Rubber Garden Room Roof Kit – Complete 1.2mm One-Piece EPDM System with Kerb & Gutter Trims, Cut to Size

A complete one-piece 1.2mm EPDM rubber roof for a garden room, office, studio, gym or annexe, built around the way a free-standing garden building drains: a gutter drip trim along the long edge and kerb trim capping the other three, with moulded corners at all four.

The membrane is cut to your chosen size before it leaves us, so it goes on as one sheet with no on-site joining, and everything is bonded cold — no torch, no flame, no hired plant. This is the heavier 1.2mm grade, the same membrane we supply for garages and extensions, for buildings you will heat, insulate and live in.

Is this the right kit for your roof?

• ✓ A free-standing garden room, office, studio, gym, annexe or workshop with a flat or low-pitch timber deck from 2m × 2m up to 6.5m × 7m
• ✓ The roof drains to a gutter along one long edge
• ✓ A timber deck — OSB3, WBP plywood or sound boards
• ✓ You want the 1.2mm grade because the building is insulated and lived in, or the roof will carry solar panels or occasional foot traffic

Water runs to the long edge, which takes the gutter drip trim. The other three edges are capped with kerb trim, and a moulded corner sits at each of the four corners, so there is no mitring and no exposed cut edge anywhere on the roof.

Gutter on a short edge instead? Tell us when you order and we will cut the trims to suit at the same price. Built against the house? One edge needs a wall flashing rather than kerb trim — we swap it at no extra charge; the flashing and detailing guide explains the difference.

Which garden room kit? This is the 1.2mm kit. Our metal-trim kit and plastic-trim kit use the lighter 1.0mm membrane and suit sheds and summerhouses; the shed kit has no trims at all. Anything L-shaped, or with a skylight or outlet, is priced line by line in our roof kit calculator.

What is in the box

What is not included

For a standard free-standing garden room, nothing else is needed. You may want to add:

• A drain outlet if the roof drains through the deck rather than over the gutter edge
• An EPDM pipe flashing boot where a flue, soil pipe or cable passes through
• Wall flashing trim if one edge meets the house wall and you would rather add it than have us swap it in
• Walkway pads if anyone will regularly stand on the roof
• Timber and firrings to correct the falls — sourced locally, not something we ship

Choosing the right size

The size on this page is the size of the membrane, not your roof.

The rubber has to reach past the deck on every side so it can dress down over the edges and under the trims. Allow 150mm on each of the four sides. Depth is the short dimension; width runs along the gutter.

All 19 sizes are listed in the selector above, each with the deck it fits. If you fall between two sizes, take the larger one. Surplus membrane trims off in seconds; a sheet 50mm short cannot be rescued.

Size and price my roof Our calculator prices every line for any shape, including L-shaped and pitched roofs.

Specification

How it goes on

1. Prepare the deck

On a new build, check every board is fixed, the joints are flush and the falls run to the gutter edge at 1:80 or better. On a re-roof, strip the old covering, replace anything soft, punch every nail head below the surface and fill gaps over 5mm. Sweep the deck clean and let it dry completely.

2. Relax the membrane, then bond the field

Unroll the sheet with an even overhang all round and leave it 30 minutes to lose its fold memory. Fold half back and roller water-based deck adhesive onto the bare deck, stopping about 150mm short of every edge.

3. Sweep it down into the wet adhesive

Roll the folded half back into the adhesive while it is still wet — this one is not left to go tacky — and sweep it firmly from the fold outwards with a soft broom to drive the air out. Repeat for the second half.

4. Contact-bond the perimeter

Brush contact adhesive onto the dry perimeter margin and the underside of the membrane above it. Wait until both faces are touch-dry, then press the rubber down over every edge and roll it hard.

5. Fit the trims

Trim the surplus membrane to its final line, then fit the four moulded corners first and cut the straight lengths to meet them: drip trim on the gutter edge, kerb trim on the other three. Screw through the face at roughly 250mm centres and leave a 3mm expansion gap at each joint.

1.2mm or 1.0mm for a garden room?

What garden room owners say

Read all customer reviews · Rated Excellent by 1,000+ UK roofers on Trustpilot.

Delivery, dispatch and returns

• Free delivery to UK mainland addresses on every size — including the trims, which most suppliers surcharge.
• Dispatched within one working day — every membrane is cut to your size before it leaves.
• 1–3 working days on a tracked courier once dispatched. Trims travel in a separate rigid pack so they arrive straight.
• Made to measure — the membrane is cut to the size you order, so kits cannot be returned or exchanged once cut unless faulty. Faulty or damaged items are replaced or refunded in full.
• 20-year product guarantee on the membrane; BBA and fire certificates available on request.

