find cause of mould to solid internal wall?

we have an old house which has been extended so one of the original external solid brick walls is now an internal wall. the wall was treated by the preivous owners for damp with injection and sika render about 10 years ago. the plaster to this area is blowing and is slightly damp between the plaster and the render. there is also a type of mould which looks like very fine plant roots which i have treated with a chemical but this has now re-appeared. it seems that the only places this happens is where the treatment was originally carried out. any ideas on how to cure the mould or where to start to find the problem. there are no old pipes and the roof is sound so would suggest comimg from below
Chris Emmett, January 2010


done
Sounds like DRY ROT this has root like mould (white?). It needs to be treated very quickly as it spreads through releasing spores into the air. My dad had to get the whole house treated because of this.
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Davie (roofer), March 2010
HI, sounds like you have rising damp.
I would suggest having a look at the damp proof course. if it's an old house then the DPC will probably be of slate, which breaks down over a long period of time.
you can buy a damp-proof injection kit from DIY centres and if you are handy with tools etc. have a go yourself and save a few bob.
Hope this helps.....Dai

bandydai, February 2010