Blind fitter damaged cavity closer

[timmel]

Looking for thoughts and opinions on this please. Around a year ago I had a venetian blind fitted on my landing window which is on an exposed side of the house. The blind was fitted in Spring time and that Autumn I noticed that a leak developed at the two points where the blind was screwed into the underside of the window opening.

I've spent lots of time trying to work out what might have caused this as the blind fitter seemed very experienced and like a genuine guy, so was assuming/hoping he hadn't done anything wrong.

Anyway, I've decided enough's enough and I've cut out some of the plasterboard around the holes that he drilled to screw the blind in place. I've attached some pictures below, but it looks like he's drilled through the cavity closer which is now allowing water to seep in under heavy rain as it runs down the cavity of the house.

So my questions are:
1) Has anybody experienced this before?
2) If I seal it up with silicone, do you think that will sort the problem?
3) Should I report the blind fitter as he really should've thought about the possibility of this before getting drill-happy?
4) Any other suggestions to make sure I sort this properly so there are no more leaks.

Thanks in advance.

After cutting two holes in plasterboard:


Right hand side (obvious hole where drilled through):


Left hand side (smaller hole and doesn't leak as bad as right hand side):

 

[Gazman16]

Cavity closers are pvc with foam. That looks like a concrete lintel or block.

You will need to look above the lintel for the source of the leak, Can you add some pics of the outside above the window and the roof too?

 

[timmel]

That's a fair point, i'm using the term 'cavity closer' a bit loosely. It looks like it's some kind of DPM rigid felt-type material curved between the outside of the inside blocks and the inside of the outside bricks.

I believe the moisture is getting in in the first place because the wall is very exposed and some moisture naturally passes through the outer skin of brickwork.

 

[Bosswhite]

Going by the Pics, it dosent appear to be anything the person who fixed the blind did. There dosent seem any evidence of moisture around the holes.

 

[timmel]

Going by the Pics, it dosent appear to be anything the person who fixed the blind did. There dosent seem any evidence of moisture around the holes.

When it rained hard, water wiuld literally drip from the right-hand hole at a steady rate of approx 1 drip every 5 seconds so there was definitely water coming through the holes. This seems like a lot of water to be in the cavity but guessing this could be normal for a highly exposed westerly wall and my understanding is that this is the purpose of the make-shift cavity closer, to direct the water out through weep holes?

If these holes weren't present in the make-shift cavity closer, i'm guessing it woiud run out through the weep holes without dripping into the house? That said, the weep holes are virtually non-existant so that probably also isn't helping?

 

[swbjackson]

I'd say bad luck on the part of the blind fitter to have come across such poor construction. I certainly wouldn't expect to come across a bit of DPM that close to the plasterboard. I'd seal the holes with a good quality waterproof sealant like Adiseal and take it as a warning not to drill into the head of any other windows.

There's a good chance that these will perish in a few years and start leaking, at least you'll know what the cause of all the damp staining will be.