Painting exterior masonry is one way to help keep it in good condition and can prevent water invading the brickwork, stonework or render. Masonry paint comes in several different types, each of which is more or less suited to a particular application.
Cement paint is usually sold as a powder, to which water is added before it is applied. Whilst not the most weatherproof exterior paint, cement paint is cost effective and easy to apply. Before you apply cement paint, spray the surface of the masonry with water to stop the paint being absorbed into the porous surface. Shake the container well and then mix 2 parts paint powder with 1 part water. Mix this until it is a thick paste and then greadually add water until it becomes a smooth, creamy liquid. Cement paint dries quickly, so do not mix up more than you can use in about 1 hour.
If you are painting a wall which has been sealed with a stabilizing solution, it is a good idea to add a little clean sand to the mixture. This should be added at a ratio of 1 part sand to 4 parts paint powder. This may effect the colour of the paint, so only add it for the first of the recommended 2 coats.
Although similar in appearance and consistancy to standard emulsion, exterior-grade emulsion is specifically designed to be both weatherproof and to prevent mould growth. It is easy to use and covers well, but it is certainly worth applying two coats. On very porous surfaces, dilute the first coat with about 20 percent water, and then apply one or two full coats.
This is probably the most expensive type of exterior masonry paint, but it is also the most weatherproof. Reinforced emulsion is a resin based paint which is mixed with a very fine aggregate such as powdered Mica. I gives a slightly textured finish as a result. It is particularly good for costal properties or areas with high wind and rainfall. Two coats will give the best results, but you can also apply to an undercoat of the cheaper Cement Paint.
Spirit-Thinned Masonry Paint
As with reinforced emulsion, spirit-thinned paint is resin based. Thinned with white spirit, this type of paint can be used on new walls without alkali priming them first. However, it is still worth applying two coats.
Concrete Floor Paint
Paint specifically designed for floor use is generally resin-based to increase its durability. Especially good for garages and workshops, floor paint can also be used on paving and other concrete areas. Preparation is key to a good finish with floor paint. Make sure the area is completely free of oil, grease or dust and that it is completely dry. New concrete should be left to cure for up to three months before it is painted over. Paint around the edges of the area with a large brush, then use a roller on an extendable handle to cover the middle of the area.