Masonry facades

Arguably, a change in moisture content is a change in chemical composition, as are the effects of ice forming in the pores of brickwork. However, matters of concern are more likely to be:

• sulphate attack;
• corrosion of metals built into brickwork; and
• crystalline salt formation.

Expansion forces arising from these sources cannot be calculated in the same way that moisture and temperature movements can. They are unpredictable and will continue for as long as the circumstances that bring about the change exist. The forces can be very large and can cause significant damage. Generally, you would not design movement control joints to deal with expansion due to chemical changes; it is far more appropriate to design out the risk of these changes occurring.