How to Prep Exterior Brick and Rendered Walls for Painting

Tags: Exterior Painting


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Exterior walls face pollution, graffiti, damaging UV light, rain and fluctuating temperatures. As with all other painting and decorating jobs, prep is the most vital part of the process.

With over 20 years of experience as a painter & decorator, painting exterior walls is a regular workout! Without good preparation, your exterior painting will have poor adhesion and longevity.

Here is my no-nonsense guide for achieving the most beautiful and long lasting results when painting exterior brick and rendered walls

Remove the Old Paint

Any loose and flaking paint needs to be removed. Something best done using a good quality scraper or wire brush. Laying dust sheets around the work area will contain everything for quick disposal.

Repair

Now is the time to fix and damage.

Minor cracks and be repaired with a good quality exterior grade acrylic caulk. Hairline cracks will need to be carved out slightly with the edge of an old scraper or screwdriver so the filler penetrates deeply, rather than sitting on top which can cause your crack to reappear further down the line.

Larger holes should be filled using a render mix or good-quality masonry filler. Anything more serious will be best dealt with by a professional painter and decorator or competent handyman.

Clean

You don't need to go over the top with cleaning. But, if your wall is very dirty and you don't clean it, you may be left with an adhesion issue and poor durability.

A high-pressure sprayer can, be used to clean the walls and remove any loose material. Set the pressure level to 1500 or 2000 pounds per square inch. If you go beyond that, it may damage the mortar.

If a pressure washer is isn't available, or access is an issue, a good stiff brush and soapy water can be used.

If the surface is particularly grimy trisodium phosphate mixture can be used. But be careful when using TSP, as it can be dangerous to the skin and eyes. Wear safety goggles, gloves and a disposable mask!

If you have green algae or moss on your wall, you need multi-surface fungicidal wash to kill it. This prevents the algae from growing back after you've painted.

Chalky or unstable masonry on your wall should be primed using a good quality stabilising solution. The one I use is Zinsser Peel Stop, which is water-based, can be recoated after a couple of hours, and creates the perfect base for painting.

Final Task

Sit back, bask in the glow of a job well done, and let the surface dry ready for painting.

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