Exterior walls are subjected to the elements everyday, so take your time to consider the surfaces you’re working on and follow these steps to ensure you achieve the best results.
It’s really important to check for any signs of decay or rot before painting timber. If you do find any, the likelihood is that there’s more, so take it down and replace it with new wood. For cracks and holes, use a good quality filler applied with a putty knife. Remember that putty often shrinks when setting, so always overfill with a little more than needed. For wooden structures that need movement such as a gate, use a flexible filler.
If timber is bare and has been weathered by rain or wind, it may need to be sanded down to avoid peeling and flaking.
Different metals have different properties, all of which react to paint differently. Bear in mind the type of metal you’re painting to ensure you get the best results. Metals such as aluminium, copper, brass or stainless steel cannot be painted. Some metals are also likely to rust – think wrought iron or steel – so ensure that their surfaces are cleaned and rust free before painting. For metals that are already rusty, sand them down or use a wire brush to remove the rust then apply an all-metal primer.
Stripping and sanding
To strip back paint, you’ll get the best results by using a heat gun or a chemical stripper. If you’re only working on a small area, try a wirebrush or dry scraper. For sanding, you may want to get a mechanical sander to avoid hours spent labouring with sandpaper.
Use a solution of one part household bleach solution mixed with three parts water to remove surface mould with a scouring pad. Always wear gloves and goggles, and leave the solution on the affected area for 15 minutes before washing with clean water. Repeat to fully remove the mould as it can take several attempts.
Flaking and peeling
North- and west-facing walls are most prone to flaking and peeling as these areas receive the most heat from sunlight. Flaking and peeling is usually caused on wooden surfaces by moisture being trapped beneath the paint and is more common with dark colours and those that have been applied over old paint. Try to root out and eliminate the source of the moisture – this is usually via cracks under windows and doors or through condensation in the walls
For painting these inevitably rougher surfaces, it’s important to remove all loose material with a stiff brush. If the surface remains powdery or porous, priming is recommended to improve adhesion and durability of the paintwork.