Resealing roof joint - help required re: methodology and mystery of different sides having different arrangements...

[Sibsbibs]

Hello all,

I’m hoping you can help. We’ve just shelled out a small fortune to have a damp repair done, the entry point (and telltale discolouration) being hidden on the inside under the overcab bed fascia and fixing, which might be why the NCC approved technician didn’t pick it up on his pre purchase check and report. You live and learn... Anyway, although the inside rotten section has been replaced, the joint wasn't resealed by the garage at the same time as we needed to collect it for our holiday - the internal repair having taken up all the available time pre-holiday. The garage put a bit of sealant along one suspect section just to get us through the holiday, but it now needs to be removed and rebedded properly.

I’ve re-bedded sealing joints on our old caravans, so am happy to take on the job myself, but one end of the sealing strip is different to the other. I don’t know which is the ‘correct’ joint, so am attaching photos. You’ll see the left hand side has an extra strip of something or other that loops over the side wall/roof junction, whereas the other side doesn’t (in case you’re wondering, the damp problem was both sides, so no clues there...).

I’m guessing the side with the extra bit is how it would have originally been, but that’s just a guess. I’m not sure what this substance is - it’s hard to the touch but moulds tightly around the wall/roof junction. I have no idea what to use to emulate this. Any ideas??

For the main plastic strip, I was going to follow the approach I’ve used before (which I think I pinched from John Wickersham) and bed the strip on a non-setting mastic ribbon (the stuff that comes on a roll) then run a bead of sikaflex 512 along either side and smooth to finish off. But really don’t know what to do about these odd side bits.

Any/all help and suggestions would be hugely welcome.

Thanks a lot.

 

[Terry]

Hi what ever you do don't use mastic on a roll ...Use Puraflex 40(from Toolstation) for sealing or sticking anything,ideal for what you require Used on my selfbuilds for last 10 years or so Sikaflex 512 will work but after a year or so it let's go on lots of plastics Mastic on a roll always leaks ....never had anything leak with the Puraflex

 

[Sibsbibs]

That’s interesting, Terry - I’ve never heard of Puraflex before, but it looks like it’s an Everebuild product, which seems to be part of Sika (or vice versa). I wonder why Sikaflex 512 from the Sika stable is considered the usual sealant for caravans/motorhome if Puraflex is the superior product?

 

[Terry]

Yes part of the Sika group but Puraflex sticks like in my first post over the years I have tried lots of different sealents and about 20 years ago I spoke with a old caravan maker who told me Sikaflex let go on some plastics so I did a few test sticks on various plastics (used to have my own plastic window business) so had plenty to try things on.I knew that at the time everyone used Dow Corning, and although it stuck that also let go.After speaking to reps etc we found out that you needed to use Natural cure Dow and not the High mod that everyone sold you.(vinegar smell)
Over the years I have tried lots of different sealents, hence Puraflex 40. If you want a grab adhesive then the best I have found is Grip and grab by Siromer but once you press it on it's not coming off

 

[Sibsbibs]

Thanks a lot Terry - thats a useful insight. We’ve got a Toolstation locally, so I’ll look further into Puraflex. Any suggestions about what to use along the side bits where one side has some sort of moulded strip going over the wall-roof joint, but the other side doesn’t?

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[Sibsbibs]

Sorry Terry - one more question - do you use any of the Sika/Everbuild primers to promote adhesion before use? I recall John Wickersham recommended a final clean up with pure meths to make sure any white spirit residue used for cleaning surfaces is removed and doesn‘t compromise the bond. Any suggestions for best approach?
Thanks again

 

[Sibsbibs]

And one more - what minimum thickness would you advise? One reason for using mastic on a roll is that it takes the guesswork out of getting the right thickness, but prepared to give Puraflex a go if I can get the application right...

Thanks again!

 

[Terry]

Hi I use uPVC frame cleaner (solvent) on most things.Use masking tape on both sides and smooth off with a wet finger then remove the tapes while it's still wet. Depending on the gapi usually let the Puraflex overlap by approx 2 mm each side .Use the solvent cleaner with paper towel,it will clean off any excess Puraflex off after you pull the tape but be careful.If you smooth it off nicely you should not get excess If bedding a rooflight down I draw around it and mask off a 2 mm strip/ tape and apply a good pencil thick bead ,press down, smooth off and remove tape After a bit of practice it becomes second nature
Edit ask away

 

[Sibsbibs]

Brilliant - thanks a lot, Terry. Just so that I understand right, am I also looking for approx 2mm depth of Puraflex underneath the trim, once I’ve pressed down? And any ideas what to do about the side bits? I just can’t fathom what was used on the side that has something moulded over the wall/roof joint, so can’t begin to guess what to look for to emulate. I could just build up a mound of Puraflex I guess and neaten as best I can, but whatever’s already there is rigid but slightly sculpted, as if it was pliable when applied, then hardened.

