Retrofitting a Cavity Tray with an awkward roof height

[Gigante]

The house I bought at the end of last year has had an extension built around 2-3years ago, however it seems when they built it they failed to fit a cavity tray.
We're getting damp patches forming right underneath the lintel and on the edges of the wall that support the lintel.

We've been told that fitting a new cavity tray will be awkward due to the height of the extension roof and the location of the first floor window sills (there is only one course of bricks between). One builder has suggested a "vented lead flashing solution" but I cant see how that will resolve our problem as it seems the moisture is travelling down the inside of the cavity rather than between the extension roof and original wall.

Is there any other solution, would it be possible to only fit the cavity tray between the windows?

 

[23vc]

That painted brickwork doesn’t look like it’s likely to let a load of water through, could be wrong tho!
Do the wet patches correspond to window positions/window edges/area where no windows?

 

[Gigante]

Yep, the damp patches are right under the edges of each window on both sides.

 

[Celeronmanuk]

I'd first be checking where rain could be getting in around the windows. I can't see it penetrating the painted brickwork.

 

[23vc]

Could be getting in at the edges of the concrete cills. Is the entire perimeter of the window sealed to the brickwork at the sides and the concrete cill below? Does the cill have a drip groove

 

[Celeronmanuk]

Next doors downpipe needs sorting

 

[Alastairreid]

Check the gutters on the main house 1st.

 

[Gigante]

Could be getting in at the edges of the concrete cills. Is the entire perimeter of the window sealed to the brickwork at the sides and the concrete cill below? Does the cill have a drip groove

the cill on the left window does seem to have a drip groove and from my untrained eye does look like it’s sealed all the way around. The right window is a little harder to check without getting on the roof.

Check the gutters on the main house 1st.

the gutters do have a constant drip/dribble right outside the left window, we’re getting them fixed as well.

Just want to make sure we’ve covered all bases as we’re planning on renovating the extension and don’t want to end up with water coming through newly our decorated room.

 

[23vc]

I’d do some hose testing around various points

 

[^woody^]

would it be possible to only fit the cavity tray between the windows?

If need be that is exactly what you would do, no need for one below the cills.

Check the flashing and cill reveal joints first.