Ceiling joists, worth replacing?

[Lewis44]

Hello,

Currently renovating a 1950's bungalow, in the middle of deciding what to do with these ceiling joists and would appreciate some advice/opinions. We've taken down some of the ceiling boards and have noticed a little rot on the ends of a couple ceiling joists, and also noticed some of the perpendicular ceiling joists (as it's a hipped roof) look like they're clinging on for life by a single nail (See pictures), the joists are also not very level currently to screw boards onto.

The current ceiling joists are 3x2s. I would have gone ahead and replaced them with larger joists already, but this means having to temporarily support the purlins with acrows, modify the purlin bracing to be shorter and move the floor binders up slightly. Naturally hesitant to do that as I've not done it before.

Our future plan would be to have a loft conversion, as my knowledge goes, the loft conversion floor would be completely separate and suspended on new rsj's/flitch beams, so condition/strength of existing ceiling joists shouldn't be any issue? (or am I mistaken)

So my question is, do we keep existing ceiling joists and just do necessary repairs for the couple with rotted ends, and screw the dodgy looking ones hanging by a nail to kind of pull them/strengthen that connection? or is it worth the effort/hassle to replace?

I have attached images which hopefully give a good picture of what's going on.

Thank you very much for any advice!

 

[Wayners]

Our bungalow we took roof off. Cut the timbers I can see in your picture off with chain saw. That took two days.
Crain on new bespoke roof took a day.
Felt and batten roof took a day.
Dry then. Was easier to do that with our loft conversion. Cheaper as well.

Re you timbers.
To repair.
I've proper up timbers and put cross straps on loft side to straighten out. Amazing how well that works sometimes.
Bolted sisters timers (to the side) and replaced some.
Do what you can to repair

 

[robinbanks]

If you're going to convert the loft, why not fit the floor joists now, while you have everything open and ready to go? Would you want to be taking the extra depth you need from the rooms rather than the loft space..?