Stains coming Through on a Painted Garden Wall

Updated May 5, 2024 | Posted Aug 30, 2019 | Professional insight, Product Advice | 0 comments

You buy good quality trade masonry paint to spruce up that garden wall. You sheet up, sand off, blow the cobwebs off your brushes and away you go. Only to notice big brown horrible looking stains coming through the paint!! This is not a good look for your garden!! Shock horror, but what did you do wrong? In this blog, I’m going to talk about how you stop stains on a painted garden wall.

 

Why do we See Stains and How do we Stop it?

 

Let’s have a look at what is causing the issue. A garden wall rarely has a damp membrane, meaning it contains a certain amount of water. That is a problem when painting for a couple of reasons; firstly, as you’ve experienced, you get nasty stains coming through your new paint. The other issue is eventually that water is going to build up behind the paint and cause it to lift. In fact, if you phone Dulux Tech Support, they’ll tell you not to paint a garden wall at all! For me, get it painted to your taste, but expect to have to re-do it every couple of years.

Let’s deal with those stains to stop them coming through! The issue happens because you’re using waterbased masonry paint. The water stain can simply bleed through. To stop water, you need oil!!

There are a couple of different techniques you can use. Presumably at this point you have already applied a coat of paint to your wall. You could simply block out the stains using oil-based undercoat, touch up with your water-based masonry paint, then apply a full coat of masonry to the whole wall. You can use other products such as Zinsser Cover Stain.

Or, and a better option, why not use oil-based masonry paint?  It’ll block the stains and will look fresh for a good couple of years. Get a good trade paint (sometimes called pliolite based masonry), and dilute it slightly with white spirit. The advantage of using an oil-based coating over the whole wall is that the water stains will not manifest somewhere else.  The paint will still fail over time, there’s no stopping it.

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Eventually the moisture underneath will build up and the paint will flake. You’ll probably get a couple of winters out of it before you need to paint your wall again.

Just try not to get too much pliolite on your skin because it can be hard work to remove.

It’s worth mentioning, if this is the first time you’re painting said garden wall, lime or mineral paint is the way to go. It won’t stain and allows water to pass through, so your finished wall will remain looking new for yonks. However, lime or mineral based masonry paint will not help if your wall is previously painted.

There is plenty of other information available on the Decorators Forum UK

 

Best Paint to Use on a Garden Wall

 

I just wanted to end by giving you my recommendation on the best paint to use. As mentioned earlier in the blog, oil-based or pliolite-based masonry paint is the way forward. There is a brand of pliolite-based masonry paint that blocks stains but remains breathable, which will help with longevity of finish. My paint of choice is the Wethertex PP77. You can buy it online at Rawlins Paints.

This blog was written by Mike Cupit, a Professional Decorator of over 20 years and owner of Decorators Forum UK.

Updated May 5, 2024 | Posted Aug 30, 2019 | 0 comments

About the Author

About the Author

Mike Cupit has been in the decorating industry since 2002 and has mostly worked as a Trade Decorator in the domestic sector (peoples’ homes). Self-proclaimed “product geek”, Mike has a passion for paint and decorating tools. Mike now spends most of his time testing paint products and tools, comparing them to similar products on the market, and blogging about the industry in general.

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