mortar for outdoor fireplace?

[Mrs Ahab]

Hello, we are building an open fireplace with a chimeny in our garden, we have recycled solid red bricks and some bricks from inside storage heaters to line it with. Whats the best mix of mortar to use, the opening will be fairly big.

We are also going to build a 'hot tub' from a cast iron bath, bricked in with an opening for a fire to be lit underneath and a couple of flues at the back, shuld we be using the same mortar mix for this.

Any tips will be appreciated, we are total novices!!

 

[theprinceofdarkness]

Are you going to boil a missionary? What you are attempting is extremely fraught, as the bath will expand with the heat. The bricks will need to be kept dry, else when the fire is lit, water within the bricks will turn to steam and spall the bricks perhaps explosively. I built a brick barbeque, using lime mortar and it worked but you could see the cracks in the mortar as the bricks expanded and contracted.
Frank