Cracked and loose plaster above windows

[ClaireRan133]

In two of my upstairs bedrooms, front and back, the plaster is cracking and coming away from the brick. I don't know what's causing it. I've had 3 builders give me 3 different reasons. The first said condensation and the Windows need trickle vents. The second said the bricks above the Windows need repointing. The third has said that it's the dpc? it's not working and allowing penetrating water to collect on the lintel and soak through into the house above the window. He wants to remove 3 courses of bricks and fix it so the water drains back out towards the outside of the bricks (my poor explanations of what he said).

I'm not sure who is correct. I'll attach some photos if anyone can please help. The dark patch in the first photo where the plaster is missing, is not damp it's like a rubbery glue like substance. The plaster never feels wet and we don't see any water dripping - except on our glass from condensation. The cracks are only in the recess of the window, nothing on the wall around the lintel. Thank you

 

[Jurassicspark]

In two of my upstairs bedrooms, front and back, the plaster is cracking and coming away from the brick. I don't know what's causing it. I've had 3 builders give me 3 different reasons. The first said condensation and the Windows need trickle vents.

Could be the case. Have you got a humidity meter?

The second said the bricks above the Windows need repointing.

Pointing looks good. Not the problem.

The third has said that it's the dpc? it's not working and allowing penetrating water to collect on the lintel and soak through into the house above the window.

You mean a cavity tray? I don't see a lintel in your picture.

I'm sure someone more knowledgeable in this field would advise you further.

 

[ClaireRan133]

@Jurassicspark thank you, yes a cavity tray! I'm sure that's what he meant. So you think that or the condensation is the problem... I don't have a humidity meter, but I have a loft PIV installed as the Windows do get a lot of condensation. Part of the problem is I have a large conservatory on the back of my house, which means a very expensive addition of needing scaffolding... So I want to be sure the 3rd builder is right about the tray, before I have to spend the money. Thank you for your help

 

[Jurassicspark]

The window looks like it's not really sealed properly. A weatherproof and UV resistant sealant around the exterior window joint might help resolve the issue.

When were the windows installed?
When did the problem occur?

 

[ClaireRan133]

@Jurassicspark I've only just brought the house, but I believe the Windows were installed 2012 and it seems like it's been an ongoing problem we paid for a level 3 rics and we've found the surveyor hadn't identified a few problems so....