideSee all service areasAll flat roofing servicesPlatinum Flat Roofing homeContact us Recent work ## New builds & extensions, Completed Projects Common questions ## New builds & extensions, Your Questions Answered How much does an extension flat roof cost?Each roof is quoted individually on its size, build-up, detailing, rooflights and access; we do not use 'from' prices. Quotations are free and fixed price as standard. How quickly can you fit our roof in?It depends on current workload, and we will give you a straight answer at quotation rather than a date we cannot hold. Once a date is agreed, we work to it. Can you work directly with our builder?Yes: much of our new build and extension work is with builders and main contractors. We provide RAMS for site works and coordinate with the programme. Which system will you use on a new extension?Usually a warm roof build-up finished in hot-air welded single-ply, Sika, IKO Armourplan, Danosa or Bauder, or a reinforced liquid system where the roof is small and detail-heavy. The choice is named in the quotation. Do you install rooflight kerbs?We detail and waterproof kerbs as part of the roof, and we will confirm the kerb heights needed before they are built so the upstand works. Glazing units are supplied and set by the rooflight supplier or your builder. What guarantee is provided on a new roof?A 10-year workmanship guarantee, with manufacturer-backed guarantees available where applicable depending on the specified system and project. Can you do the fascias and guttering too?Yes. Fascias, soffits, trims and rainwater goods can be included so the roof edge and drainage are finished by the same team. Do you work outside Bromley and Kent?We cover Bromley, Kent, London and the South East as standard, and work nationwide on larger commercial projects. When should we book the roof?As early as possible. Booking at design or first-fix stage means the kerb heights, thresholds and outlet positions get checked before they are built in. ## Get a Free Fixed-Price Quote for New builds & extensions 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. Request your free estimate07533 921093 16 years in flat roofing · Sika, Danosa and Bauder trained · fully insured · 10-year workmanship guarantee Single-ply and liquid-applied flat roofing specialists serving Bromley, Kent, London and the South East. ### Services - Single-ply roofing - Liquid waterproofing - Refurbishments & remedial works - Warm roof systems - New builds & extensions - Balconies & walkways - Rooflights - Fascias, soffits & guttering ### Service areas - Bromley - Kent - London - Buckinghamshire - Dartford - Orpington - Sevenoaks - Beckenham - Croydon - Nationwide ### Contact - Hayes, Bromley - 07533 921093 - 07753 651460 - Platinumflatroofingltd@gmail.com - @platinumflatroofingltdCompany No. 17149842Fully insured · 10-year workmanship guarantee © 2026 Platinum Flat Roofing Ltd. All rights reserved.ReviewsPrivacy policyTerms & conditions Call nowFree quote