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Coffered Ceiling incorporating trusses

Coffered Ceiling incorporating trusses

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Old 12-11-17, 02:56 PM
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Coffered Ceiling incorporating trusses

Hello All,

I am trying to solve a low ceiling problem (7 1/2 feet and it drives my wife nuts) and had the idea make roughly 24" coffers incorporating the trusses and putting there drywall on top rather than below the bottom chord and running 2x4 pieces cross-ways between the trusses to create coffers to essentially gain 4" and add some visual interest.

Not considering the work and whether it would be worth the gain, is there a structural reason why this is a stupid idea. My online searches have yielded no results on an idea like this and I figure there has to be a reason as I don't think it is that creative an idea. I am pretty good at pulling off complicated DIY projects as long as I have ample sources to research to ensure I do the job right. With this one, I just can't find the info. I've looked into what it takes to create a tray with the existing trusses and while it seems perfectly possible, even with an engineer being involved, I don't feel comfortable bracing and cutting the trusses.

Thanks for reading. I appreciate your feedback!
 
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Old 12-11-17, 03:10 PM
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Makes 0 since to me, wait for other posters.
 
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Old 12-11-17, 03:13 PM
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I was struggling with finding a way to explain it that I thought made sense. I'll see if anyone else is on my wavelength before revising, I suppose. Thanks.
 
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Old 12-11-17, 03:35 PM
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I don't feel comfortable bracing and cutting the trusses.
Well, you never cut a truss, (if that is really what you have) so right there your idea is out the window. If you can do it without cutting (essentially making a 22 1/2" x 22 1/2" gridwork... assuming they are 24" on center) it would be fine, but a lot of work. (If they are 16" on center, i also think that would nix your plan) Coffered (tray) ceilings usually need to be symmetrical and your truss layout will not be symmetrical right to left in relation to the walls. You could hide that by leaving a large flat area next to the walls.

Trusses also have quite a bit of movement as they expand and contract, so if this is going to be painted, it would probably be a caulking nightmare every time the seasons change. Building a coffeed ceiling under the trusses is one thing... incorporating them INTO the trusses adds a whole 'nother dimension of movement that would be hard to predict.

And you would need to completely reinsulate this area once you are done.
 
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Old 12-11-17, 05:39 PM
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Thank you XSleeper!

Yes I absolutely will not cut trusses (and yes they are trusses, 24" on center). Incorporating trusses into the grid work was exactly what I was thinking so it sounds like you are following my thinking. 22 1/2 x 22 1/2 or so is exactly what I was thinking and the spacing of the trusses in the room in question does actually allow symmetry. Its a 16 foot room right to left and I am able to start the coffers 2 feet in from each wall. Its an open layout and I am only thinking about the living room area so I have flexibility in spacing going forward to back. That was one of the first things I checked and thought that was pretty lucky.

I also assumed I'd want to air seal the top with foam board insulation, sealing with expanding foam around the truss webs, taping seams, and so forth, and then put the blown in insulation back over that. The movement part is tricky, though. We weren't planning on painting it but I wonder if the movement would still some undesirable things like break air seals with the foam seams. Thanks so much for the helpful feedback!
 
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Old 12-11-17, 06:14 PM
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A good way to do it would be to put 2x2 cleats on the trusses, maybe 8" up... then hang 1/2" drywall on that. Foam could lay between or on top of the cleats. Any voids between the cleats and drywall edges (inside your truss webbing) would need to be draft stopped and fireblocked so that it is air tight.

To trim, make yourself up a bunch of premade boxes... such as 1x8's with outside measurements of maybe 22 1/4 x 22 1/4... inside measurements of 20 3/4 x 20 3/4. Shim them in place, use 4 finish nails per side to attach them. You would probably want to use a laser to ensure you get all the boxes perfectly aligned, because your truses may not be perfectly straight. (For example, I would use a PLS 180.) Adding 22 1/2" long blocking above your trim would at least help keep everything spaced correctly.

Once all your trim boxes are installed, cap all the bottom edges of those boxes that are parallel to the trusses with 2 1/2" wide 1x trim. Then fill in the other edges with short pieces of 2 1/2" wide 1x trim, cut to fit between the others.

Put your crown moulding together like a picture frame... (2" or 3"crown would probably look good) it will be put together like a box that is 20 11/16 x 20 11/16. Nail all your miters together from the back side of the miter.

Then slip that crown moulding assembly up into the box until it's tight against the drywall lid and pop a couple nails in the bottom edge on each side to hold it.

If you intend to stain and varnish the trim, prefinish all the trim so that you just have to fill nail holes and then give it one last coat of finish after its installed. No caulking anywhere might be the best way to go about it.

Your outside perimeter (the flat drywall ceiling) could be finished with a corner bead, and your 2 1/2" wide trim caps could fit between, butting up to the corner bead on each side. It might work well if your boxes were 1" above the drywall perimeter (flush with the bottom edge of the framing) so that the 2 1/2" trim would appear slightly recessed where it mwets the drywall perimeter. (1/4") this might mean double rocking the ceiling perimeter so that the drywall perimeter at least 1" thick.
 
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