Putting Stormdry to the Test
An independent look at this brick sealer
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Stormdry is a popular brick and wall sealer that is claimed to be highly effective at protecting masonry walls from water penetration. It is a cream that can be applied to the surface of the wall and penetrates deep into the masonry to create a long-term protective barrier.
The manufacturer states that this barrier prevents water from entering the wall and causing damage such as dampness, mould, and efflorescence.
They claim that the unique formula of Stormdry masonry cream allows it to bond with the masonry on a molecular level, without altering the appearance or texture of the wall.
Furthermore, the manufacturer asserts that Stormdry masonry cream is breathable, which allows moisture to escape from the wall and prevents any trapped moisture, such as condensation, from causing further damage.
This product is marketed for use on a wide range of masonry surfaces, including brick, stone, and concrete.
Here we independently test and review Stormdry to see how it performs against the claims made by the manufacturer.
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:
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.
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:
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.
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:
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.
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
- Easy to apply.
- Repelled rainwater as advertised.
- It penetrated into the brick, much deeper than liquid products we’ve previously tested.
- It will protect cavity wall insulation, provided the wall is sound.
- We haven’t seen any evidence that it causes condensation or breathability issues.
- Suitable for brick, mortar and most types of stone.
- Long-lasting (25+ years).
- BBA certificate.
- 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.
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.
Can walls be painted after they're sealed?
We have researched this and have seen mixed answers from different manufacturers.
Smartseal, a competitor to Stormdry, stated in their documentation, that the wall can be painted with some types of paint but not others, while one of their representatives gave me a straight “no” answer when we asked if the wall could be painted.
We suggest erring on the side of caution and not painting over the treated wall.
There are breathable wall and masonry paints on sale that would be suitable.
Can brick sealers be used to floodproof a home?
All of the sealers we tested are designed to keep out rain and wind-driven rain.
Any water that is placed under significant pressure will push through the sealant and the bricks.
These brick sealers can help floodproof a home if they are part of a system, but they shouldn’t be relied on solely.
Stormdry states in their documentation that it can be used as flood protection, but the results will be far better if the mortar is replaced with an additive that prevents the mixture from shrinking during the drying process.
How long will it take before I can see rainwater beading on the surface?
We noticed after one week and after one month all of the water beaded on the surface.
Can a second coat be applied?
Cream-based brick sealers only require one coat as after the first coat has dried, the surface repels all moisture.
Can I use brick sealers on driveways and paths?
Wall brick sealers shouldn’t be used on any surfaces that receive foot or vehicle traffic.
There are dedicated products that will repel oils and fuels, and we feel these would be better suited to driveways.
Do brick sealers block 100% of the water?
No, if you seal all sides of a brick and leave it in a bucket of water for long enough, it will weigh more as it’s absorbed some of the water.
Brick sealers are water repellers rather than waterproofers, and there is a big difference between the two.
Can brick sealer creams reduce heating bills?
Wet walls cost more to heat up than dry walls, so if you have solid walls and they are subject to frequent wind-driven rain, you could make a small saving on your heating bill.
If you have a modern house with a cavity wall, the cost saving will be negligible as the cavity acts as a barrier protecting the inner wall from moisture.
Will a brick sealer protect cavity wall insulation from getting wet?
If rainwater penetrates an outer wall and soaks the cavity wall insulation material, it can lead to severe damp problems which can cost many thousands to remedy.
A brick sealer can stop the water from entering the cavity, but only if the wall is sound and doesn’t have cracks and isn’t flaking.
If you’ve previously had issues with damp cavity wall insulation, we recommend repairing the wall so there are no gaps, cracks or missing mortar. Only then should the wall be sealed with a brick sealer such as Stormdry.
Can Stormdry be applied to painted walls?
Stormdry should be applied to unpainted walls only, as the paint will stop the brick or mortar from absorbing the cream.
Meet The Author: Daniel Woodley
Daniel has over 18 years of experience in the construction, home improvement, and landscape garden industries.
He previously worked as a project manager and has experience in managing teams of tradespeople and landscape gardeners on both small and medium sized projects.
Daniel is also a keen gardener and enjoys growing unusual plants and tending to his lawn.
Why You Can Trust Us: Our Experience and Testing Methodology
We follow a detailed, rigorous process to create content that is helpful, factually correct and meets the highest standard of integrity.
Our 5-step process is:
1) We select a topic that we feel will help our readers.
2) The author creates the content based on their knowledge and experience of the subject.
3) We then ask an expert with qualifications in the relevant area to fact-check and review the content, which we update accordingly, if applicable.
4) The content is checked by the site owners and published.
5) We review the content yearly to ensure it’s still correct and relevant.
This guide was reviewed and fact-checked by Paul Farley, as he has experience in the building industry.
Explore: Paul’s profile and qualifications.
How We Selected Stormdry
We previously tested four different brick sealers and found that Stormdry was the best of the bunch, so we created this more in-depth review for our readers.
The Testing Period
We tested this brick sealer over a 28-day period, starting in 2023.
Where We Tested Stormdry
We tested Stormdry on three areas:
- A single brick wall on a 1980s house.
- An entire wall on a 1980s house.
- Loose bricks.
We also conducted internet research and looked for reviews and expert opinions on Stormdry and similar products on sale. We also read all of the literature and test results from the manufacturer.
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