[demonical]

Hey all,
I don't have any specific questions, but figured I'd chronicle my coffered ceiling build. In a previous thread I discussed my ventures into airless painting of a room I'm turning into a large formal dining room.
https://www.diychatroom.com/f4/new-airless-spraying-couple-questions-682879/
I've loved the look of the white coffered ceilings here in some of the New England coastal homes and have taken it on as my next project. I chose the Gary Katz style, who is a finish carpenter that's laid out online his style of building coffered ceilings. His articles online were helpful, along with a couple of the discussion threads on JLC. I bought his DVD series for my own knowledge about finish carpentry and partly to support him, but the DVD's don't really covered the coffered ceiling topics. I also picked up a used copy of his book, which has a small section on coffered ceilings. Even after reading everything I could, there were still a couple questions I had about my own project, which he was kind enough to answer and suggest the ceiling layout I ended up choosing.


PDF of article here if interested:

https://www.google.com/url?sa=t&rct...Ceilings.pdf&usg=AOvVaw1BOmc_ma02kGh3WAwMIrhi

The room is 17 ft by 20 ft. I'm adding a chandelier in the center of the ceiling, so I wanted the layout to allow for the cells to align so that one is in the center of the room. I'm also going to use 4x8ft paneling in the cells on the ceiling, so I wanted the cells to be no larger than 4ft on the smaller dimension. He suggested what he called a marginal layout, meaning the cells are slightly inset from the walls. So I'm going with a 3 x 3 layout, but inset 18 inches from the walls, so the perimeter will be partial cells.

Working alone, and not being a professional who's done this before, it's certainly turning out to be time consuming but things are still going smoothly. I planned out the beam sizing and measurements to allow for the whole ceiling to be made from the same lumber, so I chose 1x6 finish grade pine. I'm using the same pine for the hollow backings.

I did the layout in Sketchup. Then I measured to find the center of the room, and measured going out from the center to snap the chalk lines. The chalk lines are for laying out the hollow backings, which are 5.5" in width, whereas the full beam width is 7".

 

[demonical]

The previous owners of the house had left this marble slab piece in the garage, so I've taken advantage of it as a flat smooth surface for constructing the hollow backings. After snapping the chalk lines, I used the laser just to keep track of joists so I could screw backings into joists in addition to the 15g nails and construction adhesive.

 

[demonical]

The bottom beams are definitely more time consuming when working alone. Even having a 3rd arm would have made things easier. Any unions are done with 1/4" spline joints. For the splines I first tried 1/4" thick MDF, but the locally available 1/4" MDF has a true thickness of 0.22" which I at first thought would be fine but given the lengths of the boards there was still too much play. So I grabbed a 1/4" x 3.5" poplar board and cut it into small strips to use as splines which gave a tighter joint.

 

[ron45]

You're kidding right.?
Seems like a waste of time and effort and not very stable/sound.

https://www.familyhandyman.com/carpentry/ceiling-panels-how-to-install-a-beam-and-panel-ceiling/

 

[demonical]

Of course much of this is a learning experience, but I've done the calculations, and seen a good number of professional installers online do the same style of hollow backing brackets or cleats. Maybe I'm off somewhere?

The design uses 375 feet of white pine, 0.75in thick by 5.5in wide. At a density of 28 pounds per cubic foot, that's a total weight of 300 pounds for all of the ceiling beam work. The 16 T brackets are screwed into the joists with GRK #10 framing screws, PL400, and butterflied 15g nails. 12 more of the remaining brackets are nailed into joists. Even if we assumed the 16 T brackets are doing most of the holding, that's 300 pounds distributed between 16 brackets screwed into the joists, 19 pounds of weight per bracket. Or 11 pounds per bracket if you include all of the joist attached ones. On top of that, any of the beams that meet the wall where there's a joist are also nailed into the wall joists. The 300 pound beam work is across a 340 square foot ceiling, creating a bottom dead load of less than 1psf.

 

[ron45]

Of course much of this is a learning experience, but I've done the calculations, and seen a good number of professional installers online do the same style of hollow backing brackets or cleats. Maybe I'm off somewhere?

The design uses 375 feet of white pine, 0.75in thick by 5.5in wide. At a density of 28 pounds per cubic foot, that's a total weight of 300 pounds for all of the ceiling beam work. The 16 T brackets are screwed into the joists with GRK #10 framing screws, PL400, and butterflied 15g nails. 12 more of the remaining brackets are nailed into joists. Even if we assumed the 16 T brackets are doing most of the holding, that's 300 pounds distributed between 16 brackets screwed into the joists, 19 pounds of weight per bracket. Or 11 pounds per bracket if you include all of the joist attached ones. On top of that, any of the beams that meet the wall where there's a joist are also nailed into the wall joists. The 300 pound beam work is across a 340 square foot ceiling, creating a bottom dead load of less than 1psf.

Now do the math on the one I showed you.

Then compare the nailing surfaces to the ceiling, compare the strength.
Compare the amount of tools needed.
The amount of material/different material
Then compare the time schedules.
Then compare the price.

 

[carpdad]

Sorry didn't read the whole post. Your system seems to follow modular construction using main frames that connect with brackets. It, however, focuses on the brackets. I wouldn't do it with brackets first then fit the frames to them sort of way. It feels too factory made and too many uncertainties for field mistakes. Also agree with ron45 that the whole ceiling structure (and weight) may be on the brackets and few screws into the joists found every 16" or so. Screws eventually could work themselves loose from the joists above. Then gaps will open. I would prefer less pieces and more fasteners.

 

[Dave Sal]

I have been following this guys videos. He makes everything seem so easy. Here's his technique on coffered ceilings.