When we stripped back the old tar and stone roof on this property, we knew we were in for more than a straightforward replacement. What started as a typical fibreglass roof installation quickly became a proper restoration project - and that's exactly the kind of work we thrive on.
What We Found Beneath the Surface
The existing roll and pour tar roof had seen better days. Years of weathering had taken their toll, and the stone chippings were doing little to protect the structure underneath. As we removed the old materials, we discovered something that unfortunately isn't uncommon in older roofs: a broken rafter that had been quietly deteriorating out of sight.
This is precisely why proper roof replacement matters. A lesser contractor might have been tempted to overlay the new system on top, but that would have been a disaster waiting to happen. Instead, we bolted and braced the damaged rafter, bringing it back to full structural integrity before moving forward. Your roof's only as good as what's holding it up, after all.
Building in Proper Insulation
One of the biggest advantages of a complete roof replacement is the chance to dramatically improve your home's thermal performance. We installed a comprehensive insulation package that goes well beyond minimum requirements:
We laid down 100mm of Kingspan insulation board - one of the best performing PIR insulators on the market. On top of that, we added 100mm of Rockwool mineral wool. This dual-layer approach gives you 200mm of total insulation depth, which is exceptional for a flat roof.
The Kingspan provides outstanding thermal efficiency with minimal thickness, whilst the Rockwool adds extra insulation value plus excellent soundproofing properties. Together, they create a roof that'll keep heat in during winter, keep your home cooler in summer, and quite possibly knock a decent chunk off your energy bills year after year.
Creating the Perfect Base for Fibreglass
With the structure sound and insulation in place, we decked the entire roof using 18mm tongue and groove OSB boards. This engineered board is ideal for fibreglass work - it's stable, strong, and provides the smooth surface you need for a flawless finish.
The tongue and groove design means each board locks securely to the next, eliminating any movement or flex. This matters more than you might think. Even minor movement in the substrate can eventually cause problems with the fibreglass layer above, so getting this foundation spot-on is crucial.
The Fibreglass Installation Process
Fibreglass roofing - or GRP (glass reinforced plastic) as it's technically known - has become the gold standard for flat roofs, and for good reason. When it's done properly, you end up with a completely seamless, waterproof membrane that'll outlast practically any other flat roofing system.
Here's how we approached this installation:
Trimming and Edge Details
We fitted all the necessary fibreglass trims around the walls and roof edges. These aren't just cosmetic - they're engineered components that create neat, watertight junctions at every critical point where the roof meets a wall or drops to an edge. Getting these details right is what separates a professional job from a bodge.
Laying the Matting
The fibreglass matting went down across the entire roof area with careful attention to overlaps and coverage. This woven glass material is what gives GRP roofing its incredible strength. On its own, it's relatively flexible, but once you add the resin, everything changes.
Resin Application
We applied the first coat of resin, working it thoroughly through the matting to ensure complete saturation. As the resin cures, it chemically bonds with the glass fibres, transforming the flexible matting into a rigid, incredibly strong composite material. This is where the magic happens - you're essentially creating a custom-moulded roof in situ.
The Topcoat
Once the initial resin layer had fully cured, we applied the grey topcoat. This final layer serves multiple purposes: it provides UV protection (which extends the roof's lifespan considerably), adds another layer of waterproofing, and gives you that clean, professional finish. We opted for grey because it's practical - it doesn't show dirt as readily as lighter colours and has a modern, understated look that suits most properties.
Lead Flashings: The Traditional Way to Weather-Seal a Roof
No flat roof installation is complete without proper flashings, and we don't cut corners here. We installed new Code 4 lead flashings, 150mm wide, around each wall junction.
Code 4 lead is the right specification for this type of work - it's substantial enough to last decades but still workable enough to form properly around the roof profile. Each flashing was carefully shaped, secured into the wall, and then plugged with weather-struck cement for a completely watertight seal.
We also patinated the lead, which encourages the natural weathering process that actually protects the material over time. Lead's been used for roofing for centuries because when it's installed correctly, it just works. There's a reason traditional building methods have stood the test of time.
Sorting Out the Porch Whilst We Were At It
The main project was the roof, but we also gave the porch a proper clean whilst we had all the kit on site. A thorough jetwash brought it back to life, removing years of accumulated grime, moss and algae.
More importantly, we treated the entire porch area with anti-fungal spray after cleaning. This isn't just about appearances - moss and algae hold moisture against surfaces, which can eventually lead to deterioration. The anti-fungal treatment inhibits regrowth, so the porch should stay cleaner for considerably longer.
Before & After Transformation
Four Days from Start to Finish
Despite everything involved - the structural repair, the double insulation layer, the complete fibreglass system, the lead flashings, and the porch work - we had this project wrapped up in four days.
That's not because we rushed it. We've been doing this long enough that we know exactly how each stage needs to progress. Our team works systematically through the process, and because we specialise in fibreglass roofing, we're efficient without compromising on quality. Four days means minimal disruption for the homeowner whilst ensuring every detail gets the attention it deserves.
