1.5mm Heavy Duty EPDM Rubber Roofing Membrane – Cut to Size, Supplied as One Sheet, BBA Certified

What is 1.5mm heavy-duty EPDM rubber roofing?

1.5mm EPDM is a heavy-duty, single-ply synthetic rubber membrane for waterproofing flat and low-slope roofs. It is about 25% thicker than 1.2mm EPDM and is suited to roof terraces, balconies, commercial spans, and roofs that carry pavers, ballast or decking.

This BBA-certified membrane is cut to your measurements and supplied as one sheet, so no on-site joining is normally required. Choose from twenty widths between 0.53m and 15.24m and set the length in whole metres up to 30.5m.

The price is the same per square metre at every width. There is no cutting charge or minimum order, VAT is included, and tracked UK-mainland delivery is free. Working-day orders placed before 2pm are cut and dispatched the same day.

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 50 years and beyond. 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 roof sits in the right-hand column, the 1.2mm membrane is the normal specification and costs less. For sheds and small outbuildings, 1.0mm is enough. The thickness guide compares all three properly.

Order in three steps

1. Choose the width. Measure the deck, add 150mm to each side, and take the next stock width up from the list above — or type your exact width and we take the next one up for you.
2. Set the length in metres. Length is billed in whole metres, and the price box shows the billed size and price before you add to the basket.
3. Add to basket. Order before 2pm on a working day and it is cut and dispatched that day, arriving on a tracked courier in 1–3 working days.

Customer reviews are further down this page. Membrane only — adhesive, trims and sealant are listed separately below so you only pay for what you actually need.

Benefits of ordering from Rubber Roof UK

The same BBA-certified heavy-duty EPDM, cut to your size and backed by the checks and resources that get the order right first time.

We would far rather answer a question before you order than process a return afterwards — and cut membrane cannot be returned, which is exactly why we check first.

How the pricing works

Pick a width, then set the length in metres. 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 trade account needed, and the price you see already includes VAT. If you need a width between two on the list, you are supplied and billed at the next stock width up — the roll is only made in those widths, and the offcut cannot be sold on.

Length is billed in whole metres. Ask for 5.3m and you are charged for 6m, because that is what comes off the roll and the remainder cannot be sold on. The price box shows you the billed size before you add to the basket, so what you see is what you pay. Width is billed at the stock width supplied — the one you pick from the list, or the next one up if you enter a width in between.

Worked example: a 4.04m wide sheet at 6 metres long is 24.24 m². Multiply that by the per-m² rate and you have the delivered price — that is the whole calculation.

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 — or type your exact width and we will take the next one up for you.

Where the roof has an upstand, a kerb or a wall, add more than 150mm on that side — the membrane has to climb it as well as turn the edge. If you are between two widths, always take the larger: surplus trims off in seconds with a knife, but a sheet 50mm short cannot be rescued.

Deck width to order width, worked out for you

Measure the deck across the direction you will lay the sheet, then read off the width to order. The table already includes the 150mm allowance on each side. If the membrane also has to climb an upstand, kerb or wall on that side, add that height before you look it up.

These are the stock roll widths. Anything in between is supplied and billed at the next width up, and the same rule applies if you type your own width into the calculator above. The two widest sheets are made to order for the 1.5mm grade — email or call before ordering and we will confirm availability and lead time, or size the roof as two narrower sheets with a taped seam if that works out cheaper.

Handling a 1.5mm sheet

Heavy-duty membrane is heavier to move as well as tougher to damage. As a guide, 1.5mm EPDM weighs roughly 1.8 kg per square metre, so a 4.04m × 6m sheet is around 44 kg rolled, and a 9.15m × 10m sheet is around 165 kg. Have a second pair of hands ready when the courier arrives and when you unroll it on the deck, and unroll it with the length running along the fall so it settles flat before you fold it back for the adhesive.

Weights are a guide from the nominal membrane density and will vary slightly sheet to sheet. Large sheets are delivered kerbside, so plan how it gets from the van to the roof before delivery day.

Which thickness do you need?

