What Are the Different Types of Flat Roofs?
Published by the team at Avant Garde Roofing Solutions
20+ years installing flat roofs across Northamptonshire and the Midlands
If you've got a flat roof that's seen better days, you're probably wondering what your options are. After installing flat roofs around Milton Keynes, Northampton, and the surrounding areas for over two decades, we've worked with pretty much every system going – some brilliant, others not so much.
The thing is, there's no "one size fits all" when it comes to flat roofing. What works perfectly on a factory in Luton might be completely wrong for a garage in St Albans. Here's what we've learned about the main types of flat roofing systems and where they work best.
EPDM Rubber Roofing: The Safe Bet
EPDM is basically a massive rubber sheet that we roll out over your roof. Think of it like a giant inner tube material – synthetic rubber that's designed to handle whatever the British weather throws at it.
Why it works well:
- Usually lasts 25-30 years (sometimes longer if you're lucky)
- Handles everything from January frosts to those rare 30-degree summer days
- It's one piece, so fewer places for water to sneak in
- Doesn't crack or go brittle like the old felt systems
We installed EPDM on a sports pavilion in Bedford a couple of years back. The old felt roof looked like it had been patched with everything except the kitchen sink. That EPDM system? Still bone dry, even after that awful storm we had last winter that took half the fence panels down.
The only downside is it's not great if people need to walk on it regularly – it can puncture if you're not careful.
Best for: Commercial buildings, big extensions, anywhere you want something reliable that won't give you grief.
GRP Fibreglass: Built Like a Boat
This is our go-to for most domestic jobs. We lay down fibreglass matting and resin to create what's essentially a waterproof shell over your roof. It's the same stuff they use to build boats, and boats don't leak, do they?
The beauty of fibreglass is that once it's down, it's virtually indestructible. You can walk on it, put garden furniture on it, even use it as a proper roof terrace. We did a conversion job in St Albans where the family wanted to use their flat roof as an outdoor dining area. Three years later, they're still having barbecues up there.
What makes it special:
- Completely seamless – no joints means no leaks
- You can walk on it without worrying
- Comes in different colours (though most people stick with grey)
- 30-year guarantee, but honestly, we've seen fibreglass roofs from the 90s still going strong
The only catch? It costs more upfront than other systems. But when you work out the cost over 30+ years, it's actually good value.
Perfect for: Houses, garages, anywhere you want quality that lasts.
Single Ply Membrane: The Quick Fix (In a Good Way)
Single ply is what you'll see on most new supermarkets and schools. It's large sheets of plastic or rubber that we heat-weld together on site. Sounds simple, but there's quite a bit of skill involved in getting the joints right.
The main advantage is speed. When we re-roofed that big factory in Luton, the old asphalt roof was letting water drip onto expensive machinery. We got the single ply down in three days, and the factory was back to full production without any more leaks.
Why commercial customers like it:
- Fast installation (important when you're losing money every day)
- Works well on big areas
- Light-coloured versions reflect heat in summer
- Good warranties from the manufacturers
It's not our first choice for houses though – there are better options for smaller domestic roofs.
Best suited to: Large commercial buildings, new builds, situations where time is money.
Built-Up Roofing: The Old Reliable
This is the traditional multi-layer felt system that's been around for decades. Multiple layers of bitumen felt with a mineral top sheet. Not the most exciting, but when it's done properly, it just works.
We still maintain some office blocks in Milton Keynes that have the original BUR roofs from the 1980s. With regular maintenance, they're still watertight after 40+ years. You can't argue with that track record.
Why it's still around:
- Proven to last when looked after
- Handles heavy foot traffic well
- Can install it in most weather (handy in our climate)
- Won't break the bank
The downside is it needs more maintenance than newer systems, and it's not as energy efficient as modern alternatives.
Good for: Industrial buildings, plant rooms, projects where budget is tight but you still need reliability.
Modified Bitumen: Felt's Clever Cousin
Think of modified bitumen as traditional felt roofing that's been to university. They've added polymers to make it more flexible, so it doesn't crack when temperatures drop (which happens quite a lot around here).
The improvements over standard felt:
- Stays flexible in cold weather
- Can actually heal minor punctures by itself
- Bonds really well to the roof deck
- Decent balance between cost and performance
It's particularly good for our climate because of how it handles the freeze-thaw cycles we get every winter. We use it a lot on domestic garages and smaller commercial buildings.
Works well for: Garages, small shops, refurbishment jobs where you want better than felt but don't need the full works.
Green Roofs: More Than Just Pretty
Living roofs are becoming more popular, especially in towns where space is tight. We install the waterproof layer, then add drainage, growing medium, and plants on top.
A customer in Northampton wanted to replace their garage roof with a sedum system. Apart from looking great, it's actually helped with their energy bills because of the extra insulation. Plus, the local council loved it for planning purposes.
The benefits beyond looks:
- Natural insulation keeps heat in
- Soaks up rainwater (useful given how much rain we get)
- Creates a bit of green space in built-up areas
- Can add value to your property
The main thing to check is whether your roof structure can handle the extra weight – soil and plants aren't light, especially when wet.
Worth considering for: Eco-conscious customers, urban areas, anywhere planning aesthetics matter.
So What Should You Choose?
After doing this for 20 years, here's our honest take:
For most houses: Fibreglass wins every time. Yes, it costs more initially, but divide that by 30+ years and it's actually excellent value. Plus, you can walk on it.
For big commercial buildings: Single ply if you want it done quickly with good warranties. EPDM if you want proven reliability. BUR if budget is the main concern.
For eco-minded customers: Green roofs, but make sure your structure can take the weight.
For the "just stop it leaking" crowd: EPDM. Simple, reliable, long-lasting.
The climate around here doesn't do roofs any favours – we get everything from snow and ice to those sudden downpours that seem to find every tiny gap. Whatever system you choose, proper installation is crucial. We've seen expensive materials fail because of poor workmanship, and cheaper systems last decades when installed correctly.
Getting It Right
There's no point having the best materials if the installation is rushed or corners are cut. That's why we only use our own team – no subcontractors who might not care as much about the end result.
Whatever we install comes with proper guarantees, and we'll still be here in 20 years if you need us. That's something you can't say about every roofing company.
Not sure which system would work best for your property? Give us a ring on 0800 456 1104 for a free survey. We cover Northamptonshire, Bedfordshire, Buckinghamshire, Leicestershire, Oxfordshire and Warwickshire – and we'll give you honest advice, not a sales pitch.
About Avant Garde Roofing Solutions: We've been installing flat roofs across the Midlands since 2003. Over 2,000 installations later, from tiny garages to massive commercial complexes, we're still here and still learning. We're Which? Trusted Traders and part of the Buy with Confidence scheme.