Sealing Roof Leak with Fibreglass

[Al68]

I don't have a self build though I have done quite a bit of rebuilding of the coachwork after getting leaks at roof level in my CI Carioaca 644.
Working from inside I replaced the rotten wood and replaced internal panel with plywood. I resealed the junction between the aluminium roof skin and the side frame. The joint aluminium moulding was bedded and screwed down. I also resealed the junction between the aluminium roof sling and the front overact fibreglass moulding. I used Sikaflex and proprietary none setting sealant to achieve this. I thought I had solved the problem, however, I have signs of damp on the nearside just behind the passenger door of the Fiat Ducato cab door.
A long time ago I built a sailing dinghy using the stitch and glue system to join panels in the hull. I am thinking that I could do similar with resin and tape on these roof joints. I don't intend to fibreglass the whole roof - yet!

Has anybody done similar?

 

[DavidG58]

My daughter impulsively bought a leaker a couple of years ago

we paid for new roof lights , hopefully removing where we felt the greatest risk of leak was

like you it didn’t , following guidance on here we then investigated ‘aluminium cancer’, took a section of roof lining down (had it done, beyond my skill set) there were dozens of pin holes in the roof

the motorhome was relatively cheap, we painted the roof with a fibre impregnated substance, didn’t look pretty in gun metal grey, not sure if other colours were available , but it seemed to stop the obvious leaks

it might be a simpler solution for your joints maybe , applied by paintbrush , we did the whole roof, 2 coats in a day

 

[funflair]

Firstly I am wondering how the manufacturer sealed the roof joint? Other than badly.

A couple of things come to mind re fibreglass, standard polyester resin will eat polystyrene insulation so any resting creeping into the joint will melt the insulation which looks like polystyrene in your photos, the other worry I might have is that there could be movement between roof and wall when the van twists and a fibreglass tape joint might be too rigid.

If it was me I would be tempted to use something more flexible like Eternabond tape after securing the roof/wall junction.

 

[Al68]

It's a 2005 model and so perhaps 10 years is the life of sealants on CI quality motorhomes. I can't see any evidence of failure in the roof lights though.

Yes, the rigidity issue had crossed my mind. If it bonds to the aluminium roof skin and maybe folds over the wall panel but is not bonded to it there would be a degree of freedom. I would then bed the existing rubber gasket on Puraflex mastic and screw the finishing trim over the top has in the original construction.

I don't know but the problem may be the joint between the aluminium roof sheet and the overact fibreglass moulding. It does form a dam and after rain, water is always seen to lie there.

It's too cold and wet to work outside yet and so I will keep researching. I know some resins are more flexible than others but which.

 

[sweetie]

Could you not remove roof lights and side roof trims and get sheet of butyl pond liner and cover entire roof then fix roof side trims with a bed of mastic underneath and screw down, and seal over screw heads. Cut holes for roof lights and again bed on mastic.
I know this is different but I have done similar to pitched shed roof and thinking of replacing upc roof of conservatory with ply then cover with butyl.
I think some American RV,s have a butyl roof.

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[68c]

Use two part liquid EPDM rubber, designed for RV roofs and us just painted on.

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[Al68]

Thanks for the large scale ideas but I am still thinking of local discreet solutions.

 

[Jamesh]

I would use a polymer based sealant / adhesive like ebt or 5200m or simalar.

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It will seal that corner and an Alu cover piece in one go.

Cheers James

 

[TheBig1]

Tanking paint is the cheapest and quickest solution. The paint includes rubber fibres and is used to seal swimming pools and ponds etc. Available in a whole raft of colours and has been used to great effect by members on here dealing with porous aluminium roofs on motorhomes