Millie Master
Forum Member
No I didn't know that, however surely when it is painted then surely that overcomes this problem?Just one thing to bare in mind and I expect you already know, body filler absorbs water.
Bloody Stixall Ahhhhhhhhhhhhh
- Thread starter Millie Master
- Start date
SquirrellCook
Forum Member
As long as the paint seals it. I wonder if the flexible filler would be more durable for your application?
Millie Master
Forum Member
What flexible filler would you suggest is obviously the option, so what would you suggest?
mistericeman
Forum Member
I've often wondered whether 'some' applications call for a none setting mastic instead of a 'bonded' solution....
Think of applications where one side of the bond is rigid (roof light frame)
But the other side moves more (like a van roof)
Wind and harmonic vibrations can do some pretty odd things at times....
Possibly ending with the roof flex constantly trying to peel the bond apart....
Not always terribly difficult with a smooth/painted surface?
Dunno BUT It does seem like some situations folks really really seem to struggle to get a fully permanant solution.
Think of applications where one side of the bond is rigid (roof light frame)
But the other side moves more (like a van roof)
Wind and harmonic vibrations can do some pretty odd things at times....
Possibly ending with the roof flex constantly trying to peel the bond apart....
Not always terribly difficult with a smooth/painted surface?
Dunno BUT It does seem like some situations folks really really seem to struggle to get a fully permanant solution.
SquirrellCook
Forum Member
Flexible body filler is quite common, but it’s not so flexible as if you’d notice. Most car parts shop should stock it. It just damps panel flex.
SquirrellCook
Forum Member
I know it’s from an old boring post but it might give you some ideas.
Millie Master
Forum Member
Well I hadn't or rather didn't reveal this nugget yet, but on the central one of the rooflights, all the Stixall bonded sections, or rather the infill UPVC pieces I had filled the valleys with had stuck like sh-t to a blanket with no noticeable gaps, however I had bonded and then clamped the upper section/external part of the rooflight with a high grade mastic and it was very noticeable on taking the whole lot apart that it was sections of this mastic bond that had broken down and it looks like this was where most if not all of the water had gained access.
Coming from a flexi/flimsy caravan background, I can't even begin to think what had possessed me to use mastic in my build, I was simply following advice given on another (enormous) self building site.
Phil
mistericeman
Forum Member
I did use the term 'wondered'
Speaking from the view of folks involved in the plumbing scene....
Where they often fill/weight shower trays and baths to ensure the sealer bond is formed when the joint is at maximum negative deflection (full so at lowest point)
And under compression most of the time...
Hell... What do I know ;-)
Millie Master
Forum Member
There is nothing old or boring about your build posts
SquirrellCook
Forum Member
The mastic used on Murky‘s windows shrank to an extent you’d never believe it. I wondered why so much water came in.
Millie Master
Forum Member
I have worked on enough flimsy British built caravans over the years to know to never trust or use mastic and then like a total prat I go and use the blessed stuff!
I have now decided to do as my old mate Squiffy did, I will do a very thorough check of the roof, the bonding and the condition of the wood and if all appears to be OK I will then thoroughly clean everything up with spirit (it is Christmas after all) carefully position some masking tape and then quite literally flood the area with some more Stixall making certain that it is squashed into all the gaps as well as bonding down the top section of the roof panel on a goodly bed of it as well.
After all, as Squiffy said, the roof isn't under view and as long as it is 100% watertight.
I have also decided that from now on I will use the carefully fitted section of tarpaulin that I now have covering all 3 rooflights and the surrounding areas, very tightly secured whenever parked up at home. Doing this will have another advantage, namely it should stop the blessed seeds, catkins and leaves from my neighbours silver birch getting into the habitation area.
Phil
HarryInHudds
Forum Member
One issue I feel is important, which rarely gets mentioned, is the thickness of the layer of sealant.
We assume the joint is going to move, from thermal expansion if nothing else.
Non-setting Mastics absorb this by flowing (and hopefully back again). Cast in place elastomers (Stixall etc) flex; but they only flex up to a limit. If the joint moves, say by 0.25mm, and the layer flexing is 0.5mm, thats 50% stretch (or shear). If the sealant layer is 5mm thick then its only 5% stretch.
In my mind 5% stretch will be easy, 50% wont last very long.
Am I being too simplistic?
We assume the joint is going to move, from thermal expansion if nothing else.
Non-setting Mastics absorb this by flowing (and hopefully back again). Cast in place elastomers (Stixall etc) flex; but they only flex up to a limit. If the joint moves, say by 0.25mm, and the layer flexing is 0.5mm, thats 50% stretch (or shear). If the sealant layer is 5mm thick then its only 5% stretch.
In my mind 5% stretch will be easy, 50% wont last very long.
Am I being too simplistic?
SquirrellCook
Forum Member
That's the trouble with PU mastics/adhesives, it's very easy to squeeze to much. Window fitting mastic is much stiffer and has a grab tendency. Down side is it's black!
MarkJ
Forum Member
I used a non setting sealant, Dekaseal 8936, on my windows on someone's recommendation and it was great. It comes in various colours, not just black. I would have used it on the rooflights, but I had them 'professionally' fitted - the only thing I outsourced apart from the upholstery - and it didn't go well. They used a Sikaflex adhesive and swore profusely when they had to remove two of the rooflights and refit them.
Seems to me that's a benefit of a non setting sealant, so long as it does seal. If you think it's inevitable they're going to have to come out at some point then make life a bit easier. I don't know about other compounds, but the Dekaseal cured to an extremely sticky seal. I had to remove a window due to a Dometic manufacturing defect that required replacement and after about 3 months in-situ had it made a fantastically gluey seal, but one which you could break with some leverage. Then a simple clean-up with cloth wipes.
Derekoak
Forum Member
With my skylight 5 years ago. I cut out the roof and smoothed and painted the raw edge. I used butyl tape built up in layers. This is non setting. I bedded the skylight on the 20mm tape, leaving a little gap on the outside. Then as belt and braces. I went round the outside with a bead of black stixall into the gap. This hasn't leaked so far.