Putting Stormdry to the Test

Written by Daniel Woodley. Reviewed by Paul Farley. Published to Products on: 13th April 2023.

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How We Tested Stormdry

We independently tested Stormdry by:

1) Applying it to half of a single loose brick to see if it repelled water compared to the untreated half of the brick.

2) Applying it to one brick in a wall to see if it changed the colour of that brick compared to the rest of the wall.

3) We then applied Stormdry to an entire north-west facing brick wall.

What’s in the Tub

Stormdry is sold in 1, 3, 5 and 20-litre tubs.

Each tub contains a cream-based product that we can best describe as like mayonnaise.

The manufacturer claims that 1 litre will cover around 5 square metres of wall, slightly less if the bricks are very absorbent.

Testing Stormdry on a Single Brick

For this test, we applied Stormdry by brush to just one half of a brick.

We then allowed the brick to dry for over a month and tested it by squirting water onto the treated and untreated sides to test the waterproofness. We then allowed water to pool on the surface for 30 minutes to see if the brick absorbed the moisture over time.

Here are the results:

The same brick one month later

We allowed water to pool on the surface of the brick for 30 minutes to see if the brick absorbed the moisture.

As you can see from the images, the brick fully absorbed the cream (took about an hour) and during our test one month later, it kept out small water droplets and a pool of water for 30 minutes.

Colour Test

We wanted to know if Stormdry altered the colour of the bricks, so for this test, we applied the cream to a single brick in a wall and allowed it to dry for one month.

Here’s what it looked like immediately after the application and one month down the line:

Stormdry after 1 month

As you can see from the images, there was a slight darkening of the brick, but it wasn’t significant and each week it was getting lighter and lighter. Obviously, different bricks will change shade differently, and some may not change at all.

Testing Stormdry on an Entire Wall

Next up, we applied Stormdry to an entire northeast facing wall using brushes of various sizes.

What we looked for:

• Coverage rate.
• Ease of application.
• Odour.

Here’s what we found during our test:

Coverage rate – On our north-facing wall (on a 1980s house), Stormdry covered 4.3 metres per litre when we applied it by brush.

Ease of application – We found Stormdry very easy to apply; it was like mayonnaise and adhered to the brush and wall very well and didn’t drip much. We first brushed off any loose dust and then applied the cream using narrow brushes around the window frames and wider brushes on the rest of the wall. We see no reason why the user couldn’t use a roller, but we chose brushes so we could dab the cream into the small indentations and crevices on the wall.

Odour – Stormdry didn’t have a strong odour at all, and after one month, we couldn’t notice any smell on the wall at all.

Here are a couple of photos of us applying the cream and the water beading on the surface of the wall one month later:

It took less than an hour to absorb into the bricks

Closeup water beading

How Does Stormdry Stack Up Against The Manufacturer’s Claims?

The manufacturer has made several claims about the performance of their product.

Here we take a look at how it performed in our test and we’ll also provide our opinion based on research and experience in the building trade:

Claim 1: It rainproofs the wall

From the tests we performed, we could see that Stormdry kept out moisture, such as water droplets and a small pool of water, as per the photos we took and published on this page. 

Claim 2: It’s easy to apply

We agree. Stormdry was very easy to apply and we found it wasn’t nearly as messy as we thought it would be. We’ve previously tested liquid-based wall sealers that dripped everywhere and in our opinion, this cream-based alternative is easier to apply.

Claim 3: Low odour

We didn’t have any issues with the smell of this product. Once it had dried, we couldn’t smell it at all.

Claim 4: It won’t change the colour of the bricks

It did alter the colour of our bricks but only slightly. We noticed that the darkened bricks became slightly lighter over the one-month test period. The manufacturer states that they should continue returning to their original colour over time, and from what we’ve seen, we believe them.

Claim 5: Stormdry will lower your energy bills

Stormdry has produced test results and literature claiming that wet walls are colder walls, and once treated with Stormdry, consumers may see a reduction in their energy usage as their walls will be warmer.

We looked into this, and the impressive test results and energy-saving figures published were based on a single brick wall and were compared to a wet wall.

It’s worth noting that:

• The vast majority of buildings in the UK have two walls and a cavity, so these figures may not apply to you.
• Most walls aren’t constantly wet, they are protected by the roof overhang, and they dry out naturally quite quickly after rainfall has stopped, so comparing the thermal efficiency of a sopping wet wall to a dry wall in a lab experiment isn’t comparable to a real-world situation.

In our opinion, you are more likely to make energy savings if:

• You have solid walls with no cavity and no internal insulation.
• The walls are regularly soaked in rainwater, e.g. your home is located in an exposed and windswept location.

Claim 6: Stormdry can protect cavity wall insulation from getting wet

Cavity wall insulation is a popular way for consumers to insulate their walls, but there is a risk rainwater could penetrate the outer wall and soak the insulation. This is more likely to affect homes in windswept locations such as the northwest of the UK. We have seen this first hand, and the damage to the property was immense and it cost tens of thousands of pounds to remove the sodden insulation and make good the damage caused by the damp.

We agree that Stormdry can be used to stop water penetrating through bricks and mortar, provided the mortar is in sound condition. If it’s failed, is flaking or has large cracks, it should first be raked out and the mortar joint repointed, only then should Stormdry be applied.

Claim 7: Stormdry offers flood protection

The manufacturer claims that Stormdry can be used as flood protection on walls but reading the small print, we believe that it works best when the mortar between the bricks is replaced with a mortar that doesn’t shrink during the drying process. As a standalone product, Stormdry may delay the water penetration but won’t stop it entirely. We feel that Stormdry is best used as protection against wind-driven rain but may offer some protection from short-term flooding if it’s used as part of a wider system.

Claim 8: It won’t reduce the breathability of the wall and condensation won’t get trapped in the wall

Any product that drastically reduces the breathability of the wall should be avoided, as moisture can become trapped in the wall and cause damp and mould. Stormdry claims their product is “breathable” but when we read the small print, we noticed that they claim it will reduce the wall’s breathability by around 10%. You may need to consider this if you live in a property that has had previous issues with condensation buildup, breathability or ventilation.

Roger at Skill Builder published a short video to his YouTube channel showing how he was able to push air through the treated brick with a pump, so we know that Stormdry is at least breathable under pressure.

Summary

Stormdry was the most expensive brick sealer we tested and we found it was easy to apply and once dried it effectively repelled rainwater.

Based on our experience in the building trade, the test results and the literature published by the manufacturer, we feel that Stormdry will be most beneficial in these situations:

• To protect cavity wall insulation from getting wet.
• To protect walls in exposed and windswept locations from rainwater penetration.
• On solid walls that are cold and/or frequently wet.

Pros and Cons

Cons

• Expensive.
• Won’t save much money off heating bills for most consumers, with the eye-catching marketing claims only relevant to those with solid, wet walls rather than typical twin walls with a cavity.
• Despite being marketed as a flood protection product, the small print reveals that it works best as part of a wider system.

Alternatives

As part of our research into brick sealers, we also tested three competing products (read the in-depth results here).

Climashield (sold on Amazon) – very similar in performance, was 22-36% cheaper than Stormdry (depending on tub size) but didn’t come with BBA or Energy Savings Trust approval.

Everbuild Brick Sealer (sold on Amazon) – a cheap, liquid-based sealer that we found was messy to apply and only penetrated into the bricks by a few millimetres. We only recommend this for low-value walls (garden walls, sheds, garages etc).

Emporer Masonry Creme (sold direct) – very similar to Stormdry in price and performance. Has Energy Savings Trust approval but not BBA approved.

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