Replacing or repairing joists

[Andyk78]

Just ripped out bathroom suite and taken room abck to bones and come across 2 rotting floor joists as pictured. The rest are ok just these two from under the bath.
What the cheapest quickest way to sort them out and how do I go about it?
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[dann09]

Research on here. This exact topic with similar pics has been covered many times: eg look at the bottom of this page for "Similar Topics" and each of them will lead to similar details.

Knock off the plaster for 300 - 400mm ht. Look for white strands. Altho it appears to be purely wet rot.

Expose and examine the next joist - under the partition - as far as possible

You will have to cut the joists at least 300mm beyond any sign/discolouration of rot. Using a circular saw (and perhaps, a reciprocating saw) cut small segments out at a time.

Carefully remove the debris or you will damage your ceiling.

You must leave in enough sound joist for bolting-on to, or remove the joists in question, all the way to the opposing wall.