Have a bit of a damp patch that appears below a downstairs window after heavy rain. I checked the window sill outside and the wee groove underneath it (That I guess the water is supposed to run to the end off and out down to the ground?) is blocked up at both ends with concrete, or maybe the groove was never formed well when the sill was cast.

Anyway, is this likely to be the culprit?

Options?

Possibly – remove the concrete and see what happens. Or it could be running down the frame if it isn't sealed well.

It could well be, thats specifically designed to cause the water to drip off.
When I made a window sill once I didnt add one & had lots of penetrating damp …doh!

As above remove the stuff bridging it & see what happens. You can paint a silicon solution on the brick work which should help stop rain blowing through the wall.

I think I may have seen that film, its the one with the plumber no?

>You can paint a silicon solution on the brick work which should help stop rain blowing through the wall.

Downside of that is it prevents the wall breathing to the outside if it's getting damp from elsewhere, and you shouldn't really need to.