Joint sealant

[samvoska]

Can anyone advise of a sealant for sealing the roof panel of a motorhome? The roof joint in question, between the cab and living area moldings across the width of the van, is held together by means of bolts at 2" intervals along its 7' length, but I need to re-seal the joint as I have a water leak. I guess I only need sealant rather than an adhesive, as the screws form the mechanical fixing? I have looked at the ScrewFix Direct website, who offer a multitude of sealant products, that seamingly offer everything I need i.e. strong, flexible, weatherproof and UV resistant, but all this product choice is baffling. So I'd be most grateful if anyone could sugest a tried & tested product. I would normally book the van in at a repairer, but they all seem to be fully booked into July, so I'd like to be able to fix the van, to get some use out of it now. Many thanks in advance.

[Clive]

I found by asking at a large caravan outlet with a big workshop that their workshops don,t use any of the various mastics and sealants that the outlet shop sold. The workshop foreman was quite direct about what was best and that is what he eventually sold me, as used in his workshop. I cannot remember its name but suggest you visit a well known emporium close to you and ask the workshop guys the same question. When you re seal then remove the complete length of the aluminium extrusion and thoroughly clean all surfaces both sides of this and the overlapping roof sheets first. (Petrol normally works) Get a box of new stainless steel screws from Screwfix or wherever to replace the removed screws with. And NO SMOKING ! Good luck Clive

[Derek Uzzell]

Samvoska: It would have been helpful to know the make/model of your motorhome, as there might then have been a sporting chance of knowing what sealants the manufacturer used in the first place. The types of 'DIY' products sold through caravan outlets and builders' suppliers are unlikely to be suitable for the task you are planning. I suggest you seek advice from specialist sealant producers and you could try either of the following websites: www.sika.com www.loctite.com/int_henkel/loctite_uk I've found both companies very helpful when I've sought information in the past.

[samvoska]

Many thanks for both replies, the motorhome is a 2002 Rapido 985M A-Class.

[vaila2]

Sikaflex is the stuff to use, comes in black, white, or grey, though you might have to look in a chandlers rather than a DIY place.

[Derek Uzzell]

There are more than 20 adhesives/sealants produced by SIKA Ltd under the brand-name "SIKAFLEX". The most commonly available is likely to be SIKAFLEX-512 CARAVAN but that's in white only. Difficult to know which product Vaila2 is referring to as several SIKAFLEX sealants are coloured black, white or grey. If you tell SIKA what you want to do they should be able to tell you which of their products would be most suitable. I don't know what sealant Rapido uses, but I've seen SIKA products in French DIY stores and, when I was looking for shower-compartment sealant for my Hobby, a French caravan dealer suggested I contact SIKA. You could ask the UK Rapido agents to find out from the factory what they use, then you could be sure of a colour match.

[Simon]

I`ve always used Sikaflex products in the past. However the last product I used was an adhesive sealer by Wurth. I used it to fix a former on the roof of the Murvi before drilling a 48mm hole through it for a Status ariel. There was no movement of the former at all.

[tezza]

Samvoska I used to have the old Autohomes Highwayman, so i have a lot of experiance of useing sealants, the one that I always used to great effect was a product called Carafax Caraseal IDL99. I bought this from my local caravan dealer, it cost me 3 years ago £3.99 a tube. If I quote what is on the tube it says, " non hardening mastic, giving constant adhesion and flexibility". Uses " used for seams, joints, rails and mouldings in caravans boats, containers and road transport vehicles, also for bedding of window frames and cladding panels". The tube is white with red writing, the colour of the mastic is cream. If you can't get it, the address is; Careafax Ltd. Rotterdam Rd. Sutton Fields Ind. Estate, Hull. Tel. 01482825941 I hope this helps you. Tezza

[Rowan Lee]

John Wickersham's article "Go, Stick or Bust" on page 215 of MMM in June 2005 is an absolute revelation. A must read for anyone about to purchase sealant.

[Mel E]

If there is likely to be any movement between sealed surfaces - for example, if one is metal and the other plastic, then the sun's heat will cause differential expansion - then you MUST ge4t a flexible sealant.

[Guest peter]

I have used carafax on my boat which leaked for years. Brilliant stuff, no more leaks as it never sets and can move. Sticks like the proverbial to a blanket. You can clean off any excess with white spirit.

[docted]

I liked the title of this thread. Personally I always licked the paper! Good luck Docted

[samvoska]

Many thanks to all, I'll check out all recommendations and let you know the outcome. Thanks again.

[samvoska]

Nice one Docted, it tock me a while bu Ive got it now ; )

[enodreven]

Hi, I would have thought that a good quality external Silicon would work i have used it for sealing the screws etc when i fitted the secuity locks and i feel sure it will provide a sealed joint against any water ingress ??

[Derek Uzzell]

Samvoska: If you are planning to DIY fix your leaking roof-joint permanently then I still think the sensible thing to do before going ahead would be to consult Rapido on what sealant they use. However, if you just want to waterproof the leaking area of the joint temporarily until a professional repair can be carried out, then Enodreven's suggestion has merit (with perhaps a length of duct-tape stuck over the offending area to provide extra protection). A few days ago I mentioned your problem to a motorhome dealer. We both believed that the roof-to-cab joint on a 9-Series was structural and that Rapido would have employed a modern high-strength adhesive/sealant to supplement the attachment-bolts holding roof- and cab-sections together. Such joints, if properly made initially, are normally 'for life' and it's concerning that the one on your 985M has failed. The dealer suggested that, to be certain of curing the fault permanently, it might be necessary to remake the joint completely (ie. by unbolting the two sections, removing all existing sealant, introducing new sealant and re-tightening the bolts). Obviously the severity of the water ingress and where it is getting through the joint will dictate the remedial treatment required. One thing's for sure, for a successful permanent fix that won't harm your motorhome's appearance you need to use a product that's suitable for the task and, because the joint is visible, the correct colour. Silicone sealant has minimal structural strength and relatively poor adhesion. Although fine for small sealing jobs, it would be inappropriate for a transverse 7'-long roof-joint fully exposed to weather and movement. Caraseal IDL99 is a bedding mastic - essentially a sticky non-skinning goo - OK for sealing unseen non-structural joints that may need to be pulled apart later, but not intended for what you are planning. There is a variety of jointing products on the market that combine through-curing (no sticky outer surface), high adhesion, strength, flexibility and UV resistance. Henkel, Wurth and SIKA products have already been mentioned, but there are others. In fact the dealer I spoke to told me that he had now moved away from the often-recommended SIKA 512 CARAVAN to another manufacturer's sealant (I forget which) that worked equally well but had a much longer shelf-life than SIKA 512 once the sealant cartridge had been opened.