As the air is drawn into the firebox, it pushes the heat and flame towards the rear firebricks of your firebox. This causes an immense amount of expansion of the firewall. Then, as the fire dies out, your firebricks begin to contract. This process is repeated every time you use your fireplace.
In an unprotected fireplace, heat is absorbed into the firebox back wall which causes the firebricks to crack and the fireplace mortar that holds the firebricks together to breakdown, leading to expensive fireplace chimney repairs.Even the best built masonry chimney can be susceptible to heat damage over time. 8
80% of the heat generated by most fires gets absorbed into the rear firewall. Over time, cracks and deterioration can form. This used to mean that a firewall rebuild was needed to prevent a serious fire hazard. Now, for a fraction of the price of a rebuild, we can usually patch these cracks and install a radiant fireback which radiates heat into your home making your fireplace more efficient while at the same time protecting your home from further damage.
Another source of damage to the rear firewall is when water leaks come down from the top of the fireplace chimney. Firewalls and firebrick are very porous as they are intended to withstand the very high temperatures of combustion.