Should I use high strength mortar to fill this crack?

[Gary111]

The rest is black ash mortar, it came out very easily along the crack.
I wondered if I should use some special mortar to fill it prior to plastering and probably using a tile backer board.

Thanks

 

[tell80]

You say you wondered - well, looking at the pic - so do i.

 

[A Trowel]

No

 

[noseall]

The rest is black ash mortar, it came out very easily along the crack.
I wondered if I should use some special mortar to fill it prior to plastering and probably using a tile backer board.

Thanks

Not especially, no. Just regular 4:1 will do, but make sure you wet the B'Jesus out of it first. Looks like it may benefit from a bit of galv angle in that corner.