The architect Christopher Alexander wrote “totalitarian, machine buildings do not require trim because they are precise enough to do without. But they buy their precision at a dreadful price: by killing the possibility of freedom in the building plan.” (Incidentally, Alexander’s Pattern Language is a fascinating book on design. This link is to his “Pattern 240″ on “half-inch trim.”) While I don’t see trim in ideological terms, the stuff is a vexing challenge in modern residential design.
For concreteness, let’s consider trim to be the aesthetic feature at the boundary between windows and walls. In the most common instance, trim is wood surrounding doors and windows and laid flat against the drywall. Of course many other situations are possible (e.g., brick, tile, metal, etc.).
There are two very good reasons for trim. First, it allows the placement of the doors and windows to float a bit relative to the rough opening in the framing, and it allows the drywall to be installed with relatively low precision. Trim can suck up as much as 2-3 inches of imprecision in those tasks. Hanging drywall is done with only slightly more precision than excavating a ditch with a backhoe. (If a loved one is thinking of quitting school, have them watch a drywall crew for a couple of hours….that is a very tough way to make a living.) The second reason for trim is aesthetic. Trim emphasizes transitions, highlights openings in the walls, and can itself have nice material qualities when, for example, it comprises a carefully finished piece of wood with an attractive grain.
In modernist residential styles, four approaches to trim are common:
- No trim, with just a drywall “return” (corner) terminating at the window jamb.
- Porthole trim, which is essentially an extension of the window jamb 1/2″ – 1″ past the wall.
- Flush flat trim, usually with a little gap between the trim and the wall.
- Flat trim applied on top of the wall surface, the common approach.
Here are some illustrations and commentary.
No trim with the drywall return makes a lot of sense for a very thick wall, say 10″ or greater. When you have to cover a lot of area, drywall is a good approach. It is fussy for the drywall crew to get this approach right, but probably less expensive than buying, installing, and finishing trim. I find the look a bit stark. Ironically, although often a feature of high-end modernist homes, the “no trim” approach is also an economy tract-house strategy in much of the U.S. Usually, a sill of some kind is used on a trim-less window because drywall sills are not very durable from drips, wiping, dust, etc. — particularly at lower heights.
The porthole approach looks nice in my opinion. It gives some framing to the window opening, but is clean and simple. In theory it is quite affordable because it doesn’t use much material. It also allows the windows to be ordered with no jamb extensions, which saves a few bucks. The main disadvantage is that it really requires the drywall crew to come back after the trim carpentry and fill in the gap between the rough edge of the drywall and the protruding edge of the trim. This filled area then has to be sanded and finished/painted. Again, drywall folks work fairly cheap, so this isn’t that big a deal. My plan is to spray paint the entire interior before installing the trim, though, and so I’d be filling, sanding, and then repainting those gaps. Probably not too big a deal. Indeed, it’s not too big a deal to paint after trim has been installed. The porthole windows are easy to mask, so spraying remains possible. I also worry somewhat about the plaster pulling away from the wood. My guess is that over time, cracks open up between the wood and the plaster.
The flush flat trim really requires a tidy little gap between the trim and the wall. This is a fussy, expensive drywall detail. It also never quite looks right to me, especially as it ages. I think this detail is quite nice in theory, but in implementation it doesn’t quite live up to the promise. I really don’t think the flush trim is nicer on balance than the protruding flat trim, and so never really considered this approach. (Incidentally, sometimes this little gap is applied to the porthole approach as well. The same concerns apply in that case.)
The least expensive, most conventional approach is trim applied flat over the wall. Every finish carpenter knows how to do this. It can be done before or after painting. In my opinion a narrow square edged piece of flat trim gives a nice modern look and is an honest, economical strategy. Thus, I’m going with this approach.
I considered several different materials: clear vertical grain (CVG) douglas fir, clear alder, clear vertical grain antique heart pine, and weathered gray barnboard. My family didn’t like the barnboard. I find the fir a bit too soft. The antique heart pine is drop-dead gorgeous as wood, but I can’t afford to have the doors made in this material, and so I’m worried about getting a harmonious trim/door combination with this material. The clear alder is clean and simple…boring really, but I’m not sure that drawing attention to the trim is a good idea anyway. Mostly I want it to just manage transitions gracefully without being obtrusive.
In these mock-ups I was also experimenting with a 1 inch offset on the top piece and with exposed fasteners. (These screws are mostly natural steel combi-drive screws from McFeely’s…if you’re into screws, these are mighty fine.)
My plan is to use a simple, square-edge flat casing 3/4 – 7/8 thick (whatever the most economical stock turns out to be) by 2 1/4 inches wide. I played around with different widths and this is what looks nicest to me. Currently my plan is to use clear alder with a clear finish (most likely just Minwax wipe-on polyurethane, or possibly buying the trim stock pre-finished). I’ve decided to go with conventional finish nailing (power nail with the trim nailer and fill the hole) and a flush-aligned square edge.
Here’s a photo of the mock-up of that material, size, and alignment.
Update as of October 2010…
I ended up using clear, vertical-grain fir for the casing to match the fir doors I wanted to use. I decided to miter the corners instead of using a square edge. Here is the casing going in.