Supporting sagging ceiling joists.

[gdickin2]

Hi.

I have taken on a pretty challenging renovation project of a victorian end terrace. The ceiling if flexing in the 2nd bedroom (approx size 12'x9'). The flexing is definitely the ceiling joists and they are very small, I would say they are less than 3"x2".
I think I will ultimately need to underboard the ceiling but can't go to the expense of tearing the old ceiling down and also replacing all the joists.
I am considering propping the ceiling in the middle to lift and support it and then adding additional support to hold it up. What options do I have to add support?
Ideas I had some up with were:
1. Bolting 4"x2" to the side of the current joists.
2. Running some 4"x2" beams across the top of the current joists (supporting properly at ends) and tieing the old beams to these cross beams.
3. dropping some ties down from the main roof joist (don't know what it's called but it's very thick) which runs across the roof at about 18" above the ceiling joists.

Any preferences or other suggestions?
Is it acceptable to underboard with 9.5mm plasterboard to keep weight down and make it easier to manhandle?

 

[mac391]

The timbers supporting the roof structure (usually 2 running from one gable end to the other) are called purlings. They support the rafters.


some ceilings are supported by these purlings but not always so in theory it could be possible to add thicker timers on top of original but probably a bad idea.

Problems are :
1, you are adding extra weight, by putting 4"x2" on top that it may not take,even if supported elsewhere.
2, your original sagging timers offer no support, they are there to hold your ceiling up (nothing more)
3, The timers have sagged over a long period and will never straighten out.

Only way to do it in my book is to remove and replace with 4 x 2.
The materials arn't expensive, you only need timbers, plasterboard and thistle, approx £2/300. Labour costs slightly different though.

None of your suffestions will straighten the ceiling out

 

[noseall]

If you have room for maneuver then adding a mid-span ceiling binder would be the best remedy. This could be say a 200mm x 50mm or a 150mm x 75mm timber beam. This would span from wall to wall above and at right angles to the existing ceiling joists then it is a case of propping each joist and fixing it to the binder.

I would not recommend fixing to any of the roof timbers as these may not only be fully loaded but any flexing of the roof will lead to flexing of the ceiling.