The Truth About Wall Sealing Paint

What Is Wall Sealing Paint?

The first step is to establish what we mean when we are referring to a 'wall sealing paint'. The reality is, this can refer to many things, but most commonly means a waterproofing masonry paint that protects exterior walls. Many homeowners are under the impression that their exterior walls, be it brick, stone or render, are waterproof. However, this is not the reality. These mineral surfaces are actually porous, meaning they can absorb water. The more porous the material, the more water will can absorb.

When this moisture absorbs into the exterior walls of a property, it can lead to a number of problems, which include:

• Damage - when moisture that has absorbed into the wall undergoes a freeze-thaw-cycle when temperatures drop, it expands, causing render, brick or stone to crack under the movement. These cracks in turn allow more water to enter the wall, which simply creates more movement and more damage each time. Consistent exposure to water can also cause bricks & mortar to crumble over time, leading to aesthetic and structural problems with exterior walls.

• Damp - penetrating damp is caused when water absorbs into the external wall of a house and through to the internal walls, causing crumbling plaster, damp & black mould.

• Discolouration - moisture will provide the ideal conditions for moss, lichens & other organic growth to develop. Eventually the exterior wall will become dirty, discoloured and unattractive from the growth, leading to regular cleaning & maintenance.

• Heat loss - damp content of 5% can lower the insulation properties of a surface by 50%. Wet walls mean cold walls, as moisture allows heat to be lost through the external wall of a property much quicker than when it is dry.

All of these side effects of water entering through the external wall of a house can only be resolved by preventing the porous exterior wall from absorbing moisture. Unfortunately, standard masonry paints do not prevent this absorption as they are most often acrylic-based masonry paint. Acrylic masonry paints can actually absorb some moisture, which is why they are often referred to as 'weatherproof' or 'weather resistant', rather than waterproof. For a masonry paint to be waterproof, it must be water repellent.

The Importance of Breathability

When using a waterproofing treatment of any kind, the most important aspect is breathability. Breathability refers to the ability for water vapour to naturally breathe through the surface without being trapped. If a surface cannot naturally breathe, any moisture present within the material will become trapped. In the case of exterior walls, this leads to very high-moisture levels within the wall that over time will lead to the same damp & damp that is caused by water absorbing into the wall.

Eventually, once the moisture levels reach the maximum level possible, the pressure that is caused will lead to the coating of the waterproof treatment being burst, leaving the surface untreated and in a worse state than it when it was originally waterproofed.

A coating is considered breathable if it has an SD value of below 0.5. If you cannot find the SD value of a product, the chances are that it isn't breathable.

The term 'sealer' is often used when describing waterproofing treatments, however the reality is that these products often have little to no breathability. They 'seal' the pores of exterior walls, preventing water from entering the material but also preventing water vapour from naturally breathing out. This is why sealers have gained a poor reputation in the UK over the past decade.

It is also important to mention that acrylic masonry paints generally have low breathability, which is why they often fail after a matter of years when the water they can absorb becomes trapped underneath the paint film.

What Waterproofing Treatments Should You Use?

If you are looking to waterproof an exterior walled surface, such as brick, stone, render or concrete, you must use a highly breathable waterproofing treatment that creates a water repellent surface on the wall.

There are two forms of highly breathable waterproofing products on the market in the UK. These come in the form of waterproof masonry paint & masonry cream. Here at Painters World we stock Emperor Paint products, which are the most advanced exterior waterproofing products available on the UK with their super hydrophobic nano-technology.

This allows them to line the pores of exterior walled surfaces, without sealing them, preventing water from being absorbed while allowing water vapour to still breathe through the wall. This is achieved as the lined pores are too small from water to pass through, but large enough that water vapour is not trapped.

Both Emperor Masonry Paint & Emperor Masonry Creme have been independently tested & shown to prevent 96% of water absorption, while also being highly breathable, with SD values of 0.03 and 0.01 respectively. Emperor Masonry Paint & Emperor Masonry Creme were also put through a 25 year accelerated weathering which found that after 25 years of harsh weathering, both treatments showed no change in appearance or performance. For this reason, Emperor Paint offer a lifetime guarantee on all products.

By keeping exterior walls dry, in the testing, the treatments were also found to keep a treated wall 6°C warmer on average compared to a wall left untreated.

You may be wondering what is the difference between a masonry paint & a masonry cream? Well, while a masonry paint creates a coloured finish to exterior walls, a masonry cream absorbs into bare brickwork, creating a completely invisible waterproof barrier on exterior walls. This means that even if you want to maintain the natural beauty of you bare brickwork & masonry, you can still provide it with waterproof protection.

