Best Sealant for PVC Skylight integrated into Zinc Dormer?

Calibos

Best Sealant for PVC Skylight integrated into Zinc Dormer?



Built 8 years ago and have leaks on all 4 corners evidenced by water rings on the interior plasterboard ceiling. There was a single leak a few months after building that the builder came back and resealed but in the last year it seems to have sprung several more.

Need to DIY this myself this time. I've easy and safe access to the roof through a Velux and protected by a Valley between our roof and the roof next door.

Separate question but while I'm up there....... Any recommendations for a long lasting water retardant or wax/synthetic sealant for the Acrylic 'dome' on the skylight after I clean it, to prevent water spotting from rain and dust on the skylight for the longest amount of time?

5T3PH3N

Is that installed correctly?
Usually the flashing should come up to just below the the glass/clear plastic part on the frame.
You shouldn't be able to see much of white part.
That looks like the zinc installers did their part and then the dome was installed after.
The dome frame is supposed to be installed and then the zinc installers should have brought the zinc right up to the top of the white frame. There should be no upstand under the frame imo, the dome should have been put straight on to the flat roof.

Edit: like this- https://goo.gl/images/kY3FrJ
https://goo.gl/images/PUaZbb

Calibos

5T3PH3N wrote: »

Is that installed correctly?
Usually the flashing should come up to just below the the glass/clear plastic part on the frame.
You shouldn't be able to see much of white part.
That looks like the zinc installers did their part and then the dome was installed after.
The dome frame is supposed to be installed and then the zinc installers should have brought the zinc right up to the top of the white frame. There should be no upstand under the frame imo, the dome should have been put straight on to the flat roof.

Edit: like this- https://goo.gl/images/kY3FrJ
https://goo.gl/images/PUaZbb

Wouldn't surprise me as I always had a feeling myself that I'd never seen a rooflight like it before. Feckin Gob****e! Builder went bust soon after in 2010. Have since discovered one or two other things that were done wrong. For example the Attic conversion insulation under existing non permeable bitumen felt had no vent cards installed. Something I'll get around to rectifying myself eventually. Architect should have picked things like that up. He went bust too. Feckin waste of 18 grand for him. I didn't know as much then as I do now so didn't know any better. Theres other design choices that any architect should have suggested to us wrt stairs positioning etc but he literally let us customers dictate without making better suggestions. There were lots of other Shoulda, Coulda, Woulda's with this renovation.

Anyway, I digress. What sealer would you suggest I use to shore things up till I get a proper roofer up there to sort it out properly

5T3PH3N

Sorry to hear that, afaik Tec 7 roof will work on zinc and Tec 7 clear, which is called trans 7 will work on any skylight parts.

Bonzo Delaney

I'd agree with Stephen that the dome is badly fitted .
Personally I don't like the idea of using sealant as the primary defence on an exposed area.
Would it be possible to get a Zinc box shaped sleve made to the size of the curb that sits onthe roof but comes up under the under side of the dome that way it's a mechanical method of sealing the joint between the roof curb and skylight curb.
That way your covering the exposed white uPvc with matching colour roof zinc.

Calahonda52

National Seal in Western Ind Estate do a wide range of heavy duty "flash band type" tapes for such jobs.
I bought 15 meters of 200mm wide and 15 m of 70 mm wide there recently for about 70 lids.
The builder I bought it for heated it slightly with a hair dryer, as well as the wall he was putting it on and now swears but it, especially the adhesion.
I forget the name of it.... invoice is down the country, can get it next weekend iff you want, just PM me.

It can be cut to width.

I would flash it with this, starting at the zinc roof and work up with overlapping strips, using a seam roller to get it well stuck

https://www.woodies.ie/harris-taskmasters-wallpaper-seam-roller-1134910?utm_source=google_shopping&gclid=EAIaIQobChMIqLmK__yl2wIVhoKyCh2y2QvQEAQYASABEgKCuvD_BwE

http://www.nationalseal.ie

National Seal Systems Ltd
Unit 210, Holly Rd, Western Industrial Estate, Dublin 12
53.321856, -6.366395

Calibos

That photo in the OP was taken during the build when there was still Scaffolding in place for me to climb up there to take the photo.

Well, I finally did what I've wanted to do since we moved back in 8 years ago. I was troubleshooting an electric Velux over the landing and had to bring in a ladder to get up to it to press the reset switch on the window. After I'd had failed to find the problem with the electric velux I decided to try and remove the window and rest it in the roof valley. Turned out to be surprisingly easy. So I was able to get out onto the roof area, have a look around and take some new photo's of the Zinc Dormer and Skylight.

