I was in a bathroom recently, taking in the door and window casings, wall paneling, and some skylight and rafter details. The trim boards on the skylight didn’t fully meet the edge of the rafters. The wall boards had gaps. And the window trim wasn’t flush with the edge of the window casing. But this was all intentional.
I’ve never said it out loud, but for some reason, in my head, I’ve always called this carpentry detail intentional offset. I think I stole the phrase from nautical navigation. I never gave much thought to how it might relate to woodworking—the words just felt appropriate—but in navigation intentional offset (also referred to as aiming off) basically means aiming to the left or right of a destination, so that you can then make a deliberate turn toward your target once you achieve a certain landmark. If you aimed directly for your destination and missed, you’d have no idea which direction to look in.
Now, in the US, actual professional carpenters who don’t rely on misappropriated sailing terms would call those offsets around the door casing and rafter trim a reveal. (Australian carpenters call it quirk, which is clearly the superior term.)
If you happen to be a finish carpenter, this post is going to seem pretty obvious. But for the rest of folks, this purposeful misalignment is a subtle design and building choice that’s easily overlooked. So I thought it was worth dissecting.
The Problems:
Wood moves. It bows, cups, shrinks, swells, and cracks.
We are not perfect. Our saw cuts are not perfect. And even if they were, all that moving and swelling would eventually render them imperfect.
Our eyes (and hands) are extremely effective at noticing imperfections alongside near perfection; if two edges are aligned in one spot, we will immediately notice where they become misaligned.
Imagine you’ve joined two cleanly cut boards together, crisp edge to crisp edge. It’s flawless. But in time, the wood will shrink and gaps will open here or there. One edge will ride higher than the other in an area or two. It will happen and those inconsistencies will shine. People will notice. You will notice. Those mistakes will cry out like a beacon and your shame will live in those gaps.
The Solution:
We own the mistake. We make the mistake so great that it’s obviously intentional and the degree of mistake gets lost in the shadows. We make no attempt to match the edges flush whatsoever.
The reason this solves the problem is because our eyes are extremely attuned to notice a gap when there shouldn’t be one, but we’re weirdly disinterested in discerning the varying size of an intentional discrepancy.
On a door or window reveal, the front-facing trim board’s edge might be roughly a quarter inch from the edge of the perpendicular trim board that meets the frame (that interior board is called the return, FYI). Over the length of these two boards that quarter inch will vary slightly, but our eyes won’t really pick it up unless we’re really looking for it—that variable distance flies under the radar.
You’ll notice on door and window trim that the head trim frequently overhangs the vertical trim. Same reasons… that head trim cut could never remain perfectly aligned with the edge of the vertical trim and would always look a little wrong if attempted, so we just own it and overhang the wood by some amount that has an appropriate visual weight that feels correct. It’s a technique born of practicality and is now so commonplace that if you don’t do it, something might feel off.
On the previously pictured rafters and skylights theres no way those big trim boards could remain flush against the rafter’s edge for the entire length. And they are sure to cup and pull away in a few zones over time. So the craftsman owned it and made the trim significantly shorter, creating a lot of visual wiggle room. However much those wide planks shift and drift from their attachment and alignment, it’s okay because they very clearly were intended to be far from perfectly paired.
That intentional cascade in height has the added benefit of creating some texture and shadow that calls to a familiar and comforting architectural language which embraces the multiple layers of finish carpentry. We don’t really think about it or notice it necessarily, but it feels right because this is just the way things are built.
Deck boards are gapped (and sometimes rounded over), in part, for these same reasons. For drainage and swelling, yes. But also, because tight boards would never be fully tight and those that parted would stand out like a sore thumb. Gaps and offsets are soothing. They have an evening effect. Consistently inconsistent.
Indoors, rain-soaked boards are less of an issue, but it’s still effectively impossible to perfectly mate the planks on a wall edge-to-edge. So the best choice is to lean in and space them from one another to mask the variances in proximity. On this house with locally milled boards, it was a practical and playful choice to run extra-wide gaps. In other homes, which might use more precisely moulded and kiln-dried tongue and groove cladding, these would still likely have a gap or V-groove that creates a channel for minor inconsistencies to disappear into.
The coping around the rustic log post is yet another example. Again, any attempt to make this union perfect is sure to fail as the tight connections of some boards would just draw attention to those cuts that came up short. So instead, these builders left an intentional gap, and while it might wander a few millimeters tighter or looser, your eye won’t register it. Especially when paired with the similarly sized horizontal gaps between the boards.
In the cases where it does make more sense to butt two pieces edge-to-edge, there are techniques often used to mask the inevitable imperfections. Different sizes of wood, grooves, rounded edges, bevels, chamfers… these are all applied to induce shadows and a perceived intentional gap that will confuse the eye and blur the irregularity of the edges.
Look around your home and you’ll find a lot of these little intentional offsets. If you’re the type of self-taught builder who might trim a window, build a shed, or install some shelves in the garage, it’ll be useful knowledge, and may not have been obvious. It certainly wasn’t to me for a time. Your understandable instinct might be to line up two pieces of wood just so. Or to match two sizes of wood exactly. But now you’re off the hook.
It’s something I take comfort in. Intentional offset is permission to steer away from perfect because doing so would actually be a mistake. Aim for perfect and you don’t know where you’ll land and exactly how you’ll miss. But if you aim for roughly a quarter inch off to the left with some wiggle room for however things shake out, you kinda know right where you’ll end up.
Edit: Some clarifying context from my friend Cliff, who attended furniture school, is a very talented professional builder—and most importantly—actually knows what he’s talking about:
“Shadow gap is a term used when you have a joint with two chamfered edges. You intentionally create a visual where you can’t tell if the gap opens up or not and it’s harder to tell when the edges are beveled.”
Double Edit: Seems like I got “Intentional offset” as a carpentry term from my friend Tom. He said he’s used it for a long time and I’ve learned a whole lot about woodworking from him, so I must have soaked it up somewhere along the way.
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