Screws becoming proud in roof

[Rob_Quads]

We finished our extension around 9 months ago now but recently have noticed something I don't quite understand.

It looks like the plaster is being pushed out in places. It always lines up with one of the screw heads.

I could understand if it was indented due to the roof falling down or something but what might cause what I am seeing?

I wondered if somehow water might be getting in somewhere but I can't see how water would get into there as those screws are into the joists.

Any ideas?

Some photos of a couple I found this morning.(Already repaied 4 from yesterday)
View media item 25113 View media item 25114

 

[noseall]

Looks like the heads are popping.

Not all joists are the same thickness and some are bowed. This can result in the plasterboard being pulled up in places and sometimes the board pops back and results in the fixing heads popping.

Or, it may be that the timber has shrunk/seasoned and the fixings haven't!

 

[freddiemercurystwin]

Or were they nails ..........

 

[Rob_Quads]

Or were they nails ..........

They weren't

 

[Blagard]

I think this type of problem can also happen if the screw itself was either not driven fully home or driven in tearing the the paper at the edge of the screw head.

It is in any event, a result of subsequent movement of the board in relation to the screw head. A fairly common snag and not one to worry about unless its happening all over!

I am not sure if just filling over it will be the solution. - Someone with more experience of this snagging item may be able to advise the best way to make sure it does not re-occur. For just a couple of isolated ones I would be tempted to just remove the screw and fill!