07460 07229724/7 Available info@stormguardroofing.ukWitney · Oxfordshire · Cotswolds Services Service Areas Our WorkReviewsAboutContactGet a Free Quote - Roofers in Witney - Roofing Services - Flat roofingRoofing services # Flat Roofing In WitneyBuilt As A Warm Or Cold DeckThat Actually Stays Dry Most failed flat roofs in Oxfordshire were never specified correctly in the first place. We build the deck, insulation, vapour control and covering as one system, then guarantee our workmanship for up to 20 years. Get my free fixed-price quote07460 072297 Approved installer for Classic Bond EPDM and Restec GRP · 9.83/10 from 159 Checkatrade reviews ## Recent flat roofing in witney work - 20 years Guarantee on GRP and EPDM flat roofs - 15 years Guarantee on felt systems - 100+ Five-star Checkatrade reviews - £5m Public liability insurance - Free Quotes and inspections ## Warm deck and cold deck, and why it matters A flat roof is not just a waterproof sheet. It is a build-up: structural deck, insulation, vapour control, and the waterproof covering on top. How those layers are ordered decides whether the roof dries out or quietly soaks itself from the inside. In a warm deck, the insulation sits above the structural deck and below the covering, with a vapour control layer underneath it. The structure stays warm, water vapour from inside the building never reaches a cold surface, and no roof void ventilation is needed. It is the build-up we specify on most replacements. In a cold deck, the insulation sits between the joists and the void above it must be ventilated so moist air can escape. It works, but only when the ventilation path is genuinely continuous and the vapour control below is intact. Filled-in vents, added downlights and a well-meaning extra layer of loft insulation are enough to break it. The commonest flat roof failure we are called to is not a hole in the covering. It is condensation inside an unventilated cold deck, producing damp patches that look exactly like a leak and reappear after every patch repair. Getting the build-up right is what makes the covering last. ### Who this is for, and when it is needed - Extensions, dormers and garages The flat roofs that cover single-storey extensions, dormer cheeks and tops, garages, porches and outbuildings across Oxfordshire. - Roofs that leak again after every repair Repeated patching that never holds usually means the problem is the build-up, not the patch. - Ponding water and soft spots underfoot Standing water and a deck that gives when walked on are signs the boards below have taken on moisture. - New extensions being built now The cheapest time to get a flat roof right is before it is covered. We specify and build new flat roofs to the correct build-up from the start. - Roofs due for a covering upgrade Old pour-and-roll felt reaching end of life can be replaced with a modern torch-on felt, GRP or EPDM system with a far longer guarantee. ## What a badly built flat roof costs you A flat roof failure is contained by nothing. Water that gets through the covering lands directly on the deck, the insulation and the ceiling below. ### What it leads to - Saturated insulation loses most of its thermal value, so the room below becomes expensive to heat and cold to sit in. - Chipboard and OSB decking swells and delaminates once wet, turning a re-cover into a full deck replacement. - Joists trapped under a soaked, unventilated deck rot from above where nobody can see them. - Condensation feeds black mould on the ceiling and around the wall junction, which returns however often it is painted over. - Water that runs along a joist can appear metres away from where it entered, so the wrong area gets repaired repeatedly. - Ponding water accelerates the breakdown of an ageing covering and adds weight to a deck that may already be sagging. ### Common mistakes - Treating a condensation problem as a leak, and paying for patch after patch that cannot fix it. - Adding insulation into a cold deck void and blocking the ventilation path that was keeping it dry. - Laying a new covering straight onto a wet or soft deck, which guarantees the new roof fails early. - Falls set to nowhere, or an outlet that sits higher than the surrounding surface, leaving permanent ponding. - Upstands and abutments taken too low, so wind-driven rain and splashback get behind the covering. We inspect the whole build-up before quoting, so the price reflects the roof you actually have, not the roof it looks