Ducato roof - fixing water drainage issues.

[fred_jb]

I have a Fiat Ducato based PVC which has a wide skylight at the front and and an aircon at the back which I installed in place of the original rear skylight. As a result the channels in the corrugated roof between those two things are blocked at both ends and cannot drain. They then fill up with stagnant water and muck, and encourage the growth of algae, especially while enduring a UK winter. I am also concerned that long term this may well encourage corrosion of the roof. I have recently decided to rejig stuff on the roof the allow me to fit a second 200W solar panel, matching the original main panel, in place of the current second panel which is only 80W. As part of this I decided to do something about the water draining problem, and thought it might be of interest and would like to hear people's views on whether what I have done is sensible.

The reason I couldn't fit a larger second solar panel originally was that the bathroom skylight and the TV aerial were in the way, so as part of this job I replaced the bathroom skylight with a lower profile one which has the bonus of a fan and additional interior LED lights, though had to be modified slightly to avoid fouling the shower curtain track. This will end up under the new panel so will not open fully, but will be able to be wound up as far as the underside of the new panel giving enough of an opening for the fan to work as I have made up some taller mounts to raise the panels. I removed the large ugly TV aerial which we hardly ever use and replaced it with a waterproof connection box containing a TV aerial socket. This will allow us to deploy a magnetic stick aerial on the roof on the rare occasions we want to pick up broadcast channels - we mainly use streaming stuff for entertainment. I also move my Starlink roof mount and treated it to a magnetic mounting frame.

What I decided to do was fill the channels so that the slight curve of the roof allows water the drain off the centre section to the unblocked channels either side. I couldn't find any material which fitted exactly but found some plastic architrave material 65mm wide and 6mm thick which was bevelled on one side and fitted pretty well when glued upside down in the grooves with a layer of flashing tape underneath to raise it slightly. This was then overlaid by some 100mm wide by 2mm thick PVC cover strip stuck down with Sikaflex. The whole lot was then painted with special fibre reinforced acrylic roof paint. If we get a couple of dry days before I need to put the panels on the roof I might put a second coat on but it is probably not needed. Some pictures below.

The more or less finished job:

New bathroom fan:

Filling the grooves:

Raised solar panel mounts:

Changed to white Sikaflex for the last part - the black stuff seems to get everywhere!

Acrylic paint:

 

[royandsharont]

Can’t say I’ve noticed water standing on the roof of mine causing stagnant pooling and I see it every fourtnight in winter and less frequently in summer

 

[fred_jb]

Can’t say I’ve noticed water standing on the roof of mine causing stagnant pooling and I see it every fourtnight in winter and less frequently in summer

Maybe you don't have roof furniture that blocks some of the grooves at both ends?

 

[stevewagner]

Nice job!

 

[Kannon Fodda]

Yes my van has rooflights that block the grooves at each end so there can be standing water, and eventually if I don't clean (which happens especially over winter), some gunge can accumulate. But more worried that the mastic to rooflights remains intact than standing water.

Big concern with your blocking stuff is if your seals start to fail could water be trapped under your fittings and you have no idea until much too late?

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[fred_jb]

Yes my van has rooflights that block the grooves at each end so there can be standing water, and eventually if I don't clean (which happens especially over winter), some gunge can accumulate. But more worried that the mastic to rooflights remains intact than standing water.

Big concern with your blocking stuff is if your seals start to fail could water be trapped under your fittings and you have no idea until much too late?

Yes, I was mindful of the possibility of water getting underneath. I was initially just going to fill the grooves and then paint over it, but when I started doing that I wasn't convinced that the paint would fully fill the gaps. That is why I added another layer with the perimeter of every plastic plank carefully sealed with Sikaflex. I hope that, plus probably a second coat of roof paint over the whole thing will ensure there is no water ingress. Also of course, pretty much all of this area will be covered by the solar panels so will be shielded from driving rain.

The other concern I have is that flexing of the roof might break the seal. I have had no evidence of that on the existing roof furniture, and the acrylic paint seems to retain some flexibility, but I will keep an eye on it.

 

[royandsharont]

Maybe you don't have roof furniture that blocks some of the grooves at both ends?

Yes I do. A very large roof light at the front almost the full width of the van. A raised solar down one half then a much smaller central roof light at the rear.