Twenty Years of Peace of Mind
We back this installation with a full 20-year guarantee. That's not marketing fluff - it's a reflection of our confidence in both the materials we use and the quality of our work.
Fibreglass roofing systems regularly last 30 years or more when they're installed properly. Our guarantee means that for the next two decades, you've got complete peace of mind. If anything goes wrong that's down to materials or workmanship, we'll sort it. No arguments, no small print loopholes.
Why Fibreglass Makes Sense for Flat Roofs
If you're weighing up options for a flat roof replacement, here's why fibreglass consistently comes out on top:
Completely Seamless
Unlike felt systems with their heat-welded seams or any system that relies on joins, fibreglass creates one continuous waterproof membrane. No seams means no weak points for water to exploit.
Built to Last
GRP roofing handles everything the British weather can throw at it - driving rain, freezing temperatures, baking sun, ice, snow. It doesn't crack, doesn't deteriorate, doesn't develop the problems that plague other flat roofing materials.
Minimal Maintenance
Once it's down, a fibreglass roof basically looks after itself. Keep the gutters clear, maybe give it a sweep occasionally to remove leaves and debris, and that's about it. No re-coating every few years, no patch repairs, no constant maintenance bills.
Versatile
Fibreglass works on complex roof shapes and can accommodate all the awkward details that make flat roofs challenging - upstands, outlets, odd angles. It moulds to whatever shape you need.
Fire Resistant
GRP roofing materials offer excellent fire resistance, which matters more than many people realise. In the event of a fire in a neighbouring property, your roof's performance could make a real difference.
The Professional Installation Difference
Here's the thing about fibreglass roofing: the material itself is excellent, but the final result depends entirely on the installation. We've seen plenty of fibreglass roofs that have failed prematurely, and it's almost never the material's fault - it's poor workmanship.
Common problems include inadequate surface preparation (the OSB needs to be properly fixed and clean), incorrect resin mixing ratios (which affects curing and strength), rushed application (you can't hurry the process), and poor detailing around edges and upstands (where most leaks eventually occur).
This project shows what proper installation looks like:
- We identified and fixed structural problems before they could cause bigger issues
- We installed generous insulation that'll deliver real benefits
- We prepared the substrate correctly
- We took the time to get the fibreglass application spot-on
- We completed all the weatherproofing details to a professional standard
- We stand behind our work with a substantial guarantee
The Reality of Roof Replacement
Let's be honest - nobody gets excited about needing a new roof. It's one of those essential but unglamorous home improvements that you'd rather not have to think about.
But when it's done right, a new roof is genuinely transformative. This property went from a deteriorating tar roof with hidden structural problems and poor insulation to a modern, highly efficient, completely waterproof system that won't need any attention for decades.
The homeowners now have a roof that's properly insulated (which they'll notice on their energy bills), completely watertight (no more worrying when heavy rain arrives), and professionally installed with a 20-year guarantee. That's not a bad return on investment.
When Should You Consider Fibreglass Roofing?
If any of these sound familiar, it might be time to look at a proper roof replacement:
- Your flat roof is more than 15-20 years old
- You're getting leaks, particularly after heavy rain
- The surface is cracking, blistering or deteriorating
- You can see pooling water that doesn't drain away
- You're spending money on repeated patch repairs
- Your roof is poorly insulated and costing you money
A fibreglass roof replacement isn't the cheapest option upfront, but it's almost certainly the most cost-effective over the long term. Factor in the longevity, the minimal maintenance, the energy savings from proper insulation, and the peace of mind from a decent guarantee, and the numbers start to look very different.
Getting It Right First Time
This project in particular demonstrates why experience matters. The broken rafter could have been missed by a less thorough contractor. The insulation could have been skimped on. The fibreglass could have been rushed. The lead flashings could have been substituted with something cheaper.
But none of that would have served the homeowner. They needed - and got - a professional job that'll protect their property for decades to come. Four days of focused work, proper materials, experienced tradespeople, and a guarantee that means something.
That's what a roof replacement should look like.
Final Thoughts
Roof work isn't glamorous, but it matters. Your roof is the first line of defence against everything the weather throws at your home. When it's compromised, everything else is at risk.
This fibreglass roof installation took a failing system and transformed it into something that'll still be performing flawlessly in 20, 25, even 30 years' time. The combination of structural repair, superior insulation, expert fibreglass application, and traditional lead flashings has created a roof that's genuinely fit for purpose.
If your flat roof is showing its age or causing you headaches with leaks and problems, it's worth having a proper look at fibreglass as a solution. The initial investment delivers decades of reliable performance, and when you factor in energy savings and eliminated maintenance costs, it often works out considerably cheaper than patch-and-repair approaches over the roof's lifetime.
Most importantly, you get peace of mind. No more worrying when the forecast shows heavy rain. No more emergency calls to roofers. Just a roof that quietly does its job, year after year, exactly as it should.