like from the ground. How we work ## Our process, start to finish - Step 1 ### Free inspection We check the covering, the falls, the outlets, the upstands and the deck, and establish whether you are dealing with a leak, condensation, or both. - Step 2 ### Diagnosis and specification You get a clear explanation and a fixed-price quote that states the build-up, warm or cold deck, insulation, vapour control and covering system. - Step 3 ### Strip and deck repair The old covering comes off, wet or damaged decking and any affected timber is replaced, and falls are corrected so water reaches the outlet. - Step 4 ### Build-up and covering Vapour control, insulation and the chosen covering, felt, GRP or EPDM, are installed to the manufacturer's system, with upstands, trims and outlets detailed properly. - Step 5 ### Verification and handover The falls to the outlet are checked, the site is cleared, and you receive a before-and-after photographic report and your workmanship guarantee. What you get ## The difference it makes - ### Guarantees up to 20 years GRP and EPDM flat roofs carry a 20-year workmanship guarantee; felt systems carry 15 years. - ### The build-up is specified, not assumed Warm or cold deck is a decision we make deliberately for your roof, and it is written into the quote. - ### Approved installer status Classic Bond EPDM approved installer and Restec GRP approved installer. - ### Warmer rooms below A correctly insulated warm deck stops the heat loss and cold ceiling that come with a wet or under-insulated flat roof. - ### No annual patching Fixing the cause rather than the symptom ends the cycle of repairs that never quite hold. - ### Photographic evidence Before-and-after reports show the deck condition and the completed build-up you have paid for. ## Systems, build-ups and detailing ### Choosing between felt, GRP and EPDM High-performance torch-on felt is a multi-layer system, forgiving on complex shapes and easy to repair locally; we guarantee our felt workmanship for 15 years. GRP fibreglass cures into one seamless laminate with rigid trims and a hard wearing surface, suited to balconies and roofs that get walked on. EPDM rubber is a single sheet with almost no joints on typical domestic roofs, and it stays flexible in cold weather. There is no single best covering. Roof shape, upstand detail, foot traffic, the number of penetrations and the surrounding materials all push the answer one way or another, and we explain which we are recommending and why. ### Decking materials Plywood decking to the correct grade and thickness is the usual replacement, laid with the right fixing centres and expansion gaps. Chipboard and OSB found on older roofs are typically replaced rather than reused, because once they have been wet they never recover their strength. On concrete decks the priority is the vapour control layer and a screed or insulation fall that actually drains. ### Falls, outlets and rainwater A flat roof is never truly flat. It needs a designed fall to an outlet, achieved with firrings, tapered insulation, or a rebuilt deck. Outlets need to be set below the finished surface, big enough for the catchment, and fitted with a leaf guard where trees overhang. Where an outlet discharges into a gutter or hopper, that has to be sized and clear too, otherwise the roof backs up in exactly the storm it needs to cope with. ### Upstands, abutments and edge trims Most flat roof leaks start at an edge, not in the middle. Upstands at walls need adequate height above the finished surface, terminated properly and, where the wall is masonry, protected with lead cover flashing rather than a bead of sealant. Drip trims, raised edge trims and wall trims are part of the system, and mixing components between systems is where guarantees quietly disappear. ### Penetrations, rooflights and dormers Soil vents, flues, rooflight kerbs and dormer junctions are all points where the covering has to be formed around something. Kerbs should be built high enough to allow a proper upstand rather than dressing the covering flat against a frame. Dormer roofs need the cheeks and the top considered together, along with the junction to the main pitched roof. ### Green roofs, balconies and terraces Roofs that are walked on, or that carry decking, planters or a green build-up, need a covering chosen for that load and a way to inspect and maintain the outlets. We plan the detail so the surface can be lifted for maintenance without cutting