Description
The heavy-duty EPDM rubber roofing membrane — around 25% thicker than the standard 1.2mm — cut to your exact size and supplied as one continuous sheet. It is the specification for roofs that get walked on, commercial spans, and decks where extra toughness earns its keep. Twenty widths from 0.53m to 15.24m, any length up to 30.5m, bonded cold with no torch and no flame.
Do you actually need 1.5mm?
We would rather sell you the right membrane than the dearest one. 1.5mm and 1.2mm are equally waterproof — they are the same rubber, both BBA certified, both with a life expectancy of up to 50 years. The extra thickness buys resistance to punctures, tearing and foot traffic. It does not make a roof more watertight; how the sheet is bonded and detailed decides that.
If your project is a standard extension, garage, garden room or dormer that nobody walks on, the 1.2mm membrane is the normal specification and will cost you less. For sheds and small outbuildings, 1.0mm is enough. The thickness guide compares all three properly.
How the pricing works
Pick a width, then set the quantity to the number of metres of length you need. Every width works out at exactly the same rate per square metre — a 0.53m offcut and a 15.24m sheet cost the same per m². No cutting charge, no minimum order, no surcharge for awkward dimensions, and the price shown already includes VAT.
What size should you order?
Measure the roof deck, then add 150mm to each of the four sides so the rubber can dress down over every edge. Take the next width up from the list and round the length up to whole metres.
Add more than 150mm where the roof has an upstand, kerb or wall — the membrane has to climb it as well as turn the edge. Between two widths, always take the larger: surplus trims off in seconds, a sheet 50mm short cannot be rescued.
Work out my size and price Handles L-shaped and pitched roofs, skylight voids, adhesives and trims.
Specification
| Material | EPDM (ethylene propylene diene monomer) synthetic rubber, single ply |
| Thickness | 1.5mm — approximately 25% thicker than the standard 1.2mm |
| Colour | Slate grey |
| Widths available | 20 widths: 0.53, 1.03, 1.53, 2.03, 2.53, 3.05, 3.53, 4.04, 4.57, 5.05, 5.55, 6.10, 6.55, 7.07, 7.62, 8.05, 8.55, 9.15, 12.20 and 15.24m |
| Maximum single sheet | 15.24m wide × 30.5m long — supplied in one piece, no site joining |
| Price basis | Per square metre, identical rate across every width. VAT included. |
| Certification | BBA certified, certificate no. 19/5670. Fire performance tested to BS 476 and EN 13501. Certificates on request. |
| Life expectancy | Up to 50 years |
| Guarantee | Manufacturer product guarantee — ask us for the current terms |
| Temperature range | Remains flexible from −40°C to +120°C |
| Standing water | Unaffected by ponding water |
| UV and ozone | Stable — will not crack, peel, split or need re-coating |
| Suitable decks | OSB3, WBP plywood and other sound timber decking; more forgiving than 1.2mm over slightly uneven substrates |
| Recommended fall | Flat and low-pitch roofs; minimum fall of 1:80 recommended |
| Fixing method | Fully bonded, cold applied — no heat or naked flame |
How it compares
What else you will need
- Water-based deck adhesive for the field and contact adhesive for the perimeter and upstands — the adhesives guide covers which goes where and coverage rates
- Drip trim for the gutter edge and kerb trim elsewhere, with a moulded corner at every turn — see all trims
- Lap sealant for finishing bonded edges
- Walkway pads — worth it even on 1.5mm if the roof takes regular traffic
- Seam tape and primer only if the roof exceeds a single sheet or you are joining to existing membrane
- An EPDM pipe boot for any flue, soil pipe or cable through the roof
Free downloads — no email address needed
Our own installation manual and a one-page checklist for the roof.
Delivery, dispatch and returns
- Free delivery to UK mainland addresses on every order, whatever the size.
- Same-day dispatch on orders placed before 2pm on a working day.
- 1–3 working days on a tracked courier once dispatched.
- Membrane is cut to order, so once cut it cannot be returned. Uncut stock items can be returned within 30 days.
Frequently asked questions
Is 1.5mm more waterproof than 1.2mm?
No, and we would rather be straight about it. Both are the same rubber and both are completely waterproof. The extra thickness buys resistance to punctures, tearing and foot traffic. Leaks come from poor bonding and poor detailing, never from the sheet being too thin.
How much thicker is it, really?
1.5mm against 1.2mm is about 25% thicker. You can feel the difference handling it, and it is noticeably more forgiving over a slightly uneven deck.
When should I choose 1.5mm?
When the roof gets regular foot traffic — a terrace, balcony or roof garden — on commercial or large-span roofs, where pavers, ballast or decking sit on top, where there is impact risk from overhanging trees or ladders, on older or uneven decks, or when a specifier has asked for it by name.
