How to Waterproof Bricks: The Complete Guide

Our guide here is all about brick waterproofing, the do’s and don’ts and also some products we’ve used in the past and can recommend.

Personally, I’m not a huge fan of brick sealers, I’ve seen DIYers and professionals use them instead of solving the underlying issue, thus masking the problem rather than fixing it.

People are sometimes surprised to discover that bricks are porous and will soak up water as quick as a sheet of paper, this is in fact, perfectly normal and most house bricks do this.

The average house brick wall is designed to soak in moisture and then dry out as soon as the rain has stopped. This is why most modern homes have two walls separated by a cavity, this keeps the moisture off the inner wall so your plaster stays dry.

Unfortunately, house bricks aren’t supposed to be saturated with water permanently. If they are, there’s a good chance they will crack or spall in the winter when the temperature drops below freezing and the moisture in the bricks expands.

A house wall that is subject to a constant or regular soaking is also more likely to transfer the moisture to the inner wall or develop mould/damp patches.

Dry bricks on wall

The Best Solution

If you have an issue with a wet wall, you might be thinking that the best course of action is to seal the bricks.

You would be wrong.

The first thing you should look at is why the bricks are getting wet in the first place and do your best to remedy this.

Here are three examples that I’ve seen, they are very common:

1) Rising Damp

Rising damp is where moisture rises up from the ground and appears on the lower parts of walls and on the floor, often in the corners of a room.

Sealing the outside of the wall is not the best option as the moisture will still rise up from the ground.

In fact, sealing the outer wall could make things worse as the wall needs to breathe and despite what most manufacturers state, all of their products reduce the breathability of the bricks.

The best course of action would be to install a damp proof course so water cannot rise up from the ground.

Most modern homes have a DPC and they usually last the life of the house.

The “DPC” is usually a piece of plastic, slate or other waterproof material that stops moisture from rising, it should be located at least 150mm above the ground outside.

For rising damp and DPC issues, we recommend our guide: 7 Things You Must First Check Before Paying For a Rising Damp Treatment.

2) Damp External Walls From Leaking Roofs/Gutters

If your house is suffering from isolated patches of damp on the outer walls, you should first look at the roof and gutters.

Water can come into contact with a wall via drips from gutters or roof leaks, it can also drip into the wall cavity and come into contact with the outer wall this way.

Because roofs are covered with felts and timbers, a leak near the top of the roof could also cause water to enter the house several metres further down the roof, so check the entire roof.

Rather than applying a waterproof sealer to any damp brickwork, it would be better to find the cause of the water ingress and solve the issue at the source.

This could be something simple as replacing a broken tile, unblocking gutters or something more costly such as replacing a felted flat roof.

3) Chimneys

Chimneys are prone to leaking and I’ve personally met dozens of homeowners who’ve experienced long-term and difficult to cure chimney leaks.

Rather than reaching for the waterproof sealer, you should first try to diagnose why the chimney is leaking. The chances are that water won’t be coming in directly through the bricks.

The most common causes are:

  • Leadwork that has split, cracked or pulled out of the brickwork.
  • The chimney needs repointing.
  • The chimney flaunching is cracked or missing.
  • There’s no overhang at the top of the chimney.
  • There are tiles near the chimney that are cracked, broken or chipped.

A brickwork waterproofer won’t cure any of the above issues, in fact, it could make the issue worse as sealing wet bricks just locks in the moisture.

It can be difficult to cure leaks and dampness from around chimneys as there are so many entry points for the water. Also, the lead flashing may hide problems and a thorough inspection if often needed.

When Should I Use a Brick Waterproofer or Sealer?

There are occasions when you may need to waterproof the bricks from the outside by applying a product; for example, on chimneys and on exposed walls that receive an unusually high amount of rainfall. If you live in an exposed location that is lashed with rainfall, brick waterproofers can help keep the moisture out.

The most common places homeowners and professional use brick waterproofers are on exposed chimneys that are getting saturated with rain and where the moisture is transferring from brick to brick and eventually enters the loft where it causes issues.

If the chimney is in good condition and still has damp issues, a waterproofer can be used to prevent water from getting into the bricks.

Not every chimney suffers from these issues, the ones that do are usually located in exposed locations, typically west facing exposed locations and also chimneys that are very tall.

Walls on houses located in exposed locations, such as on top of a hill or in the west of the UK, often get lashed by rain which, in extreme circumstances could cause issues.

Assuming the mortar pointing is in good condition or has already been repaired, a brick waterproofer could help.

 What’s the Difference Between a Brick Waterproofer and a Sealer?

brick waterproofer

Historically, a sealer was a product that completely sealed the brick from moisture and air.

A waterproofer is a product that keeps the water out but allows the brickwork to breathe.

Unfortunately, the terms are often interchanged and products that are sealers are occasionally advertised as waterproofers and vice versa.

Do bear in mind that water molecules are larger than air molecules, so they can be filtered out while air passes through.

In a nutshell – you should use a waterproofer that allows the brickwork to breathe.

How Often Should a Brick Waterproofer be Applied?

A good quality waterproofer should last in excess of 15 years before you’ll need to apply another coat But this assumes that the surface is sound.

Will a Brick Waterproofer Change the Colour of the Bricks?

Good quality waterproofers are 100% translucent and once allowed to dry, they won’t change the colour of the surface they’re applied to.


Bricks may become damp, wet or mouldy for a variety of reasons and it’s best to locate and remedy the cause before applying a brick waterproofer.

These products do work at repelling water from the surface but they don’t prevent rising damp or leaks from roof/chimney issues.

The best waterproofers are those that allow the wall to breathe, this is recommended for most walls and is essential for single walls without a cavity.

Products We Recommend

Stormdry is a cream-based waterproofer that is very easy to apply, either by roller or brush.

Once dry, it keeps water out of the bricks while allowing the wall to breathe.

It’s used by professionals but is also on sale to the general public and comes with a 25-year guarantee.

Stormdry is also certified by the BBA (Certificate Number: 15/5198).

There are dozens of customer reviews on Amazon and the manufacturer has also answered over 30 questions so far.

View Stormdry on Amazon
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