rain marks on exterior wall

[vansbest]

Hi, my father in law lives in a second floor flat. His neighbour below has been complaining about water appearing on the interior window head. Her window is below but offset from FIL's window. I have checked his window and someone has filled in the underside of the wooden cill with mastic and covered the drip groove. The window cill is hardwood and in good condition. However to one side of the concrete cill the roughcasting below the cill end is rain marked and black.. His neighbour below has weep vents above her window ( i would reckon a couple of course above her lintel) and these have been filled with translucent silicon sealer. Is it likely that the neighbours leak is from my FIL's window? And also what is the cause and solution to the 'rain marking on the roughcasting.
many thanks

 

[KenGMac]

vansbest, hi.

My alarm bells are ringing.

The "black mark to one side of your FILs window are probably being caused by the dust accumulation on the glass of the window being "washed off" by rain and in doing so it is running onto the sill, the sill is possibly slightly off level that is forcing the rain water off to one side or another. I assume that the roughcast is "white"?

As above the "alarm bells" that I am aware of is that you note in your post that the weep holes above the neighbours window lintel have been filled with a clear mastic, bluntly not a great idea.

The weep holes that have been filled with clear mastic are there to be left clear and NOT BLOCKED OFF !

These weep holes are designed to allow any build up of water / moisture / condensate / penetrating rain water to be evacuated from the cavity. The weep holes are the only "outward indications" of a "Cavity tray" that is specifically engineered for this purpose. as they are blocked up with a clear mastic, then any water from wherever within the cavity WILL find another outlet, in this case it could be into the neighbours home.

Hope the above is making sense?

Ken

 

[Alastairreid]

Bottom line, tell the neighbour to get the weep vents cleared.

And check your gutters are not leaking and hitting the cill.

 

[conny]

Also clean out the mastic from the drip channel to allow any rainwater to 'drip' from the cill rather than track across to the wall.