Vermiculite to fill in the back of a fireback ?

yes

I think so.

you could. some people put some corrugated cardboard behind the fireback with a view to it burning away and leaving enough expansion gap to prevent the fireback cracking (hmmm, right) then backfill with rubble.

I filled the void behind my fireback with plain vermiculite scrounged from discarded packing material at partners place of work. I made a slurry of cement and vermiculite /only/ for the flaunching/sloped back thingy. when used and it's covered in soot it looks ok, hasn't cracked, very inexpensive.

RT

My fireback cracked anyway, even though it was just propped against the back of the inglenook.

the one I tried to fit before this one cracked as I was putting it in :-(

this one's been in for 2 winters and, touch wood, it's a goodun

RT

B&Q used to sell a high-volume ready mixed concrete mix that used vermiculite instead of the more usual mixed aggregate. Can't find it on the website (no surprise there then), but it was only a couple of year back when I bought a bag of the stuff.

Cheers Clive

Don't add sand. Just use a 1:6 (by volume!) mix of OP cement and vermiculite with an absolute minimum of water - just enough to get a workable grey gooey mass. Well that's what I did when I put my Baxi Burnall in a few years ago and it's been fine. I didn't use any cardboard - the weak vermiculite mix will allow a bit of movement. The cardboard backing is advised if you use the option of a more solid sand, cement and rubble infill.

I bought a sack of it from Travis Perkins. Their computer said they had 3 sacks, but it took half the staff searching the yard for about

I used it as a layer of insulation under the sand and cement base for a fireplace (a sheet of expanded polystyrene seemed like a distincly bad idea;-)

Vermiculite is commonly used to insulate chimney flue liners. Try your local chimney company.

Sold as Micafil

I have found Vermiculite,

Then a web serch found various sites selling 100L bags about 17.00 + Delivery (Mostly used for growing things indoors under lights without the aid of soil. Some of the sites offered '100% Confidential service'), Also a discusion on the magicmushroomforum.

Then a phone call to a local Chimney company who gave me a name of a local company that do a 100L bag for 8.80 + Vat, and they have a trade counter and I can collect.

Result !!

Graeme.

According to my brickie, the old way, is a very week sand/cement dry mix. He better be right, I just did my whole chinmey this way.

Rick