Sagging joists

[23vc]

Hi
Overboarding a 60s landing ceiling and notice it's pretty wavy, looking in the loft some of the ceiling joists have a gap between joist and binder up to 3/4" gap on some of them (also joists are sistered at this point under the binder), not sure if I need to stop and look at propping and strapping to binders or whether this is fairly normal over time and I can crack on. Doesn't look like there's been any movement recently but the loft is boarded and may have had a fair weight in it. Any advice appreciated!
Cheers
John

 

[23vc]

Meant to add, I can see the big old 4" nails holding the joists to binder so it's definitely all attached

 

[noseall]

You'll struggle to clamp them up tight now unless you can release the nails or fully access the connection and get some sash cramps on it. It may be possible to say pop an acro directly underneath the joint and add pressure then go up top and give the binder a whack with a lump hammer.

Once the gap is closed use long screws or angle brackets or hangers to fix together.

 

[noseall]

PS it may be the right time to add a stronger CB as the older ones were somewhat underpowered.

 

[23vc]

Thanks noseall
I don't think it's too bad and checking with a straight edge I think the boards are sagging as much as any joists so I think I'll take my chances and keep the weight in the loft off the middle, really don't want to start moving joists as I've skimmed all adjacent ceilings in the other rooms (same joists running through) and every screw will pop
Cheers