I recently removed some ugly tiles from the wall (on the ground floor) in the photo and paid some guys to do cement rendering. A few weeks later I put a clear masonry sealer coat on it. Then the rains started and some damp patches are showing. The other side of the wall is in the neighbours garden. I attempted to draw a pic (of the outside) on the post it note to show that theres a small ridge with a 15cm flat part and they have electric wiring on top of that. I think thats where the water is entering. 

 

I was thinking of painting the inside with TOA roof sealer. Could I use that on the outside as well. Or should I lay concrete on the top of it. 

 

If I do nothing whats going to happen with this 40 yr old wall. ie if I put a coat of the TOA roof sealer on it and maybe another coat of dulux what will happen over time if I dont fix the outside to stop the problem?

 

With so much rain now I think I will wait until december to do the outside. 

 

 

You need to fix on the outside as if you only fix on the inside,

the water will still enter the wall and over time weaken it,a

quick fix   for the time been would be to buy a roll of Butyl

rubber it's about 5 inches wide and sticky on one side,just

stick it on the wall and down over the the ledge and wiring,

so the rain runs off.

 

I have been fixing some leaks on the roofs of my properties

only temporary until the rains stop.and it works very well.

it was a 160 thb for a roll,so a cheap fix for you.

regards worgeordie