Frequently asked questions

Can I fit this myself?

Yes, if you are comfortable working at height. Everything is cold applied, the membrane arrives as one sheet, and the trims screw on with the corners supplied. Plan a full day for a typical garden office and get a second pair of hands for positioning the larger sheets.

Which size do I need?

Measure the roof deck, add 150mm to each of the four sides, and order the kit closest to but not smaller than that figure. A 2.7m × 3.7m deck needs the 3m × 4m kit. Between sizes, go up — or WhatsApp us a photo and your measurements and we will confirm the size before you order.

Do I really need 1.2mm on a garden room?

If the room is insulated, heated and used every day, yes. The 1.2mm grade carries the BBA certificate that building control and insurers ask for, is fire tested, and has the extra thickness for a roof that may carry solar panels or be walked on for maintenance. For an unheated shed or summerhouse the 1.0mm kits are fine and cheaper.

Will the membrane have a join?

Every kit is supplied as one sheet at the size you order, so there is no on-site joining required — nothing to tape or overlap on the roof.

As with all EPDM sheet, larger sizes may contain a factory-made join formed under controlled conditions; these are covered by the product guarantee.

What exactly is included?

1.2mm EPDM membrane cut to size, water-based deck adhesive, contact adhesive for the perimeter, kerb trim for three sides, gutter drip trim for the long draining edge, four moulded external corners, a tool kit (scissors, roller set, mini roller) and all clips and pins.

Is a drainage outlet included?

No, and a standard garden room does not need one — the roof drains over the drip trim into a gutter. If your design drains through the deck into a downpipe, add a drain outlet kit, which comes with its own flashing tape and primer.

My garden room is against the house or a boundary wall

Then one edge needs a wall flashing detail instead of kerb trim: the membrane runs 150mm up the wall, is held with a termination bar and covered by a flashing. Tell us when you order and we will supply the right combination for the same price.

What colour is the membrane, and can I choose the trim colour?

The membrane is lead / slate grey, which stays cooler than black under summer sun on a room you sit in. The trims come in black, white or anthracite grey — choose above; the price is the same either way. Anthracite matches the grey bi-folds on most modern garden rooms.

Can I put solar panels on it?

Yes. Use a ballasted or frame-mounted system with a protection layer under every foot, and keep the panel feet off the trims. The 1.2mm grade is the right choice for this; ask us before fixing anything through the membrane.

How long does it take to fit?

A full day for a typical garden office: deck preparation, about two hours to bond the membrane and two more on the edges and trims. The largest sizes are a two-person day.

Does the deck have to be dry, and what weather do I need?

Yes. The deck must be completely dry and you want a dry day at 5°C or above with no rain forecast until the adhesive has cured. Water-based adhesive will not bond to a damp deck, and trapped moisture blisters the finished roof.

Can I lay EPDM over old felt?

Only if the felt is fully bonded, flat, dry and free of mineral chippings. On a garden room we would usually strip it so you can see and fix any soft boards first.

How long will it last, and is it guaranteed?

The membrane carries a 20-year product guarantee and has a life expectancy of up to 50 years. Felt on the same roof would typically need replacing three to five times over that period.

Is the membrane certified?

Yes — it is BBA certified and fire-tested to BS 476 and EN 13501. If your building control officer or insurer wants the paperwork, email us and we will send the certificates.

Does it cope with standing water?

Yes. EPDM is unaffected by ponding water. Build in a fall of 1:80 to the gutter edge anyway so the roof drains and stays clean.

Do I need a primer?

Not on sound timber decking — the water-based adhesive bonds directly to OSB and plywood. Primer is only needed for specialist details or non-timber substrates.

Can I walk on the finished roof?

For occasional maintenance in soft-soled shoes, yes. It is not a walking surface for regular traffic — fit walkway pads over the membrane if you will be up there often, and never walk on it wet or frosty.

How much maintenance does it need?

Ten minutes a year: clear leaves and debris off the roof and out of the gutter, and check the trim joints after big storms. There is nothing to re-coat or paint.

When will it arrive?

Every kit is dispatched within one working day, then 1–3 working days on a tracked courier. Delivery is free to UK mainland addresses, trims included.

What if I order the wrong size?

Tell us straight away. Every membrane is cut to your size to order, so once it has been cut it cannot be returned or exchanged unless it is faulty. If you contact us before the membrane is cut we can amend the size free of charge — which is why we would rather size it with you first.

Guides that go with this kit

• Fitting edge trims — which trim goes on which edge
• Forming corners — folding rather than cutting
• Flashing and detailing — for a wall on one side
• Drainage and falls
• Types of EPDM membrane — 1.0mm or 1.2mm?
• The full EPDM Learning Centre