Coffered Ceiling Beam Materials

      MDF is straight, stable, and uniform, but Poplar is lighter. September 23, 2008

We recently signed a contract for the trim package for a rather large banquet hall. The job will include roughly 500 ln ft of coffering. After researching various designs on the web, my question concerns the underlying box beam in the coffer design, before application of the crown and mouldings. Does anyone have any advice on what material to construct this base "beam" from?

The design is calling for 3/4" solid material on the two sides and bottom of the "beam". The sides will be attached to cleats secured to the ceiling. The design is roughly 15' x 15', so ideally I'd like to use 16' lengths to minimize joints. I've considered 1x poplar, 3/4" primed MDF, 5/8" MDF or 1/2" birch ply for the box beam. Anyone have a suggestion?

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
I have always done mine with 2 x 4 then the "boxes" with pine, oak or whatever material is spec'd. I attach to 2x with screws and glue it high enough to be covered with the following crown molding. The finished width of the boxes will dictate the width of the rough material.

From contributor L:
Youre asking about the beam itself, and not the mounting material "underneath" the beam holding it to the ceiling, right? If it's getting painted, and unless there is a good or required reason to use real wood (like it will be "distressed" before or after installation), MDF is the way to go. It's dimensionally stable, holds a good detailed edge and paints out well. You might get someone to fingerjoint two 8' rips into your 16' pieces, but a scarf joint made on site would work well since most coffered ceilings are high up and finished dark. If it needs be real wood, use poplar. For the mounting blocking, Ive found rips of 1" (or 1.125" subfloor material) plywood to work well. If you need more thickness, double it up. 2x6" dimensional lumber could twist on you and make it a struggle to get the beam installed.

From contributor V:
How big are the beams? You can get primed MDF up to 1x12 in 16' lengths, so that's an easy method (if heavy). I'm thinking plywood would be most difficult because you'd need to have some joints. Depending on your layout, that might not be a problem though. Last, but not least, poplar would be a great way to go - it's just the more expensive option (Poplar ply = $1 +/- per square foot, MDF about $.60, Poplar around $2.2).

From contributor G:
If you look at the picture as a whole then poplar will probably be cheaper. The extra labor that you are going to introduce to make each one of the seams seem like they aren't there will probably offset the cost of the solid stock rather quickly. You only have to lift one pc and you won't have to have to deal with the seam at all. Going from MDF to poplar will cost you about $9 each. In my world that is about 9 minutes worth of time. If it will save you that much time you'll break even and it'll make the job easier. If it saves you more then you will profit by doing it this way. Figure out your own pricing, I just did it off the top of my head and didn't calculate it out.

From the original questioner:
Thanks to all who offered assistance. We'll be going with the 1x poplar for the box beam. I was leaning toward MDF but was hesitant due to the weight. We'll be preassembling the "beam" on the floor and then lifting it into place. Just felt that the poplar would be more rigid than the MDF and not flop around as much. All the other mouldings will be MDF. Once again, thanks everyone for your opinions.

From contributor M:
In the future if you want to use MDF try the "ultralite" its less than half the weight of regular.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor I:
I've just completed a large coffered ceiling project (14x14) using poplar and it worked quite well. I considered MDF but ruled it out not only for weight reasons, but the challenges of finishing MDF edges based on my design. I considered finger jointed pine, however the yards in my area are all carrying paulownia as their FJP offering and while it's a great product that's nice and straight I was concerned the beams might droop/sag in the middle since the product had quite a bit of flexibility. The edges were also slightly rounded, not as crisp as the poplar, and had uneven primer buildup and bleed through. I did use the FJP equivalent for the cleats and it worked just fine. The poplar pained up nicely with a good sprayed oil finish after filling the nail holes with famowood.

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