How bad can a wall be for skimming to be an option

[STI]

Hi, need advice please. About 8 years ago i had our lounge skimmed. On one wall we have a log burner. About 2 years ago we noticed hairline cracks spreading across this wall. We put this down to the heat from the burner, so we decided it is time to redo. When i started to look more closely i noticed a lot of the skim had blown. I have now started to remove the blown plaster skim. However this has now left me with a wall that is in part back to the original plaster and in part still with the solid skim in place. A patchwork but the solid skim is in whole sections not just little "islands" on the wall

Can a plasterer reskim this wall in this condition or does every bit of the old skim need to come off even if it is still solid?

Thanks for any help and advice.

 

[Pharun]

I did my bedroom a few years ago after taking the previous owner's wallpaper off and the skim just shelled off in large patches , there were large cracks where the electrical conduit was and where there had been a bit of movement, I scraped all the loose plaster skim off and PVA'd the whole wall and where there were cracks I applied some fibre tape scrim and brushed it in with the PVA, I allowed that coat to set, I gave it another coat of PVA and as it was going tacky I mixed up some multi finish and filled out the area where the skimming had shelled off , I then re-skimmed the whole wall, that was over ten years ago and no cracks have reappeared, and the finish is sound, providing your backing plaster is still OK then an over skim is fine

 

[STI]

Thanks for this, sorry was offline all day yesterday filling cracks. All sounds good the backing plaster is sound although i found 1 or 2 protruding nails from old picture hangings i guess, now removed. So thanks for the re-assurance.