Damp after repairs

[derekphl]

A few weeks ago, I made some repairs to a few external cracks in the render on my house (c. 1900's, end of terrace type).

There has not been much rain in the time since (UK, South East) but there has been mould/damp marks coming out on the inside walls where I made the repairs, on two separate areas of the house since then.

The bizarre thing, apart from the timing which may or may not be coincidental, is that I made repairs to the top part of the house where the cracks were, but the mould growth is in some areas right down to the bottom of the walls inside.

It is as if the moisture now has no where else to go but inside the house which I'm not sure is plausible, especially with the speed at which it has appeared in two separate areas. I can't think of anything else though, so any clues from anyone out there would be greatly appreciated.

 

[peaps]

A few weeks ago, I made some repairs to a few external cracks in the render on my house (c. 1900's, end of terrace type).

There has not been much rain in the time since (UK, South East) but there has been mould/damp marks coming out on the inside walls where I made the repairs, on two separate areas of the house since then.

The bizarre thing, apart from the timing which may or may not be coincidental, is that I made repairs to the top part of the house where the cracks were, but the mould growth is in some areas right down to the bottom of the walls inside.

It is as if the moisture now has no where else to go but inside the house which I'm not sure is plausible, especially with the speed at which it has appeared in two separate areas. I can't think of anything else though, so any clues from anyone out there would be greatly appreciated.

I would suspect the plaster you used was gypsum based? If so this is your problem. Make sure you have sorted out the water problem before you go further.

 

[derekphl]

The repairs I made to the outside were with a mortar render.

 

[Possel]

The repairs I made to the outside were with a mortar render.

And what was the mortar made of? Cement (=gypsum) or lime? Lime would help the wall to breathe (and so the moisture can evaporate) but cement seals it in if it gets behind/through the render. I'll bet the original house (at that age) was in lime and so you should use compatible materials or else all you do is to chase the dampness around and never get rid of it!