I have a mould smell coming from my downstairs bathroom.At first I thought it was the neo angle shower stall tore it out knocked a hole in floor checked plumbing and had 2 plumbers come in said it was'nt the plumbing.I tore wall out can't see or smell mould back wall is dry.Ckecked stink pipe for blockage,and clear.Took toilet off,that's not it.About 3 months ago I caulked the outside wall so water would not run against house where the bathroom is.I discovered that I caulked over mortar vents in the brick so I took caulking out smell still there.Is it possible that the expansion joint could mould and is coming in through the mortar vent holes?Your help would be greatly appreciated as I have tried everything possible.