Sealing around roof vents

Discussion in 'Motorhome Chat' started by Hymie835, Oct 10, 2014.

  1. Hymie835

    Hymie835 Read Only Funster

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    Hi all
    I need to replace sealant around roof vents and Heiki before leaks start, as I can see sealant cracking and drying. I wondered what dealers do in this case and what diy'ers do. Obviously the best thing to do is remove entire vent and rebed the sealant. A very large job.

    I would not have thought dealers do this on annual basis. Do they just caulk around the vents as you would a shower tray???

    Motorhome is a Hymer A class, B544 1999 (and it is brilliant!)
     
  2. outkast

    outkast Read Only Funster

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    if you are going to use anything use silicone.
     
  3. dippingatoe

    dippingatoe Read Only Funster

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    This is what the professionals do.... doesn't always work very well though!
     

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  4. outkast

    outkast Read Only Funster

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    that's not what the professionals do, I apply sealant and mastic of all types for a living and have done so for the last twenty years, what you see in those pics is the result of someone attempting something they are clearly not qualified to do.
     
  5. iandsm

    iandsm Funster

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    No its not all what professionals do, if they are any good that is. What a particularly unhelpful reply that was.

    In any case to answer the question. Total removal of the roof light and associated sealer followed by re sealing with the proper non drying mastic (On a roll and from caravan accessory shops or ebay) is the only way to ensure the thing won't leak and provide peace of mind. Removal is not difficult and whatever roof light you have it will only be held in place by screws from the underneath inside. Remove any trim and the screws then gently push up from inside or prize up from outside. An old wooden peg separated will be a good tool to remove the old sealant as would an old credit card or similar. Don't sweat, its a fairly simple job and well within the skills of even a modest diy,er. Do NOT use sikaflex or anything that sets permanently.
     
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  6. Moodybrook

    Moodybrook Funster

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    Thought the non drying mastic would be in a tube ?? can you recommend a particular make ??
     
  7. jonandshell

    jonandshell Funster

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    The only way to do it properly is to remove the vent and refit it CORRECTLY- unlike some manufacturers!
    Putting another bead upon bead upon bead to try and fix a leak will just make a mess and not be effective.
    There are plenty of semi setting sealants and tapes that will do the business.
    DO NOT USE SILICONE! It will be hammered by UV and split and peel away in no time.
     
  8. Hymie835

    Hymie835 Read Only Funster

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    Thanks all for replies, I think iandsm has the answer. Remove completely and rebed.

    I do wonder what some dealers would do though......which is why I am doing it myself!
     
    Last edited: Oct 10, 2014
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  9. OllieUK

    OllieUK Read Only Funster

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    On my mobile grooming van I had a skylight that needed resealing and I dreaded the thought of doing it myself. I tried all sorts of stuff to seal it such as creeping crack, Tiger seal, and gaffer tape. then it got so bad I had no alternative.
    I had the vent resealed at a dealership 2 years previous and they charged me over £100 to do the job. It took 2 men 4 hours to complete the work.

    I bought 1 tube sikaflex off ebay. I unscrewed the 8 screws around the vent from the inside of the van, and removed the vent. Then on the outside you need to clear all the old sealant from the opening, this takes time but its worth it to get a good seal when you restore the vent.
    Clean all the old sealant from the skylight.
    When your satisfied with your work run a bead of sikaflex around the opening where the vent sits, position the vent makeing sure you have applied enough sealant. From inside the van insert all the screws, at this point I also put sealant into the holes before the screws. I finished off with a bead of tape.
    You will be suprised how easy it is. I was and wondered why it had cost so much at the garage. It took me from start to finish 1.5 hours.
     
  10. scotjimland

    scotjimland Funster Life Member

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    Non-drying bedding sealant, from most caravan dealers or Google it

    Caraflax IDL 99
     
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  11. iandsm

    iandsm Funster

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    Hymie 835, Whatever yo do, DO NOT use sikaflex. Its and excellent adhesive and thats the problem. For example, if you ever had to remove the roof light, perhaps because you missed a bit and needed to repeat the process, to the roof light became damaged in some way and needed replacement, you would NOT be able to remove the roof light without breaking it and then removing the sikaflex would be a nightmare, very very difficult indeed.
     
  12. OllieUK

    OllieUK Read Only Funster

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    I really don' t agree with this statement. Sikaflex 512 is an elastic sealant which bonds well with a wide variety of products. The purpose of the post was to offer advice on how to stop a leaky skylight Sikaflex applied correctly will do just that.
    The removal of any pre bonded application should be done with care not to cause any damage, removal of old adhesive is the time consuming hard part.
    Remove cured Sikaflex by scraping the product with a razor blade or a putty knife. cleansing agents will not work.
     
  13. iandsm

    iandsm Funster

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    Then Hymie 835 can take his choice. The correct bedding mastic or semi permanent Sikaflex. I don't suggest Sikaflex is not great product, or that it would not stop a leak, its certainly better than gaffer tape but it is just not the best option for this purpose. given the extreme difficulty of removing it from things attached with it or any surface. It can only be removed mechanically by being cut,scraped or ground. Some have suggested a cheese wire to cut through it, thats fine if you can get access to it, you still have a devil of a job to get it off both surfaces. Thats why motorhome manufacturers do not use it to fix/seal roof lights .Just google Sika.com and read the data sheet.
     
    Last edited: Oct 10, 2014
  14. Jim

    Jim Ringleader

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    We used to carry a 70kg of canoes on our motorhome roof. The weight of them and me and the roof tieing them on and getting them off made the roof flex a lot, especially the Heki. Always used Sikaflex, to seal and reseal. 221 I think but maybe 521, did a great job.
     
  15. outkast

    outkast Read Only Funster

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    the correct silicone, applied in the correct way will do the job perfectly, preparation is the key, take it apart and make sure all mating surfaces are free from any residue of the current sealant, one of the best ways to make sure of this is to scrape off as much as you can and then wipe the surfaces over some of those builders wipes, best ones I found to do the job are gorilla wipes, you can get them from places like B&Q, get a good silicone, no offence to sika but there products are not the best on the market, go to a diy store and look at the range available, dow corning are good, you want one wich has a good elasticity, it will tell you on the side of the tube, and one wich has good resistance to UV rays, once you have made sure both surfaces are totally free of any residue, dust or poisture, apply to both surfaces providing a bed of silicone, push down on the vent so the silicone ozzes out of the side a bit, it should ooze out all the way round, now get one of those little bottles they sell at garden centres and put some water in it with a little washing up liquid, spray around the joint, this is to stop any silicone being smeared when you do the next bit, best for this is an empty silicone tube, scrape around the joint removing the access silicone with the open end, this will remove the silicone into the open end of the tube, the spray again and lightly run you finger around the joint.

    once again preparation is the key, if I go to a job where any form of mastic, silicone, polysulphide ect has broken down, 9 time out of ten it because someone has prepared the the joint properly.
     
  16. Peter_n_Margaret

    Peter_n_Margaret Read Only Funster

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    My view is that silicone is great for gutters and house bathrooms but should be banned from motorhomes. Once an area is contaminated with silicone, it is extremely difficult to remove and nothing else will be effective.
    I use Sikaflex Pro which is a long life sealer, not an adhesive.
     
  17. gillnphil

    gillnphil Funster

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    I did my roof vent 3 moths ago. I used Sikaflex sealant, it stays elastic and does not go hard. It worked a treat and the hardest bit is scraping off old sealant. Easy job for a reasonable DIY er
    Phil
     
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