Frost can damage damp brick walls as the moisture inside freezes, causing the brick surface to crack or flake. Sealing the bricks with a silicon treatment should be avoided, as it traps moisture leading to larger chunks breaking off and can alter the bricks colour and texture.
Frost damage is worse when cement mortar is used. This is hard and doesn’t let water evaporate, forcing moisture through the bricks and increasing damage to the bricks. Traditional lime-based mortars are more absorbent and porous, allowing water to evaporate fast and move more freely.
Cement can also harm brickwork because it sticks firmly to soft, traditional bricks, while lime mortar allows for slight movement without causing damage. When stressed, cement will damage the brick before giving way itself. Bricks are less likely to fail in lime mortar walls, but if they do, repairs are easier, as bricks can often be reused, making small repairs possible without needing to rebuild entire walls.
Small scale patch repairs can usually be carried out without Listed Building Consent if they match the existing materials and detailing.
Larger repairs or structural changes may require consent and a formal application for Listed Building Consent.