To the uninitiated, mortar’s role is to bind bricks together, to seal irregular gaps between masonry and to provide a barrier to the passage of moisture. The correct designation of mortar is vitally important in providing not only strength to the wall construction but also durability against water.
Mortar is an integral part of brickwork. It accounts for, on average, approximately 17.5% of completed brickwork. It is therefore crucially important to choose the correct mortar. Ultimately, choosing the correct mortar is just as important as selecting the best brick.
The key considerations are driven by technical performance, environmental considerations and aesthetics. Mortar can either be delivered or mixed on site, depending on your wishes and needs. A good quality building sand should always be used. Sand with a high percentage of fine particles or containing clay/silt will require additional water in the mortar mix, produce a weak mortar, provide reduced durability and may result in shrinkage of the mortar.
Lime mortar is currently popular. It is aesthetically attractive, due to the larger aggregate particles and the softer colouration. This is especially true when used in conjunction with ‘premium’ bricks such as handmade bricks. The construction industry is always looking at ways to minimise the environmental impact of both initial build as well as the lifetime of buildings with sustainability at the forefront. Lime mortars require less energy to produce than cement and hence lower CO2 emissions as well as re-absorbing CO2 during setting.
Due to their higher flexibility, lime mortars significantly reduce the need for movement joints, creating a more pleasing look. They also have self-repairing properties “autogenous healing” as any cracks that appear in the mortar will re-seal when the mortar next becomes wet, typically through rainfall. Lime mortars offer good vapour permeability, which enables the building to breathe, allowing moisture movement through the building and assisting in the drying out process.
However, it is important to stress that lime mortar is not the only, nor always the best, option. It is not as quick and easy to work with as other mortars and not everyone wants a white mortar. It can be quite a strong contrast to our bricks, particularly the darker blends. Golden ‘biscuit’ browns with a grit sand or yellowy creamy browns, again with grit sand added to the mortar, help the bricks to give the brickwork a traditional character and don’t ‘clash’.
Ultimately it depends on the brick and the effect you want to have. For example, on the Lancer Square development in Kensington, for which we are supplying the bricks, the architects have gone for quite a dark mortar to complement the particular colour of bricks they have chosen and it looks fantastic.
It is important to remember that, expense wise, mortar is an even smaller percentage of the build cost than the brick, so it is worth choosing exactly what you like, rather than jeopardise the whole appearance of your building project.