i found a mushroom growing through a joint where my shower meets a skirting board. what should i do

Fry it with some eggs & bacon ;)

Hi madmaxwell, It sounds like the gap between the skirting/shower has been wet for a while, or the shower has been leaking a while underneath, waste etc....This may just be wet rot but it could be worse dry rot... you need a builder to come and evaluate.

You either have a leak from the shower or a damp problem. these need to be addressed before the problem will be solved. Once the damp has gone a fungus killer or frying pan would work!