Waterproofing Paint for Walls and Roofs: Liquid Rubber

A waterproofing paint for walls is a thick, flexible coating, usually an acrylic or rubber-based liquid, that stays elastic as walls and roofs move in the heat and cold. Brushed or rolled on in several coats, often with a fibre membrane bedded into the first, it seals parapets, flat roofs, gutters and cracked outside walls. It is not a cure for rising damp. This page explains the types, where they work and what liquid waterproofing costs per 20 L tin. Send one free request and suppliers near you will quote you directly, with no obligation.

Types of liquid waterproofing

Liquid rubber: a rubber or bitumen-modified coating that dries to a thick elastic skin. Good on flat concrete, gutters and around fittings; some types need a UV-stable topcoat.
Fibre-reinforced acrylic: a water-based coat with fibres mixed in, applied in two or three coats on parapets and roofs.
Acrylic with a fibre membrane: a liquid coat with a polyester membrane rolled into the wet first coat over cracks, joints and ridges, then sealed with more coats.
Waterproof exterior wall paint: an elastomeric wall coat that sheds wind-driven rain and bridges hairline cracks.

Where it works and where it does not

Liquid waterproofing suits parapet walls, the tops of boundary walls, small flat roofs, balconies, box gutters and wall cracks that let in driving rain. Large flat roofs often get a torch-on membrane instead. Either way, the roof needs falls to its drains, because standing water breaks down most coatings. Paint does not cure rising damp. A damp tide mark low on an inside wall points to a failed damp course, which needs repair, not another coat of paint. Fix leaks at the source and let the wall dry before coating.

Preparing the surface

A waterproofing coat only works if it bonds. Scrape off loose and blistered old coatings, clean off moss and dirt, and let the surface dry fully. Open up cracks and fill them with a suitable filler or sealant. Prime porous plaster or concrete as the data sheet asks. Bed fibre membrane into the first wet coat over every crack, joint and corner and around outlets, then apply the full coats at the thickness the tin states. Thin coats fail early. Do not apply when rain is due or when the surface is damp.

Waterproof paint prices

A 20 L tin of liquid waterproofing costs about R1,050 to R1,900, and a 5 L tin about R170 to R1,130, depending on the type and grade. Coverage is lower than wall paint because the coat goes on thick: check the litres per m² on the data sheet and the number of coats. Fibre membrane, primer and sealant are extra. For a complete job with labour and a written guarantee, ask waterproofing contractors to quote.

What to include in your request

What to seal: parapet, flat roof, gutter or wall
Area in m², or the length of parapet
Old coating type and condition
Liquid rubber or fibre-reinforced acrylic
Membrane, primer and sealant as well

Waterproof Paint for different clients

Homeowners: sealing parapets, a leaking flat stoep roof or cracked outside walls before winter rain
Landlords and sellers: stopping roof and parapet leaks before they stain ceilings and tenants complain
Body corporates and estates: planned resealing of parapets and flat roofs across every block in the complex
Shops, offices and restaurants: sealing flat roofs and box gutters over shops, offices and restaurants
Factories, farms and mines: coating box gutters, concrete roofs and tank stands on factories and farms
Builders and developers: liquid waterproofing on balconies, parapets and flat slabs before handover
Schools, churches and public buildings: resealing flat roofs and parapets on schools, halls, churches and clinics
Painters and contractors: liquid rubber, fibre coats and membrane rolls in bulk for waterproofing crews

Frequently asked questions

Is rubber paint good for waterproofing?

Liquid rubber works well on parapets, gutters, small flat roofs and around fittings, because it stays elastic as the surface moves. It needs a clean, dry, sound surface and the full thickness stated on the tin. Some rubber coatings do not cope with strong sun on their own and need a UV-stable topcoat, so check the data sheet.

Will waterproofing paint stop damp on an inside wall?

Usually not. Damp inside a wall comes from water rising from the ground, from a leak or from condensation. A coat of paint hides the stain for a while, then it blisters. Find the cause first: a failed damp course, a cracked parapet or sill, a blocked gutter or poor airflow. Fix that, let the wall dry, then paint.

How many coats of liquid waterproofing do I need?

Most systems call for at least two coats, often three on roofs, with fibre membrane bedded into the first coat over cracks and joints. Each coat must dry before the next. The data sheet gives the litres per m² for each coat, and that figure, more than the number of coats, decides how many 20 L tins you need.

Does WallPaint.co.za do waterproofing?

No, we waterproof nothing and sell nothing. We are a free quote service: you describe the roof or wall, the area and the product you want, and suppliers or waterproofing contractors near you quote directly. Ask each one what guarantee is given, in writing, and whether it covers the product, the labour or both.

Liquid waterproofing for walls, parapets and roofs

Types of liquid waterproofing

Where it works and where it does not

Preparing the surface

Waterproof paint prices

What to include in your request

Waterproof Paint for different clients

Frequently asked questions

Waterproof Paint by province and city

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