Dreaded damp patches on plaster... Any ideas?

[stevethespreader]

Moisture will travel by capillary action up the plinth. Capillary action will then pull the moisture that has travelled up the plinth behind the stop bead (which is bedded in S&C) to travel on and up behind the bell cast (which is also bedded in S&C) and so on up the wall.

you shouldent have render coming past the stopbead from the plinth if its done proper u should have a nice clean stopbead to sit ur bellcast on so there will be no capillary action going past the stopbead like you say, as it will be impossible for the damp to go past the bead because the render stops at the otherside of the stopbead also the render for the bellcast starts at the otherside of the bellcast so its nowhere near the render of the plinth https://www.youtube.com/watch?v=FSKwZk9GGV8 so look at the vid and yes im saying that the damp from the plinth render stops at the bottom of the stopbead

after watching that vid again it looks like hes using the stopbead and bellcast bead as the actual dpc because he has covered the old one

 

[roy c]

Check the pointing on the stone work above the window cill, also check the gap on the window frame and the revels. Just a thought, water may be getting in around these areas, Also you could put a hose on it from the bottom and move it across the wall slowly and take it up past the cill and spray it on the windows and revels and have someone inside to tell you when the wall gets wet .Make sure if you do this to start at the bottom and move up slowly... My guess would be pointing between the stone work...