Thanks very much

 

[Terry]

Hi Sibs, if you have pvc widows have a look at sealent on the sides to give you an idea You can get plastic trims from 20 mm to 90 mm wide , I would suggest 28 mm D mould ...got to go will explain later

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[Terry]

Hi again 28 mm D mould can be placed on top to bridge a gap,simply apply a bead of Puraflex , press the d mould down onto it then seal the sides (2mm ish)
See if there is a eurocell place near you they sell all the different moulds in 5 MTR lengths ,,,,28 mm D will be about £4 ,they will wrap it into a circle so it fits into your car

 

[Sibsbibs]

Hi Terry, I had a look at Eurocell‘s D mould and, if I’m looking at the right thing, is that the kind of strip you get as trim around a pvc window? I’m wondering if that would be anywhere near flexible enough as there‘s a really marked tight curve to the profile. A bit like wrapping it round half an egg. Will that work? Thanks for the tip on getting it in the car. Could have been tricky...

 

[Terry]

Not sure on the bend but you can get a small grinder and cut slots (probably 5mm apart)across the underside without going through the top to help it around tighter Bends ( called kerfing in joinery ) I have 1mm cutting discs perfect for the job

 

[Sibsbibs]

Oh blimey, Terry, now that’s technical... I think I can do that, but don’t trust myself with anything sharper than my junior hacksaw or I’ll go right through... Will take my time and get hubby to keep the tea coming - can‘t trust him with a steak knife, let alone anything resembling a tool...

That’s wonderful. I now have a method, Eurocell is a mere 5 miles away and I see they also stock solvent pvc cleaner - thanks so much for all the tips.

 

[Terry]

Don't use a jnr hacksaw but use a big one and cut small v shapes out ,,,, after you have cut a couple out try bending it you will soon get the idea,,, more Vs better the bend

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[PeteH]

I've got a product which is used in the caravan industry, given to me by a line manager it's not branded, but I suspect it is made by Bartoline at Beverley . Christ does it stick!. And after 3 Years it`s still flexible too.

 

[Sibsbibs]

Thanks so much Pete and Terry - I’m picking up my Eurocell and Toolstation orders tomorrow and hoping there are enough gaps between the thunderstorms to get the job done this W/E...

 

[Ingwe]

Interesting and useful thread. Thanks all.

 

[The Wino]

I can't claim any expertise but would use some flat strip over the half an egg bit then d profile mitred at the ends butting up to it. In cutting out v sections there are in effect lots of joins anyway in the edge nearest the roof I would sooner just have two and it would look nearer.

 

[Terry]

I can't claim any expertise but would use some flat strip over the half an egg bit then d profile mitred at the ends butting up to it. In cutting out v sections there are in effect lots of joins anyway in the edge nearest the roof I would sooner just have two and it would look nearer.

The v sections only allow it to bend it continues to be one piece and the v's are filled by the Puraflex you bed it on and seal the sides after bedding The D section only has small pencil rounds on each side so at 28 mm wide is in effect a flat piece only about 4 mm high. You can also get some Bay flexy strip about 140 X 2 mm which is very flexible but you would have to rip it down to say 25m wide and if you don't have right power saw its very easy for it to snap off especially trying to cut 5 MTR lengths
Edit each to Thier own You can buy 1.5 mm Ali flat bar which will bend very easy but would require painting

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[Sibsbibs]

Hi Terry - Eurocell were only showing a D profile at 25mm wide with a depth of 6mm, so banking on the 3mm difference to what you suggested making not too much difference. The greater thickness seemed immaterial if I’m doing v cuts every 0.5 cm as you suggest - I just cut a little deeper I guess? I did wonder about a plastic bendy strip too, but wondered if it would provide a robust enough covering to be worth much more than just piling up a mound of Puraflex over the curvy bit of the join?
But re-reading your latest post, Terry, I now see that you’re suggesting I replace the current plastic strip with the Eurocell strip in its entirety, doing away with the need for a joint between the existing (rebedded) strip and the bits that need to go on each side. Is that right? So I effectively end up with one long bit across the width of the entire van, having ‘kerfed’ each end to mould round the curvy bits? In which case I’m definitely going to want to use the more robust D strip from Eurocell, aren’t I?

it’s tipping down here anyway, so no rush to get weaving...

