boards sagging

[bagofjuice]

I've just gone into the garage and noticed the 12.5mm plasterboard I've been fitting these past few weeks are sagging in between the joists. The joists are 600mm centres. I've screwed at 400mm spaces.

Why has this happened?

 

[roy c]

Youv'e missed the joists with your screws!!!!

 

[Alastairreid]

Have the boards got damp?

 

[bagofjuice]

Roy, no screws missed. The sag is between the joists not along it. There are no noggins or support between the joists but I thought the boards would be ok over the 600mm.

Alastair, its a very cold garage as the temp has dropped but its a dry garage. The boards have been up for a week.

I used foil backed plasterboard if that makes a difference.

 

[roy c]

How far apart are your screws? Should be about 6" or even 4" on that span,It wouldn't have hurt to put some noggins in.What span are your trussses? I take it they are trusses that make up the roof? Foil back shouldn't make any difference on the fixing....

 

[kingandy2nd]

12 screws per board isn't enough IMO.

Also how did you fix? Did you screw one side, then the other, then the middle? Or did you fix one edge and then work across?

Are your screws flush with paper of the plasterboard or have you gone through the paper?

Also where did you buy the board from?

 

[bagofjuice]

12 screws per board isn't enough IMO.

Also how did you fix? Did you screw one side, then the other, then the middle? Or did you fix one edge and then work across?

Are your screws flush with paper of the plasterboard or have you gone through the paper?

Also where did you buy the board from?

Yes I screwed one side then the other to keep the board up, then filled in the middle.

Screws are just under the surface of the board using bugle headed plasterboard screws.

Plasterboard from Travis Perkins.

 

[roy c]

I've just gone into the garage and noticed the 12.5mm plasterboard I've been fitting these past few weeks are sagging in between the joists. The joists are 600mm centres. I've screwed at 400mm spaces.

Why has this happened?

I am sorry I mis-read your post when you said you screwed at 400mm spaces I misunderstood it So that is your problem. So make yourselves up some props and push the sagging boards up gently then rescrew them at 4"-6" spaces If you are careful you may get away with it and get the boards firmly fixed....Dont let the screws break the paper on the board...

 

[joe-90]

Still sounds like a damp issue to me. I think he might struggle to get them flat again.

 

[bagofjuice]

Here's a pic.

Untitled

• bagofjuice
• 12 Jan 2013
• 1

If it was damp then surely if would affect all the boards?

...push the sagging boards up gently then rescrew them at 4"-6" spaces If you are careful you may get away with it and get the boards firmly fixed...

I'll give this a try.

 

[joe-90]

That's hardly anything. Just need a few more screws. Thought you meant it was sagging in the middle.

 

[stevethespreader]

in my opinion the board is not supported enough and you should have put some noggins in like roy said, if that ceiling is to get a skim it wont be long before you have a nice long crack down it

 

[cajar]

It looks like one screw in between the two edges of the plasterboard ie with the screw going into the gap between the two edges instead of one screw going through each edge of plasterboard itself about 5mm from the edge. That could possibly be the problem, with the screw not having any lateral grip on the board in fact pushing it to sag.

 

[kingandy2nd]

Yes I screwed one side then the other to keep the board up, then filled in the middle.
.

I don't think it looks too bad from the pic, but the resolution doesn't give away much.

I think the above bit is your problem. Boards do have a little natural sag to them, so you need to work across the board when screwing it in, start one edge then move towards the middle while pushing up the plasterboard to the joists as you fix it to straighten it out. Work across the board from one edge to the other like this.

By screwing one edge, then moving to the other edge and screwing that in you are effectively trapping the natural sag in the middle of the board.

 

[roughcaster]

To give us a better view of the "sag" in the boards, hold a straight edge across the sag and then take a photo.
For my tuppence worth,,, nowhere near enough screws from what i can see, and the more timber/noggins to fix to, the stronger the job. There's a lot of weight hanging overhead in a sheet of 12.5mm plasterboard.