Black mould advice

You need to clean the roof guttering on top of the wall. And paint the wall with damp paint and let it off for day. If that still the case then you need to put insulated plasterboard to fix the issue. I hope this helps

It would’ve been nice if myBuilder allowed photos on these threads but then again, they don’t make it easy on the job postings. Anyway, So what I understood was that behind the radiator, you’ve seen some mould patches This is only on wane wall where the radiator is and it is only along the bottom (i.e. alongside to where the TRV valves are) If that’s the case, my concern would be if any of the pipes (behind the wall, if any) are weeping. This has got nothing to do with the gutters (different positioning) In this case, check if you are loosing any pressure on the heating system Other scenario is that you may have a bit of rising damp This could be from the floor (radiator pipes under the floor) or, It could be if the external ground level is higher than the internal floor In this case you may need someone that deals with damp proofing to (at least) have a look at it and advise. Hope you get it sorted

Hi Mould is usually due to condensation which is likely caused by inadequate ventilation . To help prevent this, I tend to utilise “Wallrock” A thermal insulation material Works wonders Have a look on line Good luck