Filling a fireplace rebate

[Gazzamuffin]

I have a cast iron fireplace insert and limestone surround that needs fitting. Everything fits in the to cavity no problem, but there is a 3 inch rebate built into the surround. That means when the insert is sitting flush with the inside of the surround legs there is a 3 inch gap between the wall and the back of the insert.

If the gap was quite a bit less I know I could just fill it with fire cement, but 3 inches seems like a bit too much.

Does anyone have the best way in which I can create a seal between the insert and the wall?

Many thanks

 

[Hogglet80]

I have a cast iron fireplace insert and limestone surround that needs fitting. Everything fits in the to cavity no problem, but there is a 3 inch rebate built into the surround. That means when the insert is sitting flush with the inside of the surround legs there is a 3 inch gap between the wall and the back of the insert.

If the gap was quite a bit less I know I could just fill it with fire cement, but 3 inches seems like a bit too much.

Does anyone have the best way in which I can create a seal between the insert and the wall?

Many thanks

Hi can I ask what you ended up doing please?