COFFERED CEILING - Part 1

Coffered ceilings are one of those classic interior trim details that really standout.  On the surface they might look simple to construct - a series of box beams with crown molding wrapped around the interiors, but in reality they are much harder to execute well.    There have been a number of articles in the how-to and woodworking magazines on building these.  I read one in Fine Homebuilding a few months ago I think that, while an excellent design and method of construction,  it was not very efficient to build.

Fine Homebuilding, while still far better than most of it's peers on the shelves next to it, is a shell of what it once was, and is clearly more oriented toward the Home Depot crowd.  What was great about this magazine at one time was that they set the bar high and kept it there - something as a carpenter to strive for.  But, at the same time the projects featured for the most part were obviously done in a manner that one would have to to make a living doing them.  Half the projects featured now look like they were put together in a garage or warehouse just to take nice photos of them.    There was just some guy that wrote an article on clear finishing exterior stained doors - I think he put 15 or more coats of clear finish on each side, with a 24 hour dry time between re-coats - are you kidding?   Who has time or more importantly, money to pay someone for that?   I use a professional finisher that sprays a four or five fast drying coats of clear finish on an exterior door, leaving an incredibly durable, glass smooth finish.  He does it in a few hours and charges about $200.

Back to the ceiling - here is the finished product.

I built this last fall and the construction photos that follow are from this past weekend.  The houses were the same model and the rooms identical in size.   The rooms were 29'x17'.  We built a nine section ceiling with a three layer crown molding on the interiors of the panels.   Start to finish it took a crew of three of us, all professionals, about 22 hours to complete.  (66 total man hours).

To start - the usuals - set up a cutting area outside, but as close to the room as possible.  Stage your materials, move the furniture out of the room , cover the floor with tarps - taping them together and to the floor to hold up under the constant traffic.   Then layout out your grid.  You need to break out the calculators here and figure out your spacing and also determine the squareness of the room.  The latter is important as you need to keep your grid precise and square, otherwise you will have a nightmare installing the box beams and later the trim.  I layout the grid using in this case the 6" wide beams as the basis.  There is also a 6" bean around the perimeter of the room - you will see later that the way I build this allows you to "absorb" the out of square walls here, without being very noticeable.

Ceiling laid out - Installing cleats

We marked the ceiling along the long axis of the room first.  Use chalk lines for this as you need to be sure you have a precisely straight line.  Measuring off walls will not do as you can't rely on wall you didn't build or plaster.   For a finished space like this, use purple chalk.  Purple is the least permanent of all chalk colors.  I personally don't think anything higher than blue should be used in construction.  It drives me crazy seeing my fellow carpenters using red chalk all the time - this is pretty much permanent and will ruin finished surfaces.  If you need a permanent mark on say a floor that will receive traffic during work - use blue and then spray it with hair spray or varnish to "fix" it in place.  Once you have your longitudinal  lines, establish a right angle line using high school geometry - the  3,4,5 triangle.  In this case we used 12,16,20.  Mark your spacing along the line closest to a wall and measure 16' down in either direction.  With someone holding the end of the tape at the 16' mark and use it to draw an arc 20' away.  Then using the starting point measure out 12' and draw another arc - use the point that they intersect at to snap a line from the first point and you will have your 90 degree line - measure all the rest of the short lines off this.

Now that you have your grid, install your cleats.  Since the beams are 6"x6" - the cleats should be 4 1/2" wide - we used cut off from building the boxes (more on this later) and around the perimeter of the room, thin cleats, about 1 1/2", cut off from ripping down the horizontals for the flat part of the beams.  This conserves wood and uses up our scraps that normally would just be burned or thrown out.  We use construction adhesive, finish nails to hold the cleats in place, and then go back and screw everything in place with 2" drywall screws.  Always mark out the joists to nail and screw into - not just to secure everything, but also with all the modern systems hidden in walls like PEX piping and flexible gas lines, it's too easy to puncture something.

Building the boxes

With the cleats installed the outside man - the carpenter manning the saw and cutting all the components for the two carpenters inside who are installing them - builds the "boxes", using nails and yellow glue.  This is where things get a little ass-backwards from most of the coffered ceiling how-to articles.   While it's a style issue, I believe that the flat (horizontal) boards on the beams should be flush where they intersect.  You can't do this if you build beams and then lift them into place.  So we build nine boxes, install them, and then fit the horizontal piece between the boxes.  It's tricky and like I said earlier you have to be dead-on with your measurements and squareness for this to work out.

Start in the center

We again use finish nails to tack the boxes in place and then add 1 5/8" screws to secure the boxes to the cleats.  By the way the corner of the boxes are mitered - cut flat on a Makita 10" sliding compound miter saw.

Boxes up