Emperor Masonry Paint on the other hand is available in 12 popular exterior colours, including neutral shades such as white, off-white, light grey & beige, plus a number of beautiful pastel shades such as rose pink & crystal blue.

Read more about Emperor Paint.

How To Waterproof Walls

The application process of applying masonry paint and masonry cream is different, however there are a number of similarities. The main difference is that Emperor Masonry Creme is a one-coat, gel-like substance that is simply applied to the bare masonry wall like a suncream and left to soak in, while Emperor Masonry Paint is a two-coat paint that is applied like any other paint.

What You Will Need:

• Masonry paint or masonry cream
• Primer (if required)
• Filler
• Filling knife
• Paint brush
• Long-pile roller
• Masking tape

Repairs

Before applying anything to a surface, you must ensure it is sound. If you have any cracks or holes in the wall, apply an exterior filler such as Toupret Fill-Flex Exterior Flexible Filler using a filling knife and leave to dry, before sanding back to a smooth edge. If you are using masonry paint are have any areas of paint that are peeling, remove these using a scraper until no more paint is easily removed.

Clean the surface

Any dirt on the surface of exterior walls will prevent waterproofing coatings from adhering to the wall properly, running the risk of it failing. Clean the exterior wall down using a hose pipe or a dust brush, ensuring you have removed any large bits of dirt. If the wall has any sign of organic growth, this needs to be killed before you apply anything. You can do this using a fungicidal cleaner such as Emperor Masonry Cleaner.

Masking

Protecting surfaces around you is crucial if you want to achieve neat and tidy results. Apply masking tape to any edges, cover any drainpipes with newspaper, put a dust sheet down on the floor and apply window film to any windows you want to protect.

Priming

Applying a primer is required if you are painting a bare surface that has not been previously painted. It is not required if you are using Emperor Masonry Creme however, as this is not a paint. It is also important that you apply the correct primer. Emperor Exterior Primer is specifically designed to be used with Emperor Masonry Paint, for example. A primer is a thin liquid that can be applied easily using a brush or roller in just one coat. Leave to completely dry before you move on to painting.

Application

You can apply exterior paints and coatings by brush, roller or spray application, but most people will use a combination of brush and roller. It is important that you do not apply anything at temperatures below 5°C, as this will impact its ability to dry properly.

Start by applying the product you are using to the edges of the surface, starting at the top. Once you have done this, you can use a long-pile roller to apply it to the rest of the surface. A long-pile roller has long fibres, allowing it to paint rough exterior surfaces quickly and effectively. If you are applying masonry cream, you can leave this to cure into the wall over the course of a couple of hours. If applying masonry paint, after an 8 hour period, you can then apply your second coat.

The full water repellent properties of the products will not be visible straight away, as they must cure first. Emperor Masonry Creme has a curing time of 2-3 hours, while Emperor Masony Paint cures over the course of a couple of weeks. During this period they will still be waterproof and will not uptake moisture.

Frequently Asked Questions

Q. How do you seal interior walls?

It would depend what you mean by 'sealing' interior walls. If you are looking to prepare a chalky wall ready to paint, you will need to prime this using a primer such as Zinsser Bullseye 1-2-3. If you are looking to give interior walls added protection against moisture, an anti-condensation paint such as Suretherm Anti Condensation Paint will stop mould from gathering on these internal walls by preventing condensation from forming.

Q. Can you seal masonry before painting?

A common misconception when it comes to protecting masonry surfaces is that you can seal the masonry before painting it. This in any case should not be done. If you want waterproofing protection but then to paint the surface, you must you a waterproof masonry paint. You cannot apply masonry cream or a masonry sealer underneath a masonry paint as it will simply repel this paint as it would with rainfall. If your masonry surfaces are chalky and in need of a treating before a paint can be applied, this can be done using a primer, otherwise known as a stabilising solution. The difference between a stabilising solution and a primer is that a primer will act as a stabilising solution, but a stabilising solution will not act as a primer. For that reason, if you need to seal off any masonry surface to allow you to paint it, simply apply a compatible primer.

Q. Can you seal masonry after painting?

If you attempt to apply a sealer to a previously painted masonry wall, it will not be able to adhere to the surface. This is because 'sealing' products or waterproofing products such as masonry cream must be applied to bare, unpainted surfaces as they absorb into the masonry. Any paint film will simply prevent the treatment from working. The only way to waterproof a painted surface is to remove the paint or apply a waterproofing masonry paint on top.

We hope this has answered any questions you may have had regarding wall sealing paint. If you would like any more help & advice, our team of experts are on hand. Why not send an email to the team at hello@paintersworld.co.uk or message us on social media? At Painters World we have a wide range of paints & decorating supplies available, so no matter the job, we've got the right tools for you. Plus, get FREE next working day delivery on all orders over £50.