The table top.  I’m looking for thoughts should anyone offer them up…

So on paper, I drew up this outdoor table to hold my grill. I purposefully used the same joinery techniques that I’m using for my indoor living room table (yet to be finished); practice the through tenons to attach the tabletop on an outdoor piece prior to doing it on the real thing (the indoor piece).

The goal of this project (from its inception): Build a simple outdoor table to hold my grill (to prevent it from tipping) using bomb-proof joinery.  I don’t care if it has flaws or what type of wood it’s made of (so long as it’s strong)… and it’s a requirement to keep the price under $1000.  Furthermore, I don’t necessarily care if the top is flat, so long as it holds my beer while I cook.  Lastly, the lifespan of the table is the lifespan of the grill; once I get rid of the grill, I’ll have no use for a table with a big hole in the top.  I put the lifespan in the 15-20 year timeframe.

So I have a co-worker that spent 3 months (three!!!) apprenticing under David Charlesworth, and it took a point-out from him to catch a major flaw that I completely missed in the designing of the table.  Take a look:

Wood movement

Table topWood moves.  Once he pointed that out, I looked it up: with seasonal movement, the front-to-back portion of the table top will contract and expand up to ¼” either direction (maybe even more).  Over time (maybe a year, maybe ten years), the tabletop will either crack, warp, or pull the upper fox-wedged tenons slightly out of their socket, weakening the joint.  Fortunately, the living room table I designed this thing after (at right) has a different top (it’s not one solid piece of wood) that allows through-tenons to secure the table top into place without the worry of movement.

What to do, what to do…

Here are the facts:

  • the white oak top has been sitting outside, air drying, for a few years. I’m pretty sure it’s acclimated to the moisture content where I live now.  So for now, this should minimize the movement. (Who’s to say when I move in a few years how much the moisture content of the new location will affect it)
  • I plan on applying some type of liberal finish on the top to slow the movement down.  I know, I know; I can’t stop it… but maybe slowing it has the potential to prolong against any catastrophic failures?

So what do I do?  Here are the options I can think of:

  1. Leave aloneBuild to fail (I guess this is the best way to put it): proceed as planned knowing that the top will warp or weaken the upper joints that oppose the grain movement.  Like I said, this is an outdoor table whose lifespan will be that of the grill.  Again, it just has to be flat enough to hold a beer successfully while grilling.  I guess this way I can see wood movement in action (kinda like the experiments Brian was running over at Toolerable) and learn through failure to not plan like that again.
     
  2. Buttons & Figure 8sCut off the tenons that protrude from the base and find a movement-safe way to attach the top to the base.  Things I’ve seen are wooden “buttons” or metal figure-8 braces.  I hate to say it though: I really kinda liked the way through-tenons looked, and part of the reason I designed it that way was to give it a shot on the outdoor table before I do it on the indoor table (practice, if you will).
     
  3. Split the topRip the top down the center (where I initially book-matched it together!!) and attach it to the base as 2 pieces, still using the the four through-tenons as points of attachment. It will allow the top to expand and contract towards the middle of the table. A lift grip centered on the sides of the table will obviously lift the tabletop from the base and stress the through-tenons. Therefore, any lifting must be done via the front and back of the table (rather than the sides). I dunno if I like the idea (visually) of having it split down the middle.
    My co-worker did offer up that it can be ripped at an angle to attempt to hide the gap somewhat:
    Ways to rip

I’d be curious to hear what anyone has to say on how I should proceed… especially if you’ve had experience or horror stories with wood movement…

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  • Ralph J Boumenot

    Hi Snakeye,
    If it was me I was keep going the way you are. I look through tenons too and I would deal with any wood movement as and if it happens. Wood doesn’t always behave and do what it’s supposed to do.

    • Ralph, that’s the way I’m leaning to be honest… but there’s this little voice nagging me, saying “why are you planning to fail?” that keeps me hesitant.

      It’s comforting to know that I’m not the only one that thinks this way though (with the idea of continue as planned).

  • Jonas Jensen

    My suggestion would be to make the two stretchers with a dovetail on top, and then make a dovetail shaped dado (there is probably a more correct English term for that one) in the table top. Then you can continue the build without metallic fasteners and contain wood movement.
    If you have already finished the stretchers – then I suppose my suggestion is a little too late.
    Brgds
    Jonas

    • A sliding dovetail I think is what you mean… but, alas, the base is wedged, glued and secure…

  • RenaissanceWoodworker

    There is a fundamental thing toe consider here first. Outdoor furniture is not indoor furniture and the same design can not always be applied. The piece will be subject to more extreme conditions and a much wider range of conditions. The usual approach is to design the piece in such a way to shed water so there is no standing water to cause undue expansion/contraction. This is why most outdoor tables have slatted tops for the water to drain through. The individual pieces also allow for the expansion and contraction. The alternative could be to make a tongue and groove or ship lap top but then you will be trapping water in those joints and just asking for wood rot. If you keep the solid top then you would consider battens underneath that are attached with slotted holes to allow some movement while still keeping it somewhat flat. The through tenons on the post could still be done, but the the through part would be faux while the tenons underneath could be built to allow some movement. However the fact remains that a solid top will not allow water to drain away.

    Now to the elephant in the room. You are putting a grill??? on this wooden table? Am I understanding this right? You are cutting a hole in the top and setting the grill down into a wooden table top? Is anyone else getting nervous about this? Now forgetting about the fire hazard, the heat from the grill is going to do crazy things with wood movement. Namely causing the top to dry out completely and probaly check and crack. Now dead dry wood is essentially a vacuum just begging for moisture so the minute it has a chance when the grill cools off, it will suck in moisture so fast that warping, cracking, splintering, and all kinds of fun stuff can almost be guaranteed.

    • A lot to consider; thx for responding! I’ll definitely need some time to digest the wisdom. I do have a cover that fits the table dimensions to hopefully mitigate/minimize the standing water.

      The elephant: I know at face value it sounds like the stupidest idea in the world, but the grill is 1″ thick ceramic that has another inch-thick double wall inside it to hold charcoal, etc. My hot water tap yields hotter temperatures than the outside of this grill when in use – I can hold my hand on it indefinitely while cooking. The company even provides basic plans for & sells wooden tables (<—-linked) for it, I just don't feel like shelling out doe for over-charged, shoddy (screwed together) joinery.

  • Brian Eve

    I like Shannon’s idea of Faux through tenons. I would use home-made buttons underneath. I think it might not be a bad idea to over-engineer this one as it is outdoors, I would suspect wood movement to be more drastic than your couch table.

    • I think what I’m gonna do is this:
      – keep the top one solid slab
      – use through-tenons to attach the top to the front of the base
      – use home-made buttons to attach the top to the back of the base while using faux through-tenons in the back.
      This way, at least I’ll get to practice what I wanted to in the first place: through-tenons in a table top.

      How’s you’re break been by the way?