Plastering around gas fire place

[plaster1024]

Hello

I have a gas fire place which I have plastered around. I have used an aluminium C channel stopping bead around the fire place opening to get a nice straight edge. The manual for this fire place specifically states that you can plaster around it. Infact it has labels on the fireplace facia saying "GLUE PLASTERBOARD HERE".

I used fibreglass mesh tape around the C channel, including all corners. Then I base coated twice and finished with top coat.

However I am getting cracks around the top of the fire place where the base coat is over the C. I have measured the temperature of the channel, it is getting to about 90degC. The fire place is brand new, so I'm sure it's not faulty.

Is there a specific way plaster these types of fire places and stop this from cracking? A higher temp rated base coat maybe?

 

[malc]

Metal expands with heat and cracks the plaster. The manufacture of the fire told you to fix plasterboard here, It did not say 2 base coats with a plaster finish. The fire is not faulty .

 

[plaster1024]

they also told me to use a single sheet of plaster and cut out the middle for the fireplace window. Impossible to get a clean edge without a trim.

Is there anything I can use instead of base coat to stop it from cracking?

 

[Monkey Boy]

Tile it

 

[000]

they also told me to use a single sheet of plaster and cut out the middle for the fireplace window. Impossible to get a clean edge without a trim.

Is there anything I can use instead of base coat to stop it from cracking?

@ do as manufacturers say —Plasterboard bridges over the metal @ finish edge with thin coat @ skim -the end .,