plastering around gas fire place

plaster1234 · Post by **plaster1234** » Sun Dec 17, 2023 9:05 am

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?

dewaltdisney · Post by **dewaltdisney** » Sun Dec 17, 2023 9:55 am

I do not know for sure but it could relate to slight expansion through heat or the plaster was not thoroughly dried out and the heat has accelerated the drying causing cracks. So I guess you must work out if it is movement or drying that has caused your issue. I would think the first move would be a flexible filler in the cracks and see how that goes.

DWD

plaster1234 · Post by **plaster1234** » Sun Dec 17, 2023 11:04 am

Thanks for the reply - definitely not a drying out issue. I left it for days. A flexible filler may help - I will try that. Any other suggestions?

dewaltdisney · Post by **dewaltdisney** » Sun Dec 17, 2023 11:50 am

Am I right in thinking the C section is slotted over the plasterboard edges? Any metal will expand with heat and this may well have caused the cracks. My thoughts are that the initial expansion has already occurred so filling will hopefully stop any contraction and hold it stable with future heat and cool cycles. I may be wrong.

DWD

plaster1234 · Post by **plaster1234** » Sun Dec 17, 2023 9:17 pm

Thanks for the reply. I will try a filler. I’ve tried to find data sheets on some of the flexible sandable fillers sold here to understand heat rating but nothing comes up. Should I be trying to use a high temp rated filler? Or are most fillers rated for up to 100degc application?

dewaltdisney · Post by **dewaltdisney** » Sun Dec 17, 2023 10:05 pm

I do not know but I would have thought that plaster would cope okay, in the heat of summer 100 degree heat does not make plaster fail in my experience.

DWD

big-all · Post by **big-all** » Mon Dec 18, 2023 2:14 am

could it be a clearance issue as in 150mm clearance required ???
what does it say in the manual ??