How to Waterproof Bricks to Prevent Water Ingress and Damp

This page is part of our new blog, do check out our other entries here.

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

People are sometimes surprised to discover that bricks are porous and will soak up water as quick as a sheet of paper.

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 in 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 more likely to transfer the moisture to the inner wall or develop mould/damp patches.

Dry bricks on wall

The Best Solution

You’re probably thinking that the first 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:

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.

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.

The best course of action would be to repair the damp proof course so water cannot rise up from the ground. The “DPC” is usually a plastic barrier that stops moisture from rising, it’s located about 200mm above the ground outside. It can break, split or crumble and may need to be repaired or replaced.

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 by 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 in felts and timbers, a leak near the top of the roof could 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 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.

When to Use a Brick Waterproofer or Sealer

That are occasions when you may need to waterproof the bricks from the outside by applying a product.

The most common places homeowners and professional use brick waterproofers are on exposed chimneys that are getting saturated with rain and 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 chimneys that are very tall.

Walls on houses located in exposed locations, such as on top of a hill, 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.

Brick Waterproofer or Sealer – What’s the Difference?

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.

That’s because water molecules are larger than air molecules, so they can be filtered out while air passes through.

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

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

Conclusion

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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