 

[Terry]

Hi Sibs if you can get the flexy strip in a width you require that will be good and it will not require Kerfing It does not require to be strong as it's only a cover strip. If you are struggling with the plastic try Ali flat bar but it will require paint. I personally go for plastic because I have tools required and once fitted requires no maintenance. If you can get away with a join just keep an eye on it

 

[Sibsbibs]

Thanks a lot Terry - I used aluminium bars on joins on my conservatory, painting them white to match. Never again - despite priming and painting with good quality metal paint, they still flaked with 18 months, undermining the bead of sealant I’d run each side - don’t want that happening on the motorhome too... I’ve ordered the Eurocell stuff, so will press on with Kerfing - and look at plan B only if I make a hash of it...

 

[Terry]

Sounds like a plan .....look at buying a cheap grinder the blade it comes with will do the kerfing bit

 

[Sibsbibs]

Hi again,

well I’ve been up in the drizzle to see how easy it is to pry off the old strip - not at all, so may have to get out the bread knife or something. Anyway, more concerning is the possibility it might be sensible to do another job before rebedding this strip, because the curvy side bits will cover the beginning of the roof/wall run which I suspect will need attention in the not too distant future given the age of the old boy (2002 Eura Mobil), so seems crazy to re-bed the front strip only to have to unearth it to update the sealant along the roof/side-wall junction before long. It seems to come in sections, so only need to do the front section initially, but I’ve attached photos of the assembly.

Unlike in my caravan days, where there was a simple metal rail attached with screws and sealant, this all looks a bit different. The cover strip I’m pointing to lifts up to reveal a series of screws and, judging by the look of the roof junction, there appears to be a rubber gasket of some sort, out of which, in patches, there‘s the black gunky stuff Eura Mobil seem to squirt everywhere.

I’m not terribly sure what’s going on without starting to disassemble the whole lot, but wondering - if there’s a rubber gasket and some sort of application of gunk, is that normal? And am I likely to unearth a gasket that looks like it needs replacing, meaning a potential delay while something is ordered from Eura Mobil (if it doesn’t look replicable elsewhere)? Any ideas, before I open Pandora’s box? Which might have to wait a bit longer as I only have this weekend clear to do anything before I’m due to take him to Scotland at the end of the month, unless we go crazy and fly to Italy if their virus rates stay low and typical Scottish weather is forecast...

thanks yet again

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[Sibsbibs]

... and, no, we haven’t washed the roof of the old boy yet this year - he would have got a wash and brush if he hadn’t spent an extended stay at the garage being patched up...

 

[Sibsbibs]

Sorry - one more thing - any opinions on how safe it is to weight bear on the roof. I’m not monstrous - a shade over 8 stone - but suspect you’ll tell me I need to check with Eura Mobil, who’ll probably say no. It’s just going to be much easier to get to the central bit if I can crawl over the roof a bit - carefully...

 

[Terry]

Hi get rid of the knife use a paper scraper or a Sharpe plastic wedge and use the frame cleaner to clean muck off. I would mask it off about 5mm wide and simply reseal/ Puraflex , smooth off with wet finger and remove masking tape ....yep it will take your weight if worried use a thin sheet of plywood .

 

[Jamesh]

I don't think you need v cuts a single cut perhaps 2mm deep every 2" any fewer and you will get straight - kink - straight.

If it won't take the bend cut 1mm deeper. Perhaps try a test piece first.

Cheers James

 

[Sibsbibs]

Hi there - yes, I found on a test piece that v cuts weren’t necessary - the cut itself was enough to allow for bend - the D strip has a decent amount of flexibility in it which helps. But I think I might keep the side bits separate so that I can reseal the main strip and add the side bits at the same time I reseal the roof/wall joint at the front. Any clues about how the roof/side wall joint is put together to give me an idea of what’s involved in removing and re-sealing? The rubber gasket carries on the entire length of each side of the roof and down along the rear panel, but there’s no sign of the gungy black stuff at the rear - and it only appears in patchy lengths along the roof section - not all of it - so not quite sure where/why it would have been originally applied? I’m more used to caravan resealing, so not sure what‘s normal for this vintage of motorhome? If there is a normal...?

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