Wet plaster smell after rain

[ABC2020]

For a while now we’ve had a wet plaster smell persist throughout the right side of our house after it rains. We only experience this smell on the side of the house that was extended before we moved in. It can be smelt on both levels at the front and back of the house. Strangely there is no sign of damp on any walls or ceilings and we’ve had a moisture check that didn’t flag anything significant. We’ve had a number of explanations but not thorough investigation (which is likely to be needed). Some of these have been a plumbing issue in en-suite, outdoor waste pipe (it doesn’t go above the roof and does a 90 degree turn below fascia so smell could be coming in although it’s not a sewage smell we are experiencing), water getting into cavity, loft not properly ventilated. I can’t get into the loft on this side of the house as there is no access but I can see there are no soffits in the fascia so I am going to try that. I know others have posted a similar thing but I just wondered if anyone has any other ideas?

 

[dontbelieveawordofit]

what type of roof/ materials on the extension?

 

[ABC2020]

Photos attached.

 

[ABC2020]

For info - the extension went into the loft at the back of the house but not at the front - the front does not have access so I can’t see if water is in that part and possibly rotting insulation or something else if that is the issue. Smell has definitely got stronger upstairs and downstairs.

 

[scottburnettuk]

Hi, we have the same issue. We had a leak a few years back in the bathroom, leak was repaired, ceilings below ripped down and re-plastered then treated and re-painted but we now get a horrid damp plaster which is worst when humid. Can't even sit in the room as the smell is awful and it gets on your throat. Did you manage to resolve your issue?