Liquid waterproofing membrane — brush-on sealing for bathrooms, balconies, terraces & roofs
A liquid waterproofing membrane is a brush-on seal: applied as a liquid, it dries to a seamless, elastic film with no joints or overlaps. Ordinary DIY-store liquid membranes are made for bathrooms under tiles — our membrane based on liquid rubber also seals balconies, terraces, flat roofs, plinths and basement walls, is UV-stable and lasts outdoors.
What is a liquid waterproofing membrane?
The term describes a single-component, water-based sealing compound that is applied with a roller or brush and dries into a closed, stretchable membrane — hence "membrane" or "liquid film". Unlike bitumen felt or EPDM sheet there are no seams, no torch and no adhesive. The film follows the substrate into every corner, around every pipe and every drain.
Our membrane is an acrylic-latex coating with over 300 % elongation: waterproof (class W3), breathable (V2 per EN 1062-1), UV-tested per ISO 16474-2 and usable from −20 °C to +50 °C. It is also known as liquid rubber, liquid plastic or rubber paint.
Indoors: bathroom, shower, utility room
In the bathroom the liquid membrane is used as a bonded waterproofing layer under tiles: splash zones at the shower and bath, floors, wall junctions. Two coats with sealing tape in the corners and collars around pipe penetrations — then the tiles are bonded directly onto the dried membrane. Without tiles the coating works as a washable wall paint for wet rooms: wet-scrub class 1 per EN 13300, mould-inhibiting, low-odour.
Outdoors: balcony, terrace, flat roof
This is where our membrane parts company with indoor-only products. DIY-store bathroom membranes are not UV-stable and go brittle outdoors after one season. The liquid rubber base, by contrast, is designed for permanent weathering:
- Balcony and terrace — directly on intact tiles, screed or concrete; as a bonded membrane under new tiles per ETAG 022
- Flat roof and garage roof — refurbishing old bitumen felt without strip-out, cracks are bridged
- Plinth and basement wall — protection against splash water and ground moisture, salt-tolerant
- Metal, concrete, wood — one product for all substrates, usually without primer
Application in three steps
- Prepare the substrate. Clean, dry, grease-free. Remove loose parts, fill cracks over 3 mm, prime absorbent substrates with a penetrating primer.
- First coat + details. Apply thinned with up to 5 % water; embed reinforcing fleece (60 g/m²) in corners, at junctions and around drains. Coverage 100–200 g/m².
- Second coat. After 4 hours, undiluted and crosswise to the first. Rain-resistant after 6 hours, tile after 24 hours, fully loadable after 28 days.
Consumption and cost
For two coats allow 0.3 kg/m²: a bathroom with 8 m² of waterproofing area needs around 2.5 kg (one 3.5 kg tub), a 10 m² balcony about 3.5 kg, a 20 m² garage roof one 6 kg tub. Material costs come to roughly €4–5 per m² — a fraction of new bitumen or EPDM waterproofing.
Liquid membrane vs. bitumen and EPDM
| Criterion | Liquid membrane (liquid rubber) | Bitumen felt | EPDM sheet |
|---|---|---|---|
| Application | Cold, roller/brush | Torch | Adhesive, contractor |
| Seams | None | Weak points | Bonded joints |
| Details (corners, pipes) | Easy | Laborious | Preformed pieces needed |
| Repair | Paint over | Re-torch | Patch |
| Colour | 14 RAL shades | Black | Black, grey |
FAQ
Is a liquid membrane the same as liquid plastic?
In everyday speech, yes: both terms describe liquid-applied waterproofing. "Liquid membrane" is used more for bathrooms, "liquid plastic" for roofs and balconies. Our product covers both.
Can I bond tiles directly onto the membrane?
Yes, once the second coat has dried completely (24 hours), with flexible tile adhesive — as a bonded membrane per ETAG 022.
Does the membrane hold on old tiles?
Yes, if the tiles are firmly bonded: clean, degrease, key smooth glazes with 80–120 grit. Re-lay loose tiles first.
How long does the waterproofing last?
Many years when applied correctly; on weathered surfaces a refresh coat every 5–7 years without sanding.
Ready to start? Choose your colour and tub size.
Go to the shop → · Application overview · Balcony waterproofing · Flat roof waterproofing
Related terms: Our product is sold in DIY stores and the trade under several names — liquid rubber, liquid rubber paint, liquid membrane, rubber paint, rubberised paint, flexible coating, elastic exterior paint or polymer coating. They all mean the same product: a waterproof, highly elastic coating based on acrylic latex.