HOW-TO · WATERPROOFING

How to waterproof exterior walls against rain

Driving rain soaks into exterior walls and shows as damp inside. Here is how to protect and decorate outside walls with SUMO Weatherguard.

LEVEL

Beginner

TIME

2 coats + cure

STEPS

WHO THIS IS FOR

Homeowners and applicators protecting exterior masonry walls from rain penetration.

Exterior walls take wind-driven rain that soaks through porous plaster and shows as damp patches indoors. A decorative waterproof coating both seals the surface and finishes it. SUMO Weatherguard is a high-performance acrylic waterproof decorative coating for exterior walls and masonry.

This guide covers protecting and decorating an exterior wall in one system.

BEFORE YOU START

What you’ll need

WEATHERGUARDacrylic exterior waterproof coatingExterior Wall Waterproof Coating5 kg→SEALCRETEfor crack repairAcrylic Waterproofing Liquid1 kg→

Wire brush, brush and roller

THE METHOD

Step by step

Clean and repair the wall

Remove dust, algae, chalking and flaking paint so the surface is sound and clean. Cut out and fill cracks with a repair mortar so they do not re-open.

WATCH OUTCoating over cracks and flaking paint fails fast. Repair and clean back to a sound surface first.

SEALCRETEPRODUCT USED IN THIS STEPAcrylic Waterproofing Liquid1 kg→

Let the wall dry

Make sure the wall is dry before coating — trapping moisture under a coating causes blistering.

Apply the first coat

Brush/roller a full, even first coat of SUMO Weatherguard, working it into the surface with no misses.

WEATHERGUARDPRODUCT USED IN THIS STEPExterior Wall Waterproof Coating5 kg→

Apply the second coat

Once the first coat has dried enough to over-coat, apply a second full coat for even colour and a continuous waterproof film.

PRO TIPTwo coats give both the colour and the waterproofing — one coat rarely does either well.

Cure and inspect

Let it cure, then check coverage after the next rain. Touch up any thin or missed areas.

AVOID THESE

What to avoid

!Coating a damp or dirty wall

It blisters and peels. Clean, repair and dry the wall first.

!Ignoring cracks

Cracks let rain in behind the coating. Repair them before coating.

!One thin coat

Thin film means poor colour and waterproofing. Apply two full coats.

QUESTIONS

FAQ

How do I stop rain soaking into my exterior wall?+

Clean and repair the wall, let it dry, then apply two coats of an exterior waterproof coating such as SUMO Weatherguard.

Is Weatherguard a paint or a waterproofer?+

Both — it is an acrylic waterproof decorative coating for exterior walls and masonry, so it seals and finishes in one system.

Why is the inside of my wall damp after rain?+

Rain is penetrating the porous exterior. Repair cracks and coat the outside face with a waterproof coating to stop it.

THE KIT

Products used in this guide

WEATHERGUARDSUMO PRODUCTExterior Wall Waterproof Coating5 kg→SEALCRETESUMO PRODUCTAcrylic Waterproofing Liquid1 kg→TERRACEGUARDSUMO PRODUCTReinforced Terrace Membrane20 kg→PLASTERSUMO PRODUCTReady Mix Plaster40 kg→

NOT SURE ON YOUR JOB?

Send us your substrate and tile size — our technical team will confirm the exact method.

Read the datasheet →