While we are on the topic of caulk/sealant..
Control Room "inside out ceiling"I’m currently in the throes of installing the inside out ceiling modules – have completed 3 so far and am sharing my experiences here as I can’t find a lot of detail around how people have got comfortable with the sealing process.
The first one I installed in situ - dropping the Fyrchek sheets in from above and doing the backer rod/sealant from above. No option to do the “push up” method as the joists are not parallel in this spot as it’s where the flat ceiling changes to the rake so you can’t “push up”. I’m glad I only have to do one more of those.
The second was a “push up” module type. I have cleats across the top and a frame that holds the Fyrchek which I’m raising with my drywall lift.
(Straight out of “How to build an inside out ceiling” -
viewtopic.php?f=12&t=50.) The modules are light enough for me to then raise each end by hand from where the lift stops against the joists and hold it in place with some clamped blocks before securing the frame to the ceiling joists.
For me at least, the hardest part of this is getting the right amount and even spread of sealant to get a continuous seal. I want enough sealant to seal the gaps but not too much so that it ends up all over the joists as it gets lifted into place or more critically, that it ends up creating gaps due to unevenness in the sealant resulting from the “pushing in” process.
So for the 2nd one (first of the “push up” variety), I went with a clearance of 1mm between frame/Fyrchek and joist and 2 generous beads of sealant that I applied to the joist/cleats rather than to the module itself; 1 bead in the corner where the cleat meets the joist and the other around the joist at the height of the lowest sheet of Fyrchek.
Given the small clearance and volume of sealant, I was surprised to see no “bleed” of sealant from where the top of the module squeezes up against the cleats. This means that either I got it right or that there was too little sealant. Without superman vision, it is impossible to know. While I’m 99% confident that the seal will be solid in the frychek/joist join, to improve my confidence in the seal, I then sealed the cleat/frychek join working from above.
Never again – using a caulking gun in a 200mm (8”) space is not my idea of a good time – but I already knew from the unit I had to install in situ. I also sealed everything below
On the third (the second “push up” one), I went with the same clearance between frame/Fyrchek and joist and the same 2 generous beads of sealant applied to the joist/cleats.
But for this one I added another bead on the top of the fyrchek where it would hit the cleat - only I forgot to take a pic!
While thinking about how to fix the ceiling sheets under the silencer boxes, it occurred to me that the method I’d been using so far was a little bit overcooked for the weight of the Fyrchek I’m hanging, so I reverted to a more “traditional” approach of:
1. Fixing the cleats to the joists;
2. Screwing the first sheet of Fyrchek into the cleats – leaving a 5mm gap;
3. Pushing backer rod and sealant into the gaps;
4. Fixing the second sheet with some holding screws and temporary cleats for safety;
5. Pushing backer rod and sealant into the gaps; and
6. Attaching the frame (really acting as cleats) under the second sheet
No further sealant required.
This method is do-able in my situation given the weight of the sheets I’m hanging and this way I have 100% confidence in the sealing process filling the gaps. I’m not bagging/diss-ing the push up method – it is a clever solution when you have much larger modules but the “traditional” method works in my situation and takes half the time.
It will be interesting to see whether I can still use this method in the LR where the sheets will be 5% longer and 23% heavier (16mm vs 13mm) and I’ve got the green glue thing going on as well.
Just for completeness - a pic of the insulation - its easier to lay these in smaller blocks