Fireplace backfill

[jack8]

Hope I've got this in the right section and the question isn't too daft.
Previous owner left just an oblong hole as a fireplace in the chimney breast, suppose they had removed the original fireplace. I have bought one of the all in one castiron victorian fireplaces to insert. I have built bricks inside upto about the upper opening level of the fireplace opening vent. Have bought micafil/vermiculite stuff to backfill into remaining openings.

Question is, is this poured in as it is? or mixed with water/mortar and then poured in? I guess then I have to make a mortar sloping shelf on top of this backfill to prevent soot falling behind.

What is the best way to complete the backfill?

Thanks

 

[nickjb]

Not saying I did it right but here's what i did...

Filled behind the fire place with a weak mix of sand, lime, cement, and quite a lot of vermiculite. Sat a few half bricks on top chopped at an angle to roughly form a sloping shelf. Then a bit more sand, lime, and cement smoothed over the top to make a neat slope.

 

[Ambergreen45]

Sand and lime (without cement) is a little bit better since it will be more flexible at expanding/contracting with the heat and is less prone to cracking. Old chimneys were parged (rendered) with lime mortar (sand & lime).

 

[jack8]

Thanks for replies. That gives a decent idea how to do it.

Perhaps I wasn't exactly clear in my question but, I looked over the net and I found some instructions but they seemed conflicting so I was confused.

What I am also interested in, is apart from the micafil mixed with a mortar or sand/lime mix to pour into remaining cavities etc. is there also an option of using the micafil by itself, in otherwords as it comes out of the bag dry to fill the cavities and then do the mortar slope on top?

Cheers

 

[Nige F]

Old chimneys were parged (rendered) with lime mortar (sand & lime).

and most of it falls off

 

[Nige F]

in otherwords as it comes out of the bag dry to fill the cavities and then do the mortar slope on top?

Cheers

Not really - it`ll compress/move under the parged slope - get some cement in it

 

[jack8]

Ah, cheers for that clarification. I thought as much, I was probably just hoping for a lazy option Now I just have to find something big enough to mix all that micafil up in.

Thanks again.

 

[nickjb]

I just mixed it on a sheet of scrap plywood in the garden in a couple of batches and bought it in a bucket full at a time