Plasterboard under en suite wall tile black and soft

Hi, just replaced a wall tile in the En Suite and the plasterboard behind was black (presumably mould) in places and softish. Am I right in saying that this is bad news or is it in anyway normal for a shower/bathroom. The tile is away from the shower so wouldn't be anywhere that'd normally be getting wet apart from condensation. Thanks in advance.

yep i would say you are correct. Get it sorted as if it is an en-suite and leaks you may ruin 2 or more rooms before replacing it. And then you will be really cheesed off. Gut a second opinion from a builder you can trust.
Why did the tile lift?

does the en-suite have any rapid ventilation mechanism... ie an openable window or a mechanical ventilation system??

nelly said:

Get a second opinion from a builder you can trust.

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Yeah, sounds like a plan.

The tile didn't lift, was just replacing it as there was two holes in it from a fitting the previous owner took with them.
Theres no evidence of leakage anywhere as far as I can see though. Floorboards are fine. Ceiling downstairs is fine. The en suite is vented and has a window so is quite airy and doesn't stay damp for long after the shower is used.

Check any pipes that run behind the wall for leaks ata joints etc. Is the wall behind plasterboard and skimmed or is the tile and grout applied directly on to the plaster board? If there is no skim the plasterboard should be a green colour, as opposed to standard grey. The Green board is moisture resistant plasterboard.

Niallman said:

Yeah, sounds like a plan.

The tile didn't lift, was just replacing it as there was two holes in it from a fitting the previous owner took with them.
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that could be your answer then, the moisture and water splashes could have been getting in there.
If its possible to lift the tiles that are around the problem one, you would be able to see if the problem is confined to that area alone.
If it is then scrape out the mould rotten plasterboard till your past the contaminated area then treat with a good anti fungicide, seal and replace tiles. Jobs bisto.
Otherwise if problem is larger than this area then I'm afraid you are going to have to replace the lot. sooner than later IMO