Club 80-90 Forums

What do you think causes the roofs to rust out on high tops, and is there anything that can be done to prevent it? my guess is that its condensation running down and collecting as has nowhere to go? would drilling a few holes on the inner skin help as would allow some ventilation.
Im asking as im goner to put a high top on my tin top.

Drilling holes won't do anything. You need to put a vapour control layer in. This is essentially a continuous layer of plastic running just behind the lining, and in front of (to the inner face of) the insulation and any support frame, and with the all the edges sealed between sections and to any openings. What this does is stop the moisture in the air inside the van, from cooking or people breathing out, getting in behind the insulation and condensing.

I cannot see how it gets in other than creeping under the gutter sealant. I have sealed the gutters completely with an L shaped plastic overlay over each gutter front to back. The L shaped plastic overlay butts up to the hi top side and effectively makes the gutters redundant with water shedding off the sides of the L shaped plastic.

I sprayed dinitrol S50 where the high top joins internally. Autohomes only bond to the roof down each side, the front and rear have rubber seals, removing these shows that at least over the fron and rear all is good.

On the rear seal where it meets the gutter line I have left a gap in each corner to enable any water that gets inside to run out.

I don't think there is much else I could do and, looking at the extent of the corrosion damage that can arise in our Hi Tops, the phrase "every little helps" comes to mind.

There may be a little that gets in through weak points in the sealant but the bulk will come from internal condensation collecting at the base of the high top trapped between it and the cut edge of the roof.

This problem has been discussed in various threads where hi top corrosion has been a problem. Condensation, failing gutter sealant/adhesive/fractures, osmosis, were all discussed as possible causes. Some owners have observed water sitting in the inside, and a lot of it, after periods of heavy rain fall when the vans are not in use. Whatever the cause, water seems to get in and, from my point of view, should be protected as you would a chassis and have some means of escape.

I've got a big interest in this because I've got the roof off our Westfalia Hightop to fix the rust and I don't want it coming back.
They definitely rot from the outside in but also from the inside out.
With a Westalia Hightop the weakest point is the way the roof is attached, with the edge of the fibreglass roof sandwiched between a folded strip of steel which is spot welded inside the gutters. This strip is installed with the roof and the gutter and the three sections are held together with the same spot welds. The paint top coat is on top of these layers, and between the bottom of the strip and the top of the gutter/roof surface is only a thin layer of primer. This means when the sealant in the gutters shrinks and hardens with age and moistiure creeps in it is attacking an almost totally unprotected gutter/roof/strip with predictable results.
When my roof goes back on I will glue the strips in with two pack adhesive and maybe just a tack weld at the ends of the strips, and plenty of epoxy primer covering these surfaces before the sealant goes in the gutter.
Van360.de have a page on their website showing how they fix hightops. They say a Hightop will still get wet inside and rust even when the outside is perfectly sealed.
They do lay some blame on the imperfect fixing of the hightop window, but say the biggest problem is condensation, quote in quaint Google Translate English: 'The factor condensing water is not to be underestimated, unbelievable what a person since so at night over the skin to the ambient air gives off moisture. One or the other makes a cup of coffee or cooks even small dishes in the VW bus. Again, water is in circulation. Have you ever camped in the winter? This shows extremely how the water flows out of the warm interior, heated eg by the auxiliary heating on the outer walls, the water escapes / condenses.'
A vapour barrier is maybe the only/best or one way to deal with this, but Van360 say: 'We get rid of the rust, bring in viaducts for water removal and conservation and you have no problem anymore.'
I'd really like to know how and where they create these amazingly effective 'viaducts' or I guess channels or simple drains that let any condensation drain out of the roof before it does terrible damage. At the corners maybe? By leaving gaps in the sealant or making holes somewhere? How would you do it?
Does anyone have any ideas how to create these viaducts?!

sweetaswesty wrote:I've got a big interest in this because I've got the roof off our Westfalia Hightop to fix the rust and I don't want it coming back.
They definitely rot from the outside in but also from the inside out.
With a Westalia Hightop the weakest point is the way the roof is attached, with the edge of the fibreglass roof sandwiched between a folded strip of steel which is spot welded inside the gutters. This strip is installed with the roof and the gutter and the three sections are held together with the same spot welds. The paint top coat is on top of these layers, and between the bottom of the strip and the top of the gutter/roof surface is only a thin layer of primer. This means when the sealant in the gutters shrinks and hardens with age and moistiure creeps in it is attacking an almost totally unprotected gutter/roof/strip with predictable results.
When my roof goes back on I will glue the strips in with two pack adhesive and maybe just a tack weld at the ends of the strips, and plenty of epoxy primer covering these surfaces before the sealant goes in the gutter.
Van360.de have a page on their website showing how they fix hightops. They say a Hightop will still get wet inside and rust even when the outside is perfectly sealed.
They do lay some blame on the imperfect fixing of the hightop window, but say the biggest problem is condensation, quote in quaint Google Translate English: 'The factor condensing water is not to be underestimated, unbelievable what a person since so at night over the skin to the ambient air gives off moisture. One or the other makes a cup of coffee or cooks even small dishes in the VW bus. Again, water is in circulation. Have you ever camped in the winter? This shows extremely how the water flows out of the warm interior, heated eg by the auxiliary heating on the outer walls, the water escapes / condenses.'
A vapour barrier is maybe the only/best or one way to deal with this, but Van360 say: 'We get rid of the rust, bring in viaducts for water removal and conservation and you have no problem anymore.'
I'd really like to know how and where they create these amazingly effective 'viaducts' or I guess channels or simple drains that let any condensation drain out of the roof before it does terrible damage. At the corners maybe? By leaving gaps in the sealant or making holes somewhere? How would you do it?
Does anyone have any ideas how to create these viaducts?!

yeah i defo think its condensation that is the problem, I also camp probably more in the winter as well so even worse. I was thinking of drilling a hole in each bottom corner of the inner skin of the fiberglass roof so that at least some air flow could get there to help dry out the condensation as i dont believe there is anyway to stop it getting there, you could never make the area 100% air tight to stop it. but im too interested what these viaducts are that van360.de take of

Ventilation is key - first and foremost. Granted you can't cut a hole in the high top but a proper vent will help. I have a tin top which also suffered from condensation (particularly when cooking inside on a wet day) but leaving front windows open by even half a centimetre will help maintain airflow and reduce reduce condensation massively.