Green Roof Root Barrier Membrane – HDPE Woven-Reinforced, 0.5mm–0.65mm, 7 Roll Sizes

Skip the root barrier on a green roof and sedum roots will eventually find every seam, fixing point and upstand in the waterproofing beneath them — by then the membrane is buried under substrate and the only fix is stripping the roof back down. This HDPE root barrier goes in once, before the growing layer goes on, and takes that risk off the table for good.

What it does

A dedicated root barrier sits directly above the waterproofing membrane (typically EPDM on a flat roof) and below the drainage/reservoir layer and growing substrate. It stops roots, rhizomes and fine root hairs from a sedum blanket, wildflower mix or intensive planting scheme working their way down into seams, laps and penetrations in the waterproofing — the single most common cause of green roof leaks that only show up years after installation, once the plants are established and the roof is no longer easily accessible.

Key benefits

• HDPE-based construction with triple-coated LDPE layers, purpose-built to resist root penetration rather than repurposed damp-proofing
• Twin thermally-bonded woven reinforcement scrim runs through the sheet for tear and puncture resistance during installation and backfilling
• Passed the DD CEN/TS 14416:2005 root penetration test — the recognised European test method for green roof root barriers
• 4,500N puncture resistance to EN ISO 12236, so it stands up to stone, grit and tool contact during the drainage and substrate stages
• UV stabilised for the exposed period before it's covered, and CE marked
• Supplied in widths and pack sizes that scale from a small garden room roof to a full commercial trade order

Where it's used

Root barrier belongs in the build-up under any planted or sedum roof — garden rooms, garages, extensions, summerhouses, and larger intensive or extensive green roof projects. It's laid over the waterproofing layer (see our EPDM roofing membrane for that layer) and beneath the drainage board, so it belongs on the shopping list alongside our Green Roof Drainage & Water Reservoir Board — order both together and you've got the two layers that sit between the waterproofing and the substrate.

Specification

Sizes & options

Seven sizes are available, from a small 5m² roll for a shed-sized roof up to full 500m² trade packs for commercial work:

• 1m x 5m (5m²)
• 1m x 10m (10m²)
• 1m x 25m (25m²)
• 1m x 50m (50m²)
• 2m x 25m (50m²)
• 1m x 25m × 10 Rolls – Trade Pack (250m²)
• 2m x 25m × 10 Rolls – Trade Pack (500m²)

Always order enough to allow roughly 10–15% extra for overlaps at joints and turning the barrier up any perimeter upstand.

Installation & usage guidance

Lay the barrier over a clean, dry waterproofing layer with no sharp debris trapped underneath. Overlap adjoining sheets by at least 100mm and run the overlap so water sheds correctly toward the outlets. Turn the membrane up any upstand or kerb detail so there's no gap for roots to bypass at the perimeter. Once laid, keep foot traffic and sharp tools to a minimum until the drainage board is down, and don't leave the barrier exposed to prolonged UV or foot traffic longer than necessary before the rest of the build-up goes on. This product isn't glued or welded at the laps in the way a waterproofing membrane is — the overlap and the weight of the layers above hold it in place, so installation is straightforward for anyone comfortable building a green roof build-up.

A separate protection fleece layer is sometimes added above the root barrier (and below the drainage board) on roofs with a coarser drainage product or sharper substrate, to spread point loads and add an extra layer of puncture protection — worth considering on larger or heavier-use roofs, though it isn't required on every build-up.

Ordering

Choose the size that matches your roof area with the 10–15% overlap allowance included, or order one of the 10-roll trade packs if you're fitting multiple roofs or ordering for a contract. All sizes ship as rolls and are available to order now.

FAQs

Does this replace the waterproofing membrane?
No. Root barrier is an additional protective layer that sits on top of the waterproofing (such as EPDM) — it doesn't waterproof the roof on its own.

Do I need to tape or weld the joints?
No welding is required. Overlap adjoining sheets by at least 100mm in the direction water will run, so laps shed water rather than trap it.

How long does root barrier last?
The manufacturer states an indicative life expectancy of 50+ years once installed correctly and permanently covered by growing medium. That's a manufacturer figure rather than an independently certified guarantee, and real-world life depends on correct installation and the build-up above it.

Can I use this with any waterproofing system?
Yes — it's designed to sit above any suitable flat roof waterproofing layer, including EPDM, as part of a standard green roof build-up.

Do I need the drainage board as well?
Yes, in almost all cases. Root barrier stops roots reaching the waterproofing, but a separate drainage layer is still needed to move water to the outlets and protect the substrate above — see our Green Roof Drainage & Water Reservoir Board.