Liquid Rubber Waterproof Coating | One Coat Roof Leak Repair & Waterproof Sealant, Black 5L

Black liquid rubber roof coating for leaks and flat roof repairs

If your flat roof, garage roof or gutter is leaking but still structurally sound, you may not need to replace it. This ready-to-use black liquid rubber seals it in one generous coat, applied by brush or roller with nothing to mix. It suits homeowners, roofers, landlords and facilities teams looking after sheds, garages, extensions and workshop roofs. Each 5 litre tin covers about 5m², so measure your roof first and use the coverage guide below.

Liquid Rubber Waterproof Coating is a high-performance waterproofing solution designed to stop leaks and protect surfaces from water ingress, corrosion, and weather damage. Its easy-to-apply liquid formula creates a seamless, flexible membrane that bonds firmly to a wide variety of surfaces, making it ideal for both emergency roof repairs and long-term maintenance.

Perfect for DIY users and professionals alike, this durable coating forms a highly elastic waterproof barrier that expands and contracts with the surface, helping to prevent future cracking and leaks. Suitable for both horizontal and vertical applications, it offers a cost-effective alternative to expensive roof replacements.

Key Features

• Instant waterproof protection
• One-coat application
• No primer required on most surfaces
• Flexible and highly elastic finish
• Excellent adhesion to multiple substrates
• Long-lasting leak protection
• Seamless waterproof membrane
• Suitable for horizontal and vertical surfaces
• Easy roller or brush application
• Ideal for DIY and professional use

Reliable Waterproof Roof Repair

Designed to tackle leaks quickly and effectively, Liquid Rubber Waterproof Coating seals cracks, joints, gaps and small holes to create a durable waterproof barrier. The liquid consistency allows the coating to flow into difficult areas, providing complete coverage without seams or weak points.

Its flexible formulation withstands normal building movement caused by expansion, contraction and vibration, ensuring long-lasting performance even in demanding outdoor conditions.

Suitable Applications

Ideal for waterproofing and repairing:

• Flat roofs
• Gutters
• Flashings
• Roof joints
• Skylight surrounds
• Chimney details
• Garden sheds
• Mobile homes
• Caravans
• Metal surfaces
• Timber surfaces
• Concrete surfaces
• Masonry

Please Note: This coating is designed for waterproofing applications and is not recommended for areas subjected to frequent or heavy foot traffic.

It can be used on suitable flat or pitched roofs, including garages, extensions and garden buildings. It is for outdoor use, and it is not intended for balconies or walkways.

Benefits

• Stops active leaks quickly
• Forms a seamless waterproof membrane
• Protects against rain and moisture penetration
• Highly flexible after curing
• Excellent weather resistance
• Suitable for preventative maintenance and repairs
• Cost-effective alternative to roof replacement
• Easy application with minimal preparation

Specifications

Download the product data sheet (PDF)

Coverage Guide

Approximate coverage per coat:

Coverage rates may vary depending on the porosity and condition of the substrate.

How many tins do you need?

Multiply the length of the roof by its width to get the area in m². Allow at least 1 litre per m², plus extra for rough or porous surfaces and for reinforced joints and details.

Choosing between a tin and a kit

This single tin is the right choice for a small roof, a shed, or repairs to gutters, flashings and joints. For a bigger job, our 20m² roof repair kit and 40m² roofing kit are usually the better buy. Each costs less than buying the same number of tins separately and also includes 50m of geotextile reinforcement tape, a roller frame and sleeves, brushes, a scuttle, a mixing paddle and gloves.

Reinforce cracks, joints and details

Cracks under 4mm can be filled with uncured coating. Bridge larger cracks, splits, seams and joints with geotextile tape 10–15cm wide, along with vulnerable details such as upstands, corners, skylight bases, pipes and rainwater outlets. Embed the tape in wet coating, press it flat with no wrinkles or trapped air, then coat over it until fully covered. These details need coating beneath and over the tape, while the rest of the roof stays a one-coat job.

Surface Preparation

For best results:

• Ensure the surface is clean, dry and structurally sound.
• Remove dust, dirt, grease, moss, loose coatings and other contaminants.
• Repair damaged areas before application.
• Apply only to completely dry surfaces.
• Highly porous substrates may require a suitable primer following an adhesion test.
• Remove any rust from metal, and do not apply to freshly laid bitumen or to new or wet concrete under 21 days old.

Application

Apply evenly using a brush or roller to achieve a continuous waterproof membrane. Ensure all joints, cracks and repair areas are fully coated. Allow the coating to cure fully before exposing it to standing water or adverse weather.

1. Stir: stir thoroughly until uniform, and do not thin.
2. Coat: apply at a minimum of 1 litre per m² like a coat of paint, cross-rolling for an even finish with no missed areas or pinholes.
3. Keep to one layer: apply a single layer across the main roof, because extra thickness extends the cure time.
4. Clean up: clean tools with white spirit before the coating cures, then reseal any leftover coating for later use.

This is a solvent-based product, so wear gloves and safety goggles and read the safety data sheet before use. Do not let excess coating enter drains.

Weather and drying times

The roof must be dry during application, ideally with air and surface temperatures of 5–30°C. Do not apply to damp, frozen or waterlogged surfaces, and allow longer for drying below 20°C. At 20°C, it is touch dry in 1 hour and hard dry in 8–12 hours. Do not wash it, expose it to chemicals or let water sit on it for at least 48 hours. Full cure takes approximately 6–7 days.

Suitable Substrates

• Concrete
• Cement
• Brickwork
• Metal
• Timber
• Roofing felt
• Fibre cement
• Existing sound waterproof coatings
• Most common roofing materials
• Weathered asphalt and bituminous roofing
• GRP and fibreglass

Frequently asked questions

How long does it last?

It is designed to provide 5+ years of waterproof protection on suitable, correctly prepared roofs. The actual service life depends on the condition of the roof, its exposure, and how well it is prepared and coated.

What if it rains straight after I apply it?

Light rainfall immediately after correct application should not harm the coating, so you do not need a long dry spell afterwards. The roof must be dry while you apply it, and water should not sit on the surface for at least 48 hours.

Will it fix standing water on my roof?

No. The roof still needs adequate falls and drainage, because the coating cannot correct drainage problems. Give areas where water collects extra attention during preparation, and reinforce any vulnerable details there.

Can I apply it over an existing roof coating?

It may be suitable if the existing coating is sound and securely bonded. If you do not know what the coating is, carry out a small adhesion test before you coat the whole roof.

Can I use a normal paint roller?

Use a brush or a solvent-resistant roller, because this is a solvent-based coating. Standard sleeves may not stand up to it, and tools need cleaning with white spirit rather than water.

Ordering and delivery

Orders are sent by Express Delivery, with same-day dispatch before 2pm, Monday to Friday. For larger roofs, trade orders or a safety data sheet, call 01744 520110 or email sales@industrialsuppliesco.co.uk and we will help you work out what you need.