Mystery leak in Roof between Velux Windows

[johnny2007]

Might sound stupid, but i fell for it many moons ago.
Is the velux window fully closed?
They have a "ventilation" closing position which looks like it's closed but it's not.
My roofer friend laughs about it every time he sees me for that time I called him to shut a window.

 

[Gary Daines]

Might sound stupid, but i fell for it many moons ago.
Is the velux window fully closed?
They have a "ventilation" closing position which looks like it's closed but it's not.
My roofer friend laughs about it every time he sees me for that time I called him to shut a window.

Thanks for the reply

these are top hung windows and the ventilation option doesn’t seem to be the issue. I don’t want to embarrass myself because I don’t really know, but there’s no wetness or evidence of any water on or next to the Velux whether the vent is open or not

the water seems to be collecting in the middle of the ceiling between the two windows and then running down to one side

how it’s getting there is stumping me but there’s no evidence that I can see of it coming in directly via the window

 

[datarebal]

would there be any reason against me attaching some new flashband over the join between the existing felt and lead at the top of the roof where you have highlighted? If the problem lies there I wonder if that could be a solution?

No reason not too.. prime it first.. best bet get the felt roofer back to look.

velux opener, first click is vent it does not change anything on the out side. if it leaks when open to vent ...the window is wrong or damaged

 

[Gary Daines]

No reason not too.. prime it first.. best bet get the felt roofer back to look.

velux opener, first click is vent it does not change anything on the out side. if it leaks when open to vent ...the window is wrong or damaged

thank you

I might give that a go

he’s out of the country unfortunately. He said he’ll come have a look when he’s back in September but I don’t really want it getting worse it there’s anything I can do in the mean time

yeah, I can’t see any issue with the vent on the Velux. There’s doesn’t seem to be any water coming in directly from the window, the window frame or the vent so I think the window itself is ok

 

[datarebal]

Flash band will only be a sticking plaster, but should help prove a point or not as the case may be.

 

[Gary Daines]

Flash band will only be a sticking plaster, but should help prove a point or not as the case may be.

thank you

yeah ok, if it helps me narrow down where the problem is that will still be a help

although on the Bostik website it states the life expectancy of their flashband product is 15 years?

 

[Alastairreid]

It may have been leaking since the loft was converted but is only showing up now as the membrane at that point can be failing.

 

[datarebal]

i would not bank on that..
be sure to take it down over the edge a bit...and prime it all

flashband that is

 

[Gary Daines]

It may have been leaking since the loft was converted but is only showing up now as the membrane at that point can be failing.

that was another thought I had

I assume the membrane is the second layer of defence? That water is not supposed to get to the membrane but if it does it should still protect it?

So if the membrane has failed i need to resolve the fail in the membrane but also still find the original source of the leak and rectify that?

 

[Gary Daines]

i would not bank on that..
be sure to take it down over the edge a bit...and prime it all

flashband that is

Thanks

yes, plan on priming it first and making sure the flashband covers the join between the felt and the lead (and past the join in both directions)

 

[Alastairreid]

that was another thought I had

I assume the membrane is the second layer of defence? That water is not supposed to get to the membrane but if it does it should still protect it?

So if the membrane has failed i need to resolve the fail in the membrane but also still find the original source of the leak and rectify that?

I pointed that scenario out as any faults in the original job may not show up till long after the contractors have gone.
The membrane is your second line of defence but will not keep rainwater out indefinitely.

 

[Gary Daines]

I pointed that scenario out as any faults in the original job may not show up till long after the contractors have gone.
The membrane is your second line of defence but will not keep rainwater out indefinitely.

Ok I understand what you mean

thank you

 

[Gary Daines]

I pointed that scenario out as any faults in the original job may not show up till long after the contractors have gone.
The membrane is your second line of defence but will not keep rainwater out indefinitely.

Thank you

If I was able to figure out the cause of the leak and remedy that, would I also need to replace the existing membrane if that had failed?

Or would it be ok to leave it as is if the leak was fixed?

 

[Alastairreid]

If you are confident you have the leak solved then the membrane is defunct.
Belts and braces really.
Plenty of roofs have no underfelt or membrane.

 

[Gary Daines]

If you are confident you have the leak solved then the membrane is defunct.
Belts and braces really.
Plenty of roofs have no underfelt or membrane.

thank you