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The Best Paint To Cover & Block Stains

Stains on walls! They can be such as nuisance, especially when you have only just decorated. It is crucial not to just paint over the stain as you will not solve the issue, which is why there are a huge range of paints that covers stains or stain blocking products on the market today. In this article we will give you all the information you need to find the best stain cover or blocker for you.

A wall that requires a stain blocker

What Causes Stains On Walls?

Firstly, let's establish what causes stains on interior walls. The vast majority of stains are caused by moisture that is leading to discolouration or damp on the wall. Water stains can be caused from a range of sources, including leaking pipes or penetrating damp caused by water ingress on an exterior wall that is soaking through to the interior wall. An alternative cause of a stain could be nicotine, which is not as common as it used to be but can be difficult to treat nonetheless.

On exterior surfaces as you may be able to tell, moisture is also the main cause. Rain water will actively attack exterior surfaces causing them to discolour & stain, especially on untreated brick walls. This is the case with both painted and bare exterior walls, as both standard acrylic paints and bare bricks absorb moisture. When this moisture is absorbed, it not only stains the wall, but leads to mildew and other green growth.

While preventing the source of the stain is always the first port of call, using a paint that covers stains or a stain blocker can provide a perfect solution to the problem to an on-going stain.

How Do You Identify The Source Of A Stain?

In order to address any stain or damp problem, you first must identify the source of the issue. There are a number of indicators that can identify where it may be coming from. Here are the most common sources and the things to look for:

  • Penetrating damp - penetrating damp is caused by water ingress on an exterior wall. It can occur at any level of the building and can be indicated by efflorescence on brickwork, blown brick faces or damp patches on exterior walls.
  • Rising damp - unlike penetrating damp, rising damp only occurs at the bottom level of the building. It is caused from ground water, which slowly works its way up an exterior wall until it soaks through to interior walls.
  • Roof leaks - ceiling stains on a top level room could be a sign of a roof leakage. Common stains occur when a chimney is not properly waterproofed, causing moisture to stain the ceiling near the chimney breast.
  • Water leaks - water leaks can occur all over the home. If you have a stain around the area or below a plumbing fixture, this could be a key indicator of a pipe leak.

While this list is not exhaustive, it does contain the most common causes of stains. Make sure you prevent any further moisture by dealing with the source of the problem. Simply painting over a stain will not solve the problem, unless the moisture has stopped.

The Best Stain Blocking Paint

When it comes to solving problems, no decorating brand does it quite like Zinsser. Their range of paints & primers contain some of the most popular problem solving products available in the UK, from AllCoat to BIN. Zinsser Ceiling Pro 5-IN-1 is their dedicated ceiling paint that acts as a sealer, primer, decorative finish & will cover hairline cracks, all in one product. It also contains a biocide that protects the dried coating against fungal degradation and has fantastic stain blocking properties.

It provides a perfect finish on ceilings every time, which is why it is increasingly popular at the moment. While it is only available in white, this should not be an issue as the vast majority of ceilings are painted white.

The Best Stain Blocking Primer

If you are painting in a mixed colour for example or want to treat an interior wall before painting, a stain blocking primer is your best bet. This is the most common solution used by homeowners & decorators, as it allows you to treat the surface before applying a paint of your choice, allowing for greater flexibility. Luckily for you there are a number of excellent options on the market, mainly from Zinsser.

Our personal recommendation would be to use Zinsser Coverstain, which is a low odour oil-based primer & stain blocker. Zinsser Coverstain can be used both on interior & exterior walls and is especially effective on nicotine and water stains. It acts as an undercoat that can be painted onto, that possesses excellent stain killing performance.

Zinsser BIN is the sister of Zinsser Coverstain, which is a shellac products that shares the same stain blocking performance of Zinsser Coverstain but with the added bonus of faster drying - 15 minutes to be exact! As Zinsser BIN has extremely good adhesion qualities it is more expensive than Zinsser Coverstain, but it completely depends on the extent of your staining as BIN is a high performance all-round primer & sealer.

The Best Exterior Stain Blocker

Both Zinsser Coverstain & Zinsser BIN can be used on exterior walls. Just like interior walls, exterior walls are prone to stains & discoloration due to moisture. If you are using a non-waterproof masonry paint, these stain blocking primers are great options.

If you are planning on re-painting your stained exterior walls, then it is important to consider preventing the moisture ingress altogether. Waterproof masonry paints such as Emperor Masonry Paint are designed to prevent this water ingress completely by creating a water repellent surface on the exterior wall, while also maintaining full breathability which allows moisture to escape the property. This allows the masonry to remain dry & thus prevents any discolouration or water stains. Not only this, but just like water, dirt is repelled from the painted exterior wall, meaning they stay looking like new for 25+ years.

If you are looking for a clear stain blocker, than this super hydrophobic technology is also available in a clear masonry cream, which does not alter the appearance of the brickwork. Masonry cream is an effective treatment for a white, chalky substance on exterior walls called 'salt efflorescence'. This is caused by the water absorbing into brickwork, which allows the salt in the brickwork to migrate out of the brick, leaving large white marks on the exterior wall. By preventing the moisture & maintaining breathability, this efflorescence is continually reduced until it disappears.

Efflorescence on brickwall
Salt efflorescence

Frequently Asked Questions

Q. Does stain block paint stop mould?

Stain blockers will allow moisture to escape, which will help prevent the regrowth of mould, although it will not solve the source of the moisture. If you want to prevent mould, you must first attend to this.

Q. How do you clean mould off a wall?

To remove mould from an interior wall, use a mix of one part bleach to four parts water. You can then wash down the wall using the cleaning solution and a cloth, scrubbing the mould off.

Q. Can you paint over mould?

Painting directly over mould is not a good idea. You must remove the mould before painting, as it will simply grow back again. First deal with the source of the water, then clean off the mould, only then can you paint or prime over the area using an stain blocker.

We hope this has answered any questions you may have had regarding the best paints to cover & block stains. Our team of experts are on hand to assist you with any questions you may have. Simply send an email to or send us a message on social media. At Painters World we have a wide range of paints 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!

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