When is 1.2mm enough?
For the great majority of domestic roofs: extensions, garages, garden rooms, dormers and porches that are only walked on for maintenance. It is the standard UK specification and it costs less.
How is the membrane priced?
By the square metre, at the same rate for every width. Choose a width, set the quantity to the metres of length you need, and the price shown is what you pay — VAT included, delivery free, no cutting charge.
What size should I order?
Your deck size plus 150mm on each of the four sides. Take the next width up and round the length to whole metres. A 3.5m × 5m deck needs roughly 3.8m × 5.3m, so order the 4.04m width at 6 metres.
Do I need extra for upstands or a kerb?
Yes. The 150mm allowance covers turning the edge. If the membrane must climb an upstand, kerb or wall, add that height on top on that side.
Will there be a join or seam?
No. Every order is one continuous sheet at the size you specify, up to 15.24m wide and 30.5m long.
What is the largest single sheet you can supply?
15.24m wide by 30.5m long. Almost every roof, domestic or light commercial, comes in under that.
What colour is it?
Slate grey, the same as the 1.2mm. It weathers to a slightly matt finish rather than fading to another colour.
Can I lay pavers, decking or a green roof on top?
Yes, and this is exactly where 1.5mm earns its price. Use a protection layer or walkway pads between the membrane and anything laid over it, and never let anything sharp bear directly on the rubber. Check the structure can take the load before you build up.
Can I use it on a roof terrace or balcony?
Yes. For regular foot traffic, specify 1.5mm and add walkway pads or a proper deck build-up over the membrane rather than walking on the rubber itself.
What else do I need to buy?
At minimum water-based deck adhesive for the field and contact adhesive for the perimeter and upstands. Most roofs also want edge trims with corners and lap sealant. Pipe boots, seam tape and primer only if you have penetrations or a join.
Which adhesive goes where?
Water-based deck adhesive bonds the flat field — rollered on, membrane laid into it wet. Contact adhesive bonds anything vertical or at an edge: both faces, left until touch-dry, then it grabs instantly. Never swap them.
Does the thicker membrane need more adhesive?
No. Adhesive coverage is set by the area of deck, not the thickness of the sheet. A 5-litre tin of water-based deck adhesive still covers roughly 20 m².
Is it harder to install than 1.2mm?
Marginally. It is heavier to handle and a little stiffer to dress into corners, so it is worth having a second pair of hands on a large sheet. Everything else about the method is identical.
Do I need a primer?
Not for bonding to sound timber decking. Primer is for detail work — bonding tape, flashings or patches to the membrane surface.
Can it be laid over an existing felt roof?
Sometimes, but stripping is better. Overlaying only works if the old felt is fully stuck down, flat, dry and free of mineral chippings.
What can it be bonded to?
Sound timber decking — OSB3, WBP plywood or planed board. Concrete, metal and insulation boards are possible but need different preparation, so ask first.
Does the roof still need a fall?
Yes, a minimum of 1:80 towards the drainage edge, which is 25mm of drop per 2m of run. Thickness does not change that.
Does it cope with ponding water?
Yes, EPDM is unaffected by standing water at any of our thicknesses.
Can it be laid in cold or wet weather?
The membrane is unaffected, but the adhesives are not. You need a dry deck, a dry day and 5°C or above, with no rain forecast until the adhesive has cured.
Which side goes up?
Membrane of this type is the same on both sides. Keep the face that touches the deck clean and dust free.
How do I join two pieces?
Overlap by 75mm, prime both faces of the overlap and join with seam tape rolled hard from the centre out. Plan the seam across the fall and never through a detail. The installation guide covers it step by step.
How long does it last, and is it guaranteed?
A life expectancy of up to 50 years, with a manufacturer product guarantee — ask us for the current terms and we will send them with the certificates.
Is it certified?
Yes — BBA certified under certificate no. 19/5670 and fire-tested to BS 476 and EN 13501. We will send the paperwork if building control or an insurer asks for it.
Can I return it if I order the wrong size?
Cut-to-size membrane cannot be returned once cut, which is why we would rather check your measurements first. Send us the dimensions and a photo before you order.
How is it delivered?
Rolled and wrapped on a tracked courier, free to UK mainland addresses. Order before 2pm on a working day for same-day dispatch, arriving in 1–3 working days. A large 1.5mm sheet is heavy — have someone available to help take it off the vehicle.
Guides that go with this membrane
- Thickness guide — 1.0mm, 1.2mm and 1.5mm compared
- How to install EPDM roofing
- Adhesives and primers guide
- Fitting edge trims
- The full EPDM Learning Centre
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