Stove fire bricks, because of their continued exposure to the intense heat through direct contact with burning fuel and with their potential to be abused by over-firing, are regarded by stove manufacturers as 'consumable' parts and therefore generally receive limited coverage under the terms of the stove's warranty. Since stove fire bricks are considered 'consumable' components it is important that they are routinely inspected for signs of wear and tear.
There are basically three types of stove fire bricks – traditional refractory clay fire bricks, heat reflecting vermiculite panels and steel or cast iron fire 'cheeks'. Some stoves, like the popular Charnwood Country 4 and some boiler stoves do not actually use any fire bricks. Fire bricks only need replacing if damage to them begins to expose the stove's bodywork to flames. In severe cases of prolonged exposure this could permanently damage the stove by cracking a cast iron side panel or warping the steel bodywork.
Where clay fire bricks are cracked their lifespan can be prolonged by filling the cracked joints with fire cement – this is perfectly acceptable practice and nearly all manufacturers recommend this. Crumbling clay fire bricks, severely pitted vermiculite fire bricks or badly damaged or 'holed' cast iron fire cheeks should always be replaced.
Due to delivery costs and handling difficulties most refractory clay fire bricks are nowadays replaced with the lighter and much more cost-effective vermiculite panels without suffering any operational loss of efficiency from the stove. It's almost impossible to transport a set of clay fire bricks today without having them crack in transit no matter how well they are protected.
The cast iron fire cheeks that some manufacturers use, particularly in traditional inset stoves, where space in the smaller fire chamber is at a premium, are generally thinner than vermiculite or clay firebricks and therefore should be replaced with like-for-like where possible.
To remove fire bricks it is usually necessary to remove the baffle plate first which sometimes rests on top of the fire bricks as many stoves use this method to keep the fire bricks in position, making them much easier to remove. This will provide you with an opportunity to clean the top of the baffle plate (and flue way) as well as to check its condition. Occasionally some stoves also feature fire brick retaining brackets on each side and these should be removed as well. Even with the bracket and baffle plate removed some bricks are still difficult to dislodge and need to be carefully prised out with a screw driver or chisel, being careful not to damage them.
If you need to replace a refractory clay fire brick with a vermiculite brick then, to ensure a neat fit, it may be easier and more practical in the long run to replace all of the fire bricks with the vermiculite equivalent. Vermiculite panelling can be easily sawn and shaped so that fire bricks for even the very oldest stoves can always be safely replaced.