1.5mm is the heavy-duty choice — terraces, balconies, commercial spans, roofs with a build-up on top, and anywhere a specifier asks for it. Step down to 1.2mm for the great majority of domestic roofs, or to 1.0mm for sheds and small outbuildings nobody walks on. Being honest about it: extra thickness buys resistance to damage, not extra waterproofing — how the sheet is bonded and detailed is what keeps water out. The thickness guide goes into the detail.

How it compares with the alternatives

Over 50 years, felt on the same roof would typically be stripped and replaced three to five times. That is the real comparison, not the price of a single covering.

What arrives

• One sheet of 1.5mm EPDM, cut square to the width and length shown in your order, with no on-site joining required
• Rolled, wrapped and labelled with the size, on a tracked courier — kerbside delivery for large sheets
• Our installation manual and install-day checklist, free to download below

Membrane only — adhesive, trims and sealant are ordered separately so you are not paying for tins you already own. Everything you need is listed below.

Life expectancy and guarantee

EPDM has a life expectancy of 50 years and beyond: the first commercial EPDM roof was laid in 1965 and is still in service, which is where that figure comes from. It is an expectation based on track record, not a guarantee period. The 20-year membrane guarantee is a separate thing. It is issued by the membrane brand owner to installers who have completed its approved training course, so it comes through your installer, not with this purchase, and a DIY installation is not covered by it. If the guarantee matters to you, use an approved installer and confirm it with them before the job. Either way you get the same BBA-certified membrane, we still check your sizes before you order, and the installation manual and install-day checklist are free. The lifespan and durability guide explains what to expect over the decades.

Specification

What else you will need

Membrane on its own does not make a roof. For a typical fully bonded job you also need:

• Water-based deck adhesive for the field of the roof, and contact adhesive for the perimeter and any upstands — the adhesives guide explains which goes where and how far a tin goes. Thicker membrane does not need more adhesive: coverage is set by the deck area, not the sheet
• 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, and essential under furniture legs, planters or plant
• Seam tape and primer only if the roof is bigger than a single sheet or you are joining to existing membrane
• An EPDM pipe boot for any flue, soil pipe or cable that passes through
• A DIY installation kit if you do not already own a seam roller, scissors and brush

Want it all priced in one go? The roof kit calculator works out membrane, adhesive, trims and corners for your exact roof.

Five mistakes that ruin a heavy-duty EPDM roof

1. Ordering the exact deck size. Without the 150mm allowance on every side there is nothing to dress over the edge, and the sheet is scrap. Measure, then add.
2. Bonding onto a damp or dusty deck. Adhesive needs a dry, swept, sound surface at 5°C or above. Sweep it twice and check the forecast before you open a tin.
3. Using deck adhesive at the edges. Water-based adhesive is for the flat field only. Anything vertical or turned over an edge needs contact adhesive on both faces, left until touch-dry.
4. Trapping air under a stiff sheet. 1.5mm is less willing to relax flat than 1.2mm. Lay it from the centre outwards, broom it hard as you go, and give it time in the sun to settle before bonding.
5. Putting a load straight onto the rubber. Pavers, planters, furniture legs and plant all need a protection layer or walkway pads between them and the membrane. Thicker rubber resists damage; it does not invite it.

Delivery, dispatch and returns

• Free delivery to UK mainland addresses on every order, whatever the size — no carriage charge added at checkout, even on the heaviest sheet.
• Same-day dispatch on orders placed before 2pm on a working day.
• 1–3 working days on a tracked courier once dispatched — track your order at any time.
• Large sheets are delivered kerbside. Have someone available to help take it off the vehicle.
• Membrane is cut to order, so once it has been cut it cannot be returned. Unopened, uncut stock items can be returned within 14 days — see the returns policy.

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?

The data sheet figure is 1.52mm against 1.2mm, so a little over 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 your width, set the length in metres, and the price shown is what you pay — VAT included, delivery free, no cutting charge.

Is the length rounded up?