Turns out that after I took the initial photo in 2010 the foot of the skylight and also been clad with zinc. It still leaked though and the builder came back a few weeks after we moved in and used, as the photo's show, a white rubberised sealant. He really lathered it on almost completely painting the zinc cladding around the foot of the skylight. However you can see some spots where he didn't completely cover and thats how I know its zinc cladding over the foot instead of the bare PVC foot you see in the original photo above.

While I can't see any cracking in the sealant around the footing there are new leaks in those areas of the ceiling below on the corners and along the ceiling edge. However were there is cracking in the sealant and were there is a major leak a foot in from the skylight ceiling rim is at an overlapping zinc joint about a foot away from the skylight towards the main house roof apex. Although the zinc overlap is correct for the fall/slope of the dormer roof, a northerly or North Easterly or easterly would drive rain up under the overlap.

To me this actually looks like the Zinc Cladding contractors/installers fault. Like they ran out of zinc sheets long enough to run all the way to the skylight....or was it simply not possible because you need to end the crease folds before the skylight to allow water runoff to flow around the skylight and not pond up against the skylight???

Anyway, it looks like the builder might be off the hook for this one at least.

So now the question is whats the white rubber sealant the builder used. Do I need to peel of the existing failed sealant a rodo completely or do I just need to paint on some new sealant over the old??

or

Did I read something about being able to solder a Zinc roof?? Would that be a better option?

Also, do I need to worry about the moisture that got into the plywood and insulation underneath the zinc. Will that have dried out or rotted joists etc?







Sidenote:

Nextdoor neighbour always complaining about a leak in her boxroom wall caused by 'our' roof. After getting up there it turns out her entire roof drains into 'our' valley. She's a proper terrace on the other side but the front, side and back gutters of her house have no downpipes and all empty into 'our' valley shown in one of the photo's above!!

Calibos

Can anyone get back to me about the best way to proceed given that it now looks like the issue is with how the Zinc contractorrs fitted the zinc. It looks like water ingress is under the folded over seams very visible in the second last photo. The painted on rubberised sealant the builder added for the snag fix leaks has cracked and failed. In the photo in my first post taken just after the dormer was built and before the zinc was wrapped around the PVC footing of the Skylight you can see the shorter seam without the rubberised sealant.

So reseal with white product? Same as builder used? What is it can you guess? Do I need to strip the old off before applying the new? Should I instead strip off and solder?

Any further advice would be gratefully appreciated.

goz83

The old seal has failed so I would remove it. It will then give you a better idea of the problem you face. Being a Zinc roof, you should really get in a roofer to solve the problem. The Tec7 roof stuff is supposed to be good, but I don't know how well it would work on that roof.

Bonzo Delaney

That white sealer just looks cat on what should be a neat and expensive looking roof.
Try and remove it all from the zinc then as above engage a zinc installer to remedy it. Some one who knows what their doing and whose not going to pour a can of sealer over it.
If your going to put more of that gunk on it you might as well rip all the zinc off and fibreglass the roof area.

Calibos

Any idea what it might cost for a zinc installer to remedy something like this? That will determine whether I DIY stopgap remedy this with more sealant myself till I can afford the full and proper fix or if I can afford to get it properly fixed this Summer.

goz83

The price of repair is hard to know but it will cheaper than doing a DIY which will likely fail and allow more water in. Get a couple of quotes. It can’t be too expensive, as it’s a small area.

Def_IRL

That velux flat roof window should never have been used on a zinc roof. I know because I have the same one and Velux originally said it was OK for zinc, yet the upstand shape makes it very difficult to work zinc up around it. We finally made it work around 2 X of these Velux roof windows but it took the zinc lads two days of work just to do just zinc around those damm Velux upstands.
The upstand your builder built was more suitable let for a standard roof light window as per those you'd get from the likes of Vitral or Eos. But that upstand should have been a min of 150mm high, even for one of those Vitral or Eos rooflights.
It maybe easier to remove that velux, build up the upstand in wood to 150mm high, get a zinc guy out to re do the upstand, and then drop a Vitral/Eos kind of flat roof window in on top of that newly completed upstand. That velux as done will NEVER work as it's done, no matter
How many times you seal this bottom of its base, it needs to be sealed up into its own upstand.