Today we have had a phonecall about the cast iron back firebrick in the celtic fireplace and why does it move up and down and do i have to seal it shut.
The idea is to have this little replacement brick as when the fireplace is being used for solid fuel use there is a little expansion and contraction but primarily this firebrick is where all the heat is contained and as these are proper working fireplaces the brick is designed to be replaced when it shows sign of wear and tear.
Now recently we have had one or two customers ring up saying that the replacement brick has bowed in towards the fire and it is really damaged.
This basically is though not backfilling the fireplace as the area behind the cast iron back needs to be packed tightly with vermiculite or rubble making sure that no air pockets are left.
Heats registered fitters will enusre this job is done properly and its normally DIY people we find who have not backfilled at all or done it wrong.
Its not the end of the world as the bricks are replaceable and cost £25.
So back to the original question leave the firebrick with its cast iron brackets that hold it in place and do not overtighten and make sure it moves up and down backfill the fireplace properly and all will be good for years to come.