I'm fitting a cast iron fireplace which needs to be kept about 7 cm off the wall to fit into the rebate in the surround. I was going to use slabform rockwool but celotex is better as it keeps it nicely in place while I fit mortar around it. It may be used as a solid fuel fireplace in the future. I presume this is perfectly safe to use as it is just another form of insulation?
Is it ok to use Celotex behind my cast iron fireplace to help fit it?
Aug 09, 2008
3 Replies
I can't really picture what you are describing, but the basic polyisocyanurate foam burns, giving off cyanide. I believe the products such as Celotex and Kingspan have fire retardents built in, but I still wouldn't put them near anything hot. Foam certainly melts, and although fire retardents may stop the foam sustaining a flame itself, it will still burn when subject to a good external heat source.
Agreed. The usual insulating material to use behind firebacks etc. is vermiculite granules - still available as 'Micafil':
formatting link
make the rigid material they call Micafil concrete you mix the granules with OPC (ordinary cement) - 1 vol of cement to 6-8 vols of vermiculite (no sand) - and add an absolute minimum of water to make a workable mix. Allow to cure and dry for a couple of weeks before lighting a fire, and build up slowly from small fires at first.
it doesn't.
It chars and doesnt give off much at all.
But you have to get it preety hot.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required