Commercial flat roofing case studies
How real commercial flat roofs are surveyed, designed and delivered. Representative scenarios are clearly labelled as modelled — we never present a modelled project as a named client.
The three commercial flat roofing projects on this page show how the same method, reading the roof from the deck up, produces very different specifications depending on the building, the loads and the falls. Before you read them, one honest note: these are modelled, representative scenarios, not named clients. This is a specialist service built on connecting building owners with accredited installers, and rather than borrow someone else's photographs or invent a client list we do not have, we have set out three realistic projects that reflect the decisions a specialist actually makes. Every figure in them, the falls to BS 6229:2025, the Part L U-value, the guarantee term, is consistent with how we specify work; none is a claim about a specific past job.
Each study starts from the same place, a survey of the deck, the build-up and the load profile, and diverges on the evidence. Together they cover the three routes most commercial roofs take: a full strip-and-recover where the insulation is wet, a liquid overlay where the existing roof is sound but tired, and a re-roof engineered for a future rooftop solar array.
3,200 m² industrial re-roof engineered for future solar PV
A 25-year-old profiled-metal-and-felt roof renewed to a single-ply warm deck, with residual structural capacity confirmed by survey so a future ballasted solar array can be added later without disturbing the new membrane.
3,200 m² · Mechanically-fixed single-ply, warm deck, structurally checked for future ballasted PV
Read case study → Modelled scenario620 m² office and plant-deck PMMA liquid overlay
A detailing-heavy 1990s office and plant deck waterproofed with a cold-applied PMMA overlay — no hot works over occupied offices, every upstand and penetration dressed seamlessly, and no strip.
620 m² · Cold-applied PMMA liquid-applied waterproofing, overlay
Read case study → Modelled scenario1,900 m² warehouse strip-and-recover to PVC single-ply
A life-expired felt roof that ponded and leaked over the picking aisles, stripped back to a sound metal deck and recovered with a mechanically-fixed PVC single-ply warm deck — occupied throughout.
1,900 m² · Mechanically-fixed PVC single-ply, warm deck with tapered insulation
Read case study →What the three studies show
A 1,900 m² warehouse strip-and-recover to mechanically-fixed PVC single-ply. A distribution warehouse with a life-expired felt roof that ponded and leaked over the picking aisles. The metal deck was sound but the insulation was saturated, so an overlay was ruled out and the roof was taken back to the deck. It was rebuilt as a warm deck with tapered insulation, falls corrected to a 1:80 finished minimum, a U-value of 0.18 W/m²K meeting the Part L thermal-element upgrade, and a 25-year single-point manufacturer guarantee. The work was phased bay by bay over about six weeks with picking continuing below, the wind-uplift fixing pattern calculated to BS EN 1991-1-4, and the roof self-certified by a CompetentRoofer-registered installer with a Building Regulations Compliance Certificate issued. It is the reference project for single-ply membrane roofing.
A 620 m² office and plant-deck liquid-applied PMMA overlay. A 1990s office block with a complex, plant-congested roof where a sound but tired single-ply membrane was reaching the end of its guarantee, and hot works over occupied offices were unacceptable. Rather than a full strip, the existing membrane was overlaid and encapsulated in cold-applied PMMA, dressing every upstand and penetration seamlessly, with localised ponding corrected at the outlets. No thermal-element renovation was triggered, so the U-value was unchanged, and a 20-year system guarantee to an LRWA-referenced specification was issued. It shows how a liquid-applied overlay can defer a capital re-roof while stopping the leaks, with no naked flame over an occupied building.
A 3,200 m² industrial unit re-roof engineered to carry ballasted solar PV. A manufacturing unit whose owner wanted rooftop solar, but whose 25-year-old profiled-metal-and-felt roof was near the end of its life. Installing an array first would have meant lifting it again within a few years, so the roof was renewed as a mechanically-fixed single-ply warm deck, structurally checked for the combined roof plus future PV dead load of roughly 15 to 25 kg/m² plus uplift. The array can now be added later without disturbing the new membrane, closing the roof-before-PV gap most roofers and solar firms leave open.
Read the how it works page for the survey-to-sign-off method behind all three, or the repair or replace page for the decision each one turned on. For a costed condition report on your own building, request a quote.