Yes. Length is billed in whole metres, so a 5.3m order is charged as 6m. The price box shows the billed size before you add to the basket, so there is no surprise at checkout. Width is billed at the stock width supplied — the one you pick from the list, or the next one up if you enter a width in between.

What size should I order?

Your deck size plus 150mm on each of the four sides. Take the next width up from the list 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 to allow extra for upstands or a kerb?

Yes. The 150mm allowance covers turning the edge on a simple roof. If the membrane has to climb an upstand, kerb or wall, add that height on top on that side.

Will I need to join anything on site?

Not normally. Every order is supplied as one sheet with no on-site joining required, at the size you specify, up to 15.24m wide and 30.5m long. Larger membrane sizes may contain factory-made joins, but the membrane is delivered as one complete sheet, so no joining is normally required during installation.

What is the biggest single sheet you can supply?

15.24m wide by 30.5m long. Almost every roof, domestic or light commercial, comes in under that, which is why nearly every job is supplied as one sheet with no on-site joining required. The 12.20m and 15.24m widths are made to order in 1.5mm, so check availability with us first. For anything larger we supply two sheets and the seam tape to join them.

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.

Can I fit it myself?

Yes, if you are a competent DIYer. There is no flame, no hot works and no special tooling beyond a seam roller, a brush and a sharp knife. The differences from 1.2mm are weight and stiffness: plan a second person for any sheet over about 25 kg, and give it time to relax flat before bonding. Our free installation manual and step-by-step guide cover the rest.

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 to finish the bonded edges. Walkway pads if the roof is used. Pipe boots, seam tape and primer only if your roof has penetrations or a join.

Which adhesive goes where?

Water-based deck adhesive bonds the big flat field — it is rollered on and the membrane laid into it wet. Contact adhesive bonds anything vertical or at an edge: it goes on both faces, is left until touch-dry, then 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. Our calculator works out exact quantities including the perimeter contact adhesive.

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. Stripping back to the deck lets you find and replace soft boards before you cover them for decades.

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 us first.

Does the roof still need a fall?

Yes, a minimum of 1:80 towards the drainage edge is recommended, which is 25mm of drop for every 2m of run. Thickness does not change that. EPDM tolerates standing water, but a roof that drains dries faster, stays cleaner and lasts longer.

Does it cope with ponding water?

Yes. EPDM is unaffected by standing water at any of our thicknesses, unlike felt, which is why it suits older roofs where the falls are less than perfect.

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, so there is no wrong way up. Just keep the face that touches the deck clean and dust free.

How do I join two pieces if my roof is bigger than one sheet?

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?

EPDM has a life expectancy of 50 years and beyond, based on its track record since the 1960s. That is an expectation, not a guarantee period. The 20-year membrane guarantee is issued by the brand owner to installers who have completed its approved training course, so it comes through an approved installer rather than with this purchase, and a DIY installation is not covered by it.

Is it certified?

Yes — BBA certified, fire-tested to BS 476 and EN 13501, and rated B_ROOF(t4). Email us and we will send the full document pack: BBA certificate, data sheet, declaration of performance, both fire ratings and the installation manual, for building control or your insurer.

How is it cut — will the edges be straight?

It is cut square from the roll to the width and length shown in your order before it is packed. Small variations of a few millimetres are normal on rubber, which is one more reason for the 150mm allowance.

Can you cut an L-shape or work from a template?

We supply rectangles. For an L-shaped roof, order the smallest rectangle that encloses the whole shape and cut the notch on site — our calculator does that sizing for you and prices the trims for each edge.

Can I return it if I order the wrong size?

Cut-to-size membrane cannot be returned once cut, which is exactly why we would rather check your measurements with you first. Send the dimensions and a photo before you order.

How is it delivered and how long does it take?

Rolled and wrapped on a tracked courier, free to UK mainland addresses. Order before 2pm on a working day and it is dispatched the same day, arriving in 1–3 working days. A large 1.5mm sheet is heavy and is delivered kerbside — 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 — the full method, start to finish
• Adhesives and primers guide — coverage rates and flash-off times
• Fitting edge trims
• EPDM roofing cost guide
• The full EPDM Learning Centre