Damp & Mould problem AFTER cavity wall insulation removed.

[McAhuna]

Our 1920s semi had a damp problem. Failed/wet cavity wall insulation was identified as the cause, so we had the insulation removed.

It was removed amid this damp winter and air-brick ventilation was installed on external walls to help it dry out in the longer term.

But now, after it has been removed we are getting terrible white mould flaring up on one patch of the living room wall. The damp patch is on a wall from which the insulation was removed. The mould patch is about 1.5m high, located above a radiator on the inside and an air brick on the outside).

Spraying this patch with anti-mould seems to have no effect, possibly makes it worse as it grows again in a few hours. See the picture - we scrapped off the wall paper as we though that it might help dry out, but has made no difference.

We are baffled as to the cause. Does anyone have any suggestions please?

 

[Alec_t]

Are you sure it's mould and not efflorescence?

 

[Mike13]

they possibly missed a bit when the cavity insulation was removed?

 

[McAhuna]

Are you sure it's mould and not efflorescence?

You could be on to something here. Thanks
Do you know how we tell for sure, or what is best to do about it?

 

[McAhuna]

they possibly missed a bit when the cavity insulation was removed?

Perhaps - but it is ironically worse now (on that particular patch) than it ever was when the insulation was present, so I suspect something else is going on.
Also, pre-insulation removal the mould was black. this white flowery stuff has only appeared post removal of the cavity wall insulation.

 

[Gasguru]

Looks like efflorescence...try brushing it off and with time as the wall drys the salts may stop coming to the surface.

 

[Harry Bloomfield]

You could be on to something here. Thanks
Do you know how we tell for sure, or what is best to do about it?

Drill a small hole through the mortar joint, from the outside, and use one of the snake cams to have a look.

 

[Alec_t]

Do you know how we tell for sure

If it's efflorescence it will likely contain fine crystals. Check with a magnifying glass or microscope.

 

[McAhuna]

Thanks all