Velux window experts – Repair or replace?

Noticed some water coming in, in our attic space recently in the recent heavy rains. It looks like it’s got to be coming from the Velux window. It’s probably fairly old now.

Anyway, it has blackening in one corner, and I just lifted some screwed in trim on the edge which came away easily as the wood under there is rotten and sodden.

I’m not 100% that the leak is happening there, but obviously it’s the most likely.

I could probably replace any woodwork myself, but is there likely to be seals and all sorts that need doing? There doesn’t look to be a seal as such which drops onto this section of the surround, more that when you close the window, the profile goes under the upper profile and the water should drop off the side and away down the roof.

The screw holes themselves could potentially allow some water in to the wood beneath I suppose but I’m not sure that the water should be reaching where the screws are in the first place.

thumbnail_IMG_20191108_104345 by blackteaonesugar[/url], on Flickr

thumbnail_IMG_20191108_103249 by blackteaonesugar[/url], on Flickr

thumbnail_IMG_20191108_110858 by blackteaonesugar[/url], on Flickr

thumbnail_IMG_20191108_110904 by blackteaonesugar[/url], on Flickr

thumbnail_IMG_20191108_110850 by blackteaonesugar[/url], on Flickr

Anyone renovated some Velux windows and have any advice to offer, or is it a dead horse, and replacement is the only real option?

Weird place for a leak. Are you sure its been fitted with all the right gaskets and trims?

You could definitely rebuild the frame if you had the time, the energy and a decent workshop. But could you be sure of solving whatever leak has been allowing water to penetrate there for years?

Just replace it. The DG unit will start to develop condensation soon because by now the atmosphere inside the gap will be pretty damp.

For starters it looks like your tiles are under the edge of the velux ‘skirt’ on one side. We had this and it caused a leak into the loft.

For starters it looks like your tiles are under the edge of the velux ‘skirt’ on one side. We had this and it caused a leak into the loft.

No, the skirt is deffo under the tiles at the top and sides. On the downward side, the skirt is above the tiles so water drops onto the tiles.

Just replace it. The DG unit will start to develop condensation soon because by now the atmosphere inside the gap will be pretty damp.

Only if the seal on the DG has failed – and it doesnt look to have it might in the future – but so might a new one – that alone is not a reason to replace.

What the photos show – id probably replace it because they really are not that expensive for what they are VS the cost of getting the repair wrong

Yeah the opener part of the window looks to be fine. No damp or anything.

Just had a provisional quote for £1150 large to replace it.

cause condensation running down glass onto wood over time.

I’d replace that

look at improving the room ventilation and open the window more

Only if the seal on the DG has failed – and it doesnt look to have it might in the future – but so might a new one – that alone is not a reason to replace.

The seal doesn’t fail; what happens is that moist air is able to enter the gap through the tiny holes in the separator; it’s designed like that to deal with changes in atmospheric pressure. Every time the air pressure increases a few molecules of moisture enter then stay and eventually the moisture level reaches the point where condensation begins to appear. The DG unit is then said to have “blown”. It’s inevitable with time.

No signs of moisture at all in the unit. It’s fine.

It’s not condensation, as it’s an attic room, very dry otherwise (no bathroom near it) and it never looks to have much condensation on it.

Plus, it was pissing down the other day and the water is coming in then, finding it’s way onto a big wooden beam beneath the window and dripping onto the floor.

The Velux could of course be unrelated, but it seems unlikely looking at it.

The seal doesn’t fail; what happens is that moist air is able to enter the gap through the tiny holes in the separator; it’s designed like that to deal with changes in atmospheric pressure. Every time the air pressure increases a few molecules of moisture enter then stay and eventually the moisture level reaches the point where condensation begins to appear. The DG unit is then said to have “blown”. It’s inevitable with time.

Wow, this is a new one on me. Have you got a link for this?

The seal doesn’t fail; what happens is that moist air is able to enter the gap through the tiny holes in the separator; it’s designed like that to deal with changes in atmospheric pressure.

No, the tiny holes are only on the inside and allow air to access the desilicate inside the aluminium spacer. There are no holes on the outside of the Al spacer, so no air can get in if the seal hasn’t failed. If you look at a DG unit, they normally paint the whole edge in a flexible glue like mastic, as a secondary seal to keep it completely air tight.

The pressure difference, from high to low atmospheric, is negligible and won’t stress the window in the slightest.

Failing a crack, the normal failure mode in a sealed unit is the mastic used to bond the glass to the spacer loses its flexibility and cracks and fresh air gets in; which eventually will wet out all the desilicate and then you will start to see condensation. A decent eg Velux sealed unit should be good for decades.

where did you read that globalti ? viz ?

the inert gas the units are filled with would escape.

the inert gas the units are filled with would escape.

only the posh ones (or at least it used to be), most cheap ones are/were just normal air…

I think the leak is further up, above the hinge anyway. You need to take off the covers around the top part of the window and check there. The screws are a possible source of water ingress. Put some mastic in the holes before you put the screws back. If you cure the leak just paint it to pretty it up and leave it as it is.

Send off a mail to Velux at Grothes in Fife, they will have a technical dept should tell you exactly has caused it and then just tell you do dig deep in your pocket and buy a new one to help pay for their new plush offices they are currently building

don’t know the technical terms so might be covered above but I’ve had velux leaking problems before..

first one, when you close the window do the ‘skirts’ of the grey metal window frame still sit the correct sides (both sides) of the ‘skirts’ on the frame in the roof?

second one (although not sure this properly explains it) is I wonder about the seal between the glass (itself) and the DG frame where you have that line of moss down the glass – I wonder if it’s possible the moss has breached the seal and is acting as a wick for the water to come in and make the wood damp – just to test it i’d strip out the moss, let it dry out, silicone seal it and see if that fixes it…

edit: reread, your profile seems ok (and is a better word than ‘skirt’) – second suggestion still stands, but I’d still silicone that end screw in case

Cheers folks..couple of things to try.

first one, when you close the window do the ‘skirts’ of the grey metal window frame still sit the correct sides (both sides) of the ‘skirts’ on the frame in the roof?

Don’t know. Do I have to sit on the roof to check? 😳😂

No, just take the window out. There are couple of buttons to press in then you can jiggle the window out. Tell us how many times you curse before you succeed.

What’s happened here is the build up of crap between the soakers and slates at the sides of the velux. You have to rake this crap out every so often because it dams the water which can cause it to climb over the top of the soakers. If you take off the lower side trims you will be able to look at the soakers; the soaker is an angled piece of aluminium the has the effect of extending each slate up the side of the velux. There needs to be one soaker under each slate, is this the case?
I would not fit the slates that tight against the sides of the velux as it will block with crap more easily.

Don’t know. Do I have to sit on the roof to check? 😳😂

i send my children up to check

and edukator’s right but again any children that are keen to help are useful here