Advice on sealing roof window

[H F]

The previous owners built a conservatory with two roof windows. The sealing is a complete dog’s dinner. They’ve used flashing and with all the rain we’re worried about water ingress leading to leaks.

 

We are wondering how to best seal these windows once the lead has been removed. It’s likely to be a spring/summer job but would like to plan for it now.

 

suggestions and advice, as always, is welcome.

[ProDave]

I would not give that the satisfaction of being described as a "roof window"  It look like some DIY bodge job.

 

What's the roof material?  it looks like box profile sheets cut into strips?

 

The lead flashing above the window needs to be longer and tuck under the roof cladding strip above it, not end just below it with half a tube of some sealant hoping to seal it.

 

And the same with the side flashings, they need to be longer so they tuck under the roof sheet above.

[H F]

It’s a horror story isn’t it? Glad you agree,

 

The roof surface is called Plastisol - it’s a sheer metal that can be used for roofs.

 

Would you recommend replacing the lead with something else? Not sure lead flashing was the right option here.

[Ferdinand]

"Plastisol" is actually a plastic pvc coating applied to sheet roofing to protect it further over a normal galvanised coating from water ingress. It can also be used to give colour. 

 

See:

https://www.cladco.co.uk/choice-of-coatings

 

I have a sunlounge roof done in plastisol coated box section corrugated with a roof angle of about 6 degrees. 6 years on, no problems. No windows in it, however.

 

To me there do not look to be enough fixings in the pic - though light by only perhaps a third, which may be OK.

 

What to do?

 

If you are not currrently getting leaks I would leave it until probably May (ie when the dry season starts), and have thought about possible solutions before then. If you are getting leaks I would jury-rig until the weather is less waterfall-like.

 

Corrugated is good at keeping water from tracking sideways, and I think your issues will be water up the roof coming in the top edge,  and water on the window running under the seal. 

As to a permanent solution? Perhaps see if there is a kit from somewhere the right size which would fit, or make the window a bit bigger and make it proud of the roof service. I would try and avoid wholesale roof replacement, but otoh corrugate dis tricky to cut.

 

Ferdinand

 

Edited December 20, 2019 by Ferdinand

[H F]

We tried to see this off until the summer. Not that lucky. We’ve sprung a leak - I think the black stuff is mastic but it seems to have degraded. Does it degrade over time?

 

Any solutions?

 

During a dry spell, should we rip this stuff out, clean it, and replace it? If yes, what would be recommended? Mastic, silicone?

 

Really fed up with other people’s shitty workmanship. 

[ProDave]

Before you can address the problem, you need to know where the water is getting in.

 

Initially I thought it was the poor detail at the top where the top flashing is not correctly tucked under the sheet above.

 

Are you now thinking it is getting in at the edge of the glass and there has been a previous attempt to re seal it there?

[Cpd]

How much money do you want to chuck at it..... by the time you strip out the lead and find a bunch of rotten wood to strip out..... and then realise that as it’s just a double glazed unit bodged in from the start your going to have to Heath Robinson the thing again as you can’t actually buy a flashing kit for it........  how about a nice new Velux with a propper flashing kit and you end up with a window that will open when you want and will last a very long time.  Go crazy and redo that lovely .... fake tile tin while your at it  and put in a few extra windows........   just an option to consider........l 

[Dreadnaught]

I don't know if this will be much help, but I have just ordered my rooflights for my forthcoming build and here are the cross-sections and installation instructions for them. I might give you some insight and thoughts about your own rooflight problems: https://roof-maker.co.uk/rooflights/flat-rooflights/fixed-flat-rooflights/

Edited February 16, 2020 by Dreadnaught

[H F]

36 minutes ago, ProDave said:

Before you can address the problem, you need to know where the water is getting in.

 

Initially I thought it was the poor detail at the top where the top flashing is not correctly tucked under the sheet above.

 

Are you now thinking it is getting in at the edge of the glass and there has been a previous attempt to re seal it there?

It’s getting through the top. I just took the photo from the bottom to show the mastic.

 

Maybe it needs to be tucked in better.

Edited February 16, 2020 by Home Farm

[H F]

21 minutes ago, Cpd said:

How much money do you want to chuck at it..... by the time you strip out the lead and find a bunch of rotten wood to strip out..... and then realise that as it’s just a double glazed unit bodged in from the start your going to have to Heath Robinson the thing again as you can’t actually buy a flashing kit for it........  how about a nice new Velux with a propper flashing kit and you end up with a window that will open when you want and will last a very long time.  Go crazy and redo that lovely .... fake tile tin while your at it  and put in a few extra windows........   just an option to consider........l 

We have considered that. The other massive issue is that the existing windows are a custom, stupid size... so we can’t like for like change it. 
 

We might have to do that in the summer though... just need a fix for the next few months.

[H F]

22 minutes ago, Dreadnaught said:

I don't know if this will be much help, but I have just ordered my rooflights for my forthcoming build and here are the cross-sections and installation instructions for them. I might give you some insight and thoughts about your own rooflight problems: https://roof-maker.co.uk/rooflights/flat-rooflights/fixed-flat-rooflights/

Thanks for that. It might cast some insights.

[H F]

If we were to remove the lead, what else could be used to keep the water out going forward? 
 

I guess my question is, how do professional gutters fit custom windows that don’t come with kits.

 

 

[ProDave]

On 20/12/2019 at 12:40, Home Farm said:

This is the problem imho.  That lead at the top should be much longer and tuck UNDER the roof sheet above the window.  At the moment at best it buts up to the joint between the roof sheets and has a tube of sealant trying to stop water getting under the lead.

 

So start with replacing that with a larger strip of leas that really tucks under the roof sheet above the window.

 

Because the rest of the window is also a bit dubious, I would try and form a bit of an upstand in the leadwork so instead of allowing water down onto the glass, it encouraged it to run off the sides above the window and down the roofing sheets

 

While you are at it, the lad down the sides should be wider so they at least lap down into the first valley of the roofing sheets. At the moment water on that flat section can blow under the lead.

[Jeremy Harris]

There's also a potential problem with using lead above a window, as the glass will end up being stained by the lead salts that wash out over time.  As a general rule it's best to try and arrange things so that there isn't much possibility of water running off lead flashing on to glass.

[Vijay]

no idea if it would stick to glass, but maybe contact the manufacturer - but if you masked nice straight finished edges, could you use something like Acrypol?

[Roundtuit]

If you want a short-term fix with a view to doing a proper job later, I'd Flashband it to death. A bit of heat from a hot air paint stripping gun and it sticks to most things!

[Cpd]

5 minutes ago, Roundtuit said:

If you want a short-term fix with a view to doing a proper job later, I'd Flashband it to death. A bit of heat from a hot air paint stripping gun and it sticks to most things!

‘yes I would try to avoid using any lead as it’s gets very expensive very quickly, I like the idea of either doing it well or spending as little as possible and not worry what it looks like as long as it’s waterproof. If flashband or another product will stick to the roof and glass then possibly strip the lead off, clean it all up and do a good temporary fix with some flash band or equivalent.