not straight plaster on boarded-up old ceiling

[TofuSpaceship]

As the big building job we are carrying out is approaching the end, the builders had two plasterers round to plaster the big bedroom (original wall and boarded up ceiling).
The property is end of year 1800.

I am very pleased with the walls however I cannot say the same with the ceiling.
When the boards have been put up, already said boards were a bit wonky/humpy and not straight, allegedly because the joists are sagging a bit.

However expectation was that by plastering, everything would have been straight, which is not. If I take a six foot level and I span it in different directions across the ceiling, there is almost always short of an inch gap at one end.

Is this expectable in a boarded-up ceiling of an old property or could have they done a better job?
I can see it with my naked eyes at the moment, hopefully painting it will hide it, but would like to get some opinions before pursuing with the roller.

Cheers!

 

[pilsbury]

In my limited knowledge, it's the boarding that denotes the levels. Plaster skim is just a couple of mm thick and can't really be used to level out an inch

The only way I can think it could have been done better is to have leveled the joists with battens prior to boarding

 

[cdbe]

As above, or more likely level it with bonding first. So the answer is yes, they could have done a better job, but then it starts to depend on whether they were contracted to skim the ceiling or plaster it.....

 

[datarebal]

not a listed building is it?