Filling gaps in MDF false chimney wall

[airmeshka]

Hi there,

I've had a joiner build an MDF false chimney wall in my new house. There is some small gaps in some places that I'd like to fix before painting. Because the wall that the joists are attached to isn't 100% straight, there are also some gaps here as well that I would like to fill. Could you tell me the best way to fill these gaps, what type of filler is required please?

Many thanks

 

[AC Power]

Personally, I use autobody filler. It dries very hard, and quickly, and is VERY durable. Do NOT use drywall mud (AKA compound, plaster, etc...). Drywall/plaster cracks too easily.