Techniques for painting masonry (paintbrush, roller, spray gun, types of paint)Depending on the weather in your area it may be necessary to repaint the outside of your house every five to six years. It will improve the look of the property as well as protect it against the elements. It should be done in dry weather.
Types of paint
The types of paint used on masonry can be solvent-based, acrylic or reinforced paint. Solvent-based epoxy has top adherence properties, is tough and has excellent chemical resistance, but is completely inflexible, can't take high heat and discolours quicker than other types. Reinforced paint consists of fine aggregate or powdered mica and is highly weatherproof - ideal for coastal regions. The advantage of latex is that it can move and breathe with brickwork, which is important to prevent mould or mildew on the inside.
Preparing the painting surface
Pre-painted walls should be washed thoroughly with detergent to remove greasy or other build-up. Divide the project in small manageable sections with the breaking points at downpipes, corners and doorframes to disguise joints. Measure the surface to be covered to determine the amount of paint needed. The area that can be covered will be indicated on the tin label. Rough surfaces will require more paint than smooth ones and two coats should be adequate, but a porous surface may require more. You can add 20 percent water to the mix in the latter case.
The majority of masonry paint is water-based and normally would contain additives that prevent mould growth. If it is a newly plastered wall, leave it for 6 weeks to properly cure and to reveal any signs of efflorescence - a white crystal-like deposit that is often found on newer masonry. This deposit should be removed first before waterproof paint is applied. It can be done with warm water and soap and scrubbing with a hard-bristled brush. Thoroughly rinse afterwards
Holes in masonry and crumbling should be fixed before you paint it. Cement filler can be used and must be sanded evenly with the surrounding areas and left to dry completely before painting. For smaller holes and cracks caulking can be used and sanded afterwards to remove protruding pieces of caulking. If a solvent-based paint is to be used the wall should be sealed with a latex primer for masonry surfaces, or masonry sealer.
Make sure you have the appropriate paint for the job, such as exterior paint for the outside and interior paint for the inside. Open the windows for good ventilation. Acrylic paint should not dry too quickly and to prevent this the surface can be dampened slightly before sealing it with acrylic masonry primer. The primer should be more or less the same colour as the paint and for that you can add some of the paint to the primer. If you do it this way you may only need one coat of paint for the job. Acrylic masonry primer will be easier to clean and softer on your lungs.
When using a paintbrush, a width of 100mm to 150mm and with coarse bristles is ideal, because smaller will take much longer and bigger can wear you out. To get an even spread of paint you can apply it with criss-cross strokes. When you paint pebbledash, a normal brush won't cope with the uneven surface. A banister brush is best suited for this and when painting in circular motion it will do a great job.
Paint rollers will do the job three times faster than a normal brush, but they can wear out quickly on masonry. You can use a medium pile roller on smooth masonry, but with rough surfaces you will need longer piles. To avoid stroke marks, constantly vary the stroke angles. When using a ladder you may have to set up a platform to put the tray on.
When you use a spray gun you will have to do a lot of preparation beforehand, such as masking surfaces that you don't want to be painted with masking tape and newspaper. The paint will have to be thinned by about ten percent. Apply the paint in parallel strokes, overlap slightly each time and keep the gun straight and about 225mm from the surface to be painted.
Stir all paint mixes regularly to keep it consistent. You may be concerned about where discarded paint goes at the end of a job when you flush it down the drain. You could paint something out of sight, such as a very obscure corner or piece of wood panel. Dilute the paint by partly dipping the brush in water and paint again. This will contribute a lot to protecting our water sources. When you scrape off old paint, make sure it is not lead-based. Older paints will most probably contain lead. Enquire from your local council on what the regulations are concerning lead paint.