into the waterproofing. ### Residential and commercial Commercial flat roofs, units, workshops, extensions and estate buildings, follow the same build-up logic at larger scale, with phasing arranged so the building keeps working while the roof is replaced. Questions ## Frequently asked How much does a new flat roof cost?It depends on area, access, the condition of the deck and which covering system suits the roof. We inspect and quote free of charge, and the quote is fixed price to the best of our ability with the build-up stated in writing. How long does a flat roof replacement take?Most domestic flat roofs are a short job measured in days, and we give you the timescale with the quote. Deck replacement or complex upstand detailing adds time, and we say so up front rather than after starting. What guarantee do I get on a flat roof?Twenty years of workmanship guarantee on GRP and EPDM flat roofs, and fifteen years on felt systems. Should I choose a warm deck or a cold deck?For most replacements we specify a warm deck, because it removes the ventilation dependency that causes so many cold-deck failures. Where the existing structure or a height restriction makes a cold deck the practical option, we build it with a genuinely continuous ventilation path. My flat roof is damp but I cannot find a leak, what is it?Usually condensation inside an unventilated cold deck. It behaves like a leak, it comes back after every repair, and patching the covering will not fix it. The build-up has to change. Can you re-cover on top of the existing flat roof?Only where the deck is dry and sound, and it is rarely the right answer. Covering over a wet deck traps the moisture and shortens the life of the new system. Is ponding water a problem?Standing water accelerates the ageing of most coverings and points to falls or an outlet that are not doing their job. We correct the falls as part of the replacement rather than covering over them. How long does a flat roof last?That is decided by the system, the detailing and the deck below it. Our guarantee terms, 15 years on felt, 20 on GRP and EPDM, reflect how long we are prepared to stand behind our workmanship. Do you cover emergencies on flat roofs?Yes. Storm damage and active leaks are made safe and watertight on an emergency call-out, which carries a £150 + VAT fee; any further work found is quoted and agreed separately. Which areas do you cover?Witney, Stonesfield, Woodstock, Charlbury, Chipping Norton, Burford, Banbury and across Oxfordshire, Gloucestershire and Warwickshire including the Cotswolds. Related work ## Other services we handle - ### Torch-On Felt Flat Roofing Read more - ### Seamless GRP Fibreglass Roofing Read more - ### EPDM Rubber Flat Roofing Read more - ### Roof Repairs And Leak Tracing Read moreWe cover Witney, Stonesfield, Woodstock, Charlbury, Chipping Norton, Burford and the wider area. See all roofing services, recent work, or go back to the home page. ## Get a flat roof that is specified properly Free inspection, a written build-up you can compare against other quotes, and a workmanship guarantee of up to 20 years. 07460 0722979.83/10 from 159 Checkatrade reviews · £5,000,000 public liability · Free quotes and inspections Roofing contractor based in Witney, covering Oxfordshire, Gloucestershire and Warwickshire. Pitched and flat roofing, leadwork, and Grade II listed and conservation roofing across the Cotswolds. - 07460 072297 - 01993 898807 - info@stormguardroofing.uk - 24/7 On The Line - 11 Cockshoot Close, Stonesfield, Witney, Oxfordshire, OX29 8ED ### Services - Pitched roofing in Oxfordshire - Flat roofing in Oxfordshire - Felt flat roofs in Oxfordshire - GRP fibreglass in Oxfordshire - EPDM rubber in Oxfordshire - Leadwork in Oxfordshire - Listed & heritage in Oxfordshire - Fascias & guttering in Oxfordshire - Chimney work in Oxfordshire - Roof repairs in Oxfordshire - Emergency call-outs in Oxfordshire ### Areas Covered - Roofers in Witney - Roofers in Stonesfield - Roofers in Woodstock - Roofers in Charlbury - Roofers in Chipping Norton - Roofers in Burford - Roofers in Banbury - Roofers in Stow-on-the-Wold - Roofers in Moreton-in-Marsh - Roofers in Bourton-on-the-Water - Roofers in Chipping Campden - Roofers in Shipston-on-StourGet a Free Quote About Stormguard RoofingRoofing ReviewsRoofing ProjectsContact Our RoofersPrivacy PolicyCookie PolicyTerms & Conditions© 2026 Storm Guard Roofing Limited. 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