Factors to consider when painting brickwork

Brick manufacturers produce a large range of naturally attractive clay products to meet the requirements of their customers and as such the use of paint on brickwork shouldn’t really be necessary.

However, in certain circumstances, painted brickwork is required for matching purposes such as Planners maintaining an aesthetic in sympathy to the local vernacular.

Historically brickwork would have been painted to mask existing damage or disguise mismatched products used to create extensions or alterations over the years. These days buildings are often expected to be painted as soon as they are constructed which often results in problems of discolouration or staining caused by the migration of minerals and other soluble materials to the surface whilst brickwork is still undergoing its initial drying process.

There is also the added danger that any surface treatment may cause irreversible damage of the facings and therefore painting does not preclude good construction and detailing practices. In these scenarios the following factors need to be taken into account to minimise the risk of any permanent damage occurring to the brickwork.

Brick types

When choosing the type of brick for a wall that is going to be painted, the following qualities need to be considered in order to allow for effective paint adherence.

Suction rate/water absorption

A brick with a reasonable suction rate/water absorption is better for ensuring that the paint adheres to the substrate. Bricks of a similar absorption and suction rate should be used throughout to achieve an acceptable uniform appearance. Dense, low-absorbance bricks may not be suitable for applying paint to.

Selection of brick

Engineering bricks are not recommended for paintwork. Engineering bricks have a lower absorption rate which we have already established isn’t ideal for paintwork.
Commons are not for use in exposed brickwork but this includes under paint.
Some sanded or ‘stock’ type products may not allow paint to adhere to them properly.
Hearted or multi tonal products may be more likely to contain iron, salts or metallic deposits which may produce efflorescence and iron staining as the brickwork dries which will affect the paint colour. Plain products are better.
• Select products with a low active soluble salt content (S2).

Preparation of brickwork

Prior to painting, brickwork must be completely dry before any application is attempted. Ideally new walls should not be painted, but if painting a newly constructed wall is required, a drying time of at least 28 days must elapse. The brickwork must also not have been cleaned or treated with acid solutions. Even then, establish that the period has undergone good drying weather. Any loose materials, or organic growth must be removed before painting.

Please note: Painted brickwork that pre-dates the 1960’s may contain lead and great care should be taken in the preparation for re-coating. When dry sanding ALWAYS wear a mask. In all instances, contact the paint manufacturer for advice on application methods and health and safety issues.

Thermal expansion

Brickwork, similar to other materials, is constantly moving through thermal expansion and contraction. Any surface covering will need to flex with the construction to avoid cracking. This is important because once cracks appeared, moisture is able to penetrate the masonry. Once inside, the drying capability could be greatly affected dependant on the restrictive effect of the surface treatment and frost action may result. Therefore a breathable masonry paint is recommended.

Paint

The majority of masonry paints available at present carry a guarantee of up to 15 years, as long as they are applied in accordance with BS6150: 1991: Code of practice for painting buildings and the manufacturers own recommendations.

The constituents may contain resins which can expand and contract with the brickwork and avoid cracking. There are also vapour permeable systems available allowing the brickwork to ‘breathe’.

Stabilising solutions or masonry conditioners are also available which effectively ‘seal’ the surface to prevent any soluble or friable material emerging from the brick or mortar. These are not breathable and will seal any moisture present into the brickwork if it has not already dried out thoroughly. However, any sealing applications to bricks will invalidate Ibstock’s durability warranty.

Always seek advice from the paint manufacturer prior to coating any brickwork.

Mortar

Mortar can be difficult to paint because free alkali within it may attack paint products that are oil based. The mortar must also cure for at least 28 days before paint is applied and any debris must be removed before application.

Remember, painting your brickwork is permanent and can speed up deterioration of old walls.

For help and assistance with the painting of brickwork, please contact the Ibstock Brick Design & Technical Advice Helpline on 0844 800 4576 or email technical@ibstock.co.uk.