This is my fist post on here after a lot of lurking in the background! Having finally bought my first van and now finding a bit of damp!! i'm after a bit of guidance please. Hope i'm posting this in the right place!
Am in the early stages of a reseal (with the help of some great guides on here, thankyou) and have hit a bit of a stumbling block.
Can anyone recommend the correct width/thickness of roll mastic to use to reseal my van?
I'm beginning with the rear rail first and that measures 25mm wide. Do i try and get mastic as close to or just under that width or do i get something slightly narrower. I was also planning of running a bead of silkaflex along each side once ive put it on?
There seems to be quite a few different widths and thicknesses available. Can you recommend a decent brand and a place to purchase the right stuff.
Roll mastic is convenient but deteriorates over time. Sikaflex doesn't. If you clean both faces well, mask the 'van and degrease with plenty of meths before applying a thorough dose of Sikaflex (then cleaning up with white spirit before it sets), you will never have to touch the rail again. I would dip each screw thread in Sikaflex too.
If it has to come off again use roll or other non setting mastic. If you want it to be sealed forever use Sikaflex but make the job perfect!
On a 25mm awning rail, use 19mm mastic roll which leaves 3mm each side for a bead of sikaflex. W4 mastic is a good brand and widely available on the net (fleabay)
just doing the same myself. use 19mm tape and run non setting mastic along rail as well. Then clean off mastic that squeezes out with paraffin. A good point here , as i found out too late, is that when screwing rail back on use a slightly longer screw say 5 to 10 mm. The reason is that when you put the tape on its about 3mm thick and the screws on my one didnt bite as well when i was screwing it back on .Best of luck. PS another tip was to put masking tape along van in line wth rail so when you take it off you can see where it goes back to, also any mastic coming out will go onto tape , making cleaning easier. Just dont leave it on if it rains cos it appears to set like concrete.....
I`d use white silicon bathroom sealer mesel . . . be OK for a few years . . .easy to apply and reseal. But what do I know?? Trial and error isn`t the best principle is it?
------------- Peripheral people don`t have as much excitement but they sure live longer
White silicon bathroom sealer would last until there was a frost - or it was very hot in the sun - not a good adhesive.
Strip mastic is possibly what the rails were originally put on with. Why would it be any more water resistant or long lasting 2nd time around?
Paraffin and Diesel are pretty good solvents and penetrating solutions, you could use them to clean up excess mastic - but then why would you want either anywhere near a join that shouldn't be penetrated?
This is 2012. Why insist on 1950's sealant technology?
Because its cheaper, its easier and it is why there are so many leaky caravans around.
Sorry if that made no sense, before doing the awning rail i removed a screw and then got new ones, 3 x 20 mm. But when i applied tape to the seam on the van, then put mastic onto rail, i found that because of the thickness of tape and mastic the screws wouldnt tighten back up very well. I then got 30.mm screws, which dont go too far through and they gave a much tighter hold when screwed in. Hope this helps. Dont use silicone because a caravan joints do move so thats why you need to use a non setting caravan sealent. I use paraffin when cleaning has thats what my local caaravan repair place uses, does the job very well. But each to their own.
hi use same width as rail then hopefully u dont need to silicon both sides of rail.as u screw rail tite the mastic should protrude out and wet ya finger with soapy water and smooth down into rail