Originally Posted by maltoftheearth
I have not had a stuck fermentation yet with BIAB but I noticed by searching that others on this board have. Just a thought, I am new to brewing so I would be happy to hear whether either of these thoughts are valid or not and why. Thanks.
Stalled fermentation can be caused by many things such as yeast health, pitch rate, mash temperature, etc. Can you provide some links that show a correlation between stuck fermentations and BIAB?
When it comes to "pitching on a yeast cake" I'd be more concerned about not washing the yeast and massively over-pitching. This thread may be useful to you. http://www.homebrewtalk.com/f163/why-not-pitch-your-yeast-cake-166221/
If you still want to rack new wort onto an old yeast cake then you can either swirl the fermentor as you transfer the wort or gently stir the sediment on the bottom after transferring.