Incorrect roof window flashing kit installed - how sketchy is it?

[tadas]

Hello everyone,

Some time ago I had major leaks/problems with one roof window. It got damaged by water quite a bit so we went forward with complete replacement.

Fast forward 9 months - roofer working on guttering told us that the new window is installed incorrectly and we may want to fix it.

Window: https://sunluxroofwindows.co.uk/tim...-pine-centre-pivot-roof-window-mk04-1051.html (or at least very similar)
Flashing kit installed: https://sunluxroofwindows.co.uk/vel...e-deep-profile-tile-flashing-78cm-x-98cm.html (see photos, quite obvious)
Roof is slate (again, see photos). Then there's this unusual use of silicone sealant..
I understand correct flashing kit for slate window should be: https://sunluxroofwindows.co.uk/vel...l-ck02-single-slate-flashing-55cm-x-78cm.html




Now question: how bad is it?
Original roofers claim "everyone has their own opinions, we did our job, window is not leaking". But it seems they were not following manufacturer recommendations.

I'm wondering if we should go ahead and replace it with correct flashing kit and make sure tiles are installed correctly (use of sealant suggest there may be some corner cutting involved).

 

[Vinty]

Looks like the original roofer has used a flashing unit for single lap tiles.
Your roof appears to be fibre cement slates which are double lapped and require soakers along the side of the window.
You would need a flashing unit for a slate roof.
Whoever installed the new window has used the wrong flashing for that type of roof.


If the appropriate flashing unit is installed properly there should be no further problems

https://www.yarddirect.com/velux-zwc-window-profile-set?sku=ZWC CK02 0000&gclid=CjwKCAjw2bmLBhBREiwAZ6ugo09fsufpHmLTHKeabhwrlOS0YLt2FwVhxyrfPxNuANAkn6GuLKJ9ohoCJu8QAvD_BwE