Help!!

[Lbarr]

We recently had our old wooden windowsill removed and the plasterers created a smooth skimmed windowsill and the whole rest of room plastered as well. All seems to dry out fine but when it’s rained heavy these damp patches appeared. Not had any issues with damp around windows before. Windows and plastics bone dry and can’t see any gaps outside in sealant. Any ideas? I’m very worried something hasn’t been done correctly

 

[Monkey Boy]

Your cill has not been sealed to the bottom side of the window frames.
it was always like that but the plaster now acts like a straw wicking moisture up.
you can seal with silicone use a heat gun to bend the nozzle putting sand inside it whilst you do it to prevent it collapsing that way with a curled nozzle you can get the sealant right up in the gap between cill and frame

 

[Cockney]

Put a window board back on.