Allowing for Wood Expansion on Solid Wood Tops

ENJOY THIS FREE VIDEO!

Watch even more great videos when you become a WWGOA Member!
  • Choose Your Membership Plan
  • Bonus Video Downloads
  • New Videos Every Week
  • View on Computer or Mobile
Learn More

Wood moves; there’s nothing you can do about it. Even after the tree is down, the wood has been dried, you’ve got it in your shop, and you apply finish, wood is gonna move. It’s a living, breathing thing. If you don’t allow for wood expansion, you’re going to have problems in the future. Problems being cracking, splitting, maybe even blowing a leg and rail assembly apart. Let’s not let that happen.

Do’s and Don’ts

To give solid wood pieces plenty of opportunity for wood expansion, here’s a list of things you should and shouldn’t do:

  • Don’t glue a solid wood top to the rails in the base.
  • Don’t screw the top in place, unless the screw holes have sufficient wiggle room to allow for wood expansion.
  • Do use tabletop fasteners. They’re easy to use, and allow wood movement by sliding along a kerf in the rail as the solid wood expands and contracts.
  • Don’t worry about plywood or other man-made slabs. They don’t have the seasonal movement that solid wood does.

Direction Matters

Wood only expands and contracts in one direction; perpendicular to the grain. Depending on the specie of wood you’re working with, it can move as much as ¼”, or even more. You don’t need to worry about expansion and contraction parallel to the grain.

More Great Info

Hey, here at WoodWorkers Guild of America we want to help you do good work. This is just one example of the helpful shop tips we provide on a regular basis. Be sure you check out the rest of our archive.

Discussion
  • (will not be published)

15 Responses to “Allowing for Wood Expansion on Solid Wood Tops”
  1. Denis Lock

    To describe wood in your shop as a “living, breathing thing” is totally incorrect. Long before a tree is felled a high percentage of the cells (the heartwood) are dead. The correct description is “hygroscopic”.

    Reply
  2. Arthur Smith (Australia)

    If the applied finish on a surface like the table top used in your demo is also constantly expanding & contracting laterally will the finish not crack with the constant movement eg something like a laquer ?

    Reply
    • Customer Service

      Hi Arthur. Lacquer and other common finishing products have enough flexibility to them that they can accommodate the typical seasonal expansion and contraction of wood.
      Thanks
      Paul-WWGOA

      Reply
  3. Bobbg

    So the question is how much down holding force? Loose so when I pick the unit up the top shifts, or snug enough it won’t move? Basicly how much movement force will a top provide, and I’m sure different types of wood move more depending how hard a wood it is.

    Reply
    • Customer Service

      You want to tighten the fasteners enough so that the top won’t shift when you move it. Even with moderate holding pressure, the table top will still be allowed to expand and contract with seasonal movement. Just don’t tighten them with extreme pressure.
      Thanks
      Paul-WWGOA

      Reply
  4. Rick Burgess

    What about plywood tops? I am making a couple of demi-lune tables, approx 36″ wide by 20″ deep. The tops are edge-banded with very thin veneer. Can I attach them to the rails with pocket screws, or should I allow for movement with plywood tops also?

    Reply
    • Customer Service

      Hi Rick. Great question. No, you do not need to allow for movement with a plywood top.
      Thanks
      Paul-WWGOA

      Reply
    • Customer Service

      Hi Gary. A pocket hole screw would not allow for expansion and contraction, so I would not recommend this approach for attaching a solid wood top.
      Thanks
      Paul-WWGOA

      Reply
  5. keith

    As someone who’s repaired a lot of furniture, the Chinese furniture factories either need to know this or need to care. I’ve had customers who say, “We awoken in the middle of the night with what sounded like a gunshot. We came out and found this giant crack all down the top of our dining table.

    “You can’t control wood movement, you can only account for it.”

    Reply
  6. Matt Thie

    How would you incorporate this into a table with a round base, especially circular? If the shape is more of an oval or if the radius of the circle is large enough, then I would assume you just don’t put the clip all the way into the kerf so that it still has a little room at the tip to move within the curve? What about when you have a tight radius at the end that would be perpendicular (or a tangent line would be perpendicular) to the grain, for instance if you have a long narrow coffee table, sofa-back table, bar top, etc.–cut a deeper kerf (if possible) to give more lateral room for movement?

    Also, you said not to glue or screw the top to the table base, and in another comment you advise against putting in even a single screw in the middle–how is this different from breadboard ends, where you have said in other videos to glue only the center portion (center 1/3 or so) in order to allow for expansion at the edges? Wouldn’t a solid top and a top made from multiple pieces glued along the edges both expand and contract similarly? Why glue one in the center and not the other?

    Reply
    • Customer Service

      Hi Matt. I think the idea is to allow a reasonable amount of wood movement in any direction that it could possibly move. You are correct in stating that you would pull the clip just partially into the kerf. You can make some guesses as to whether the board is more likely to expand or contract in the future based upon the season you are building in, but I just try to get it approximately in the middle if its travel in most cases and I’ve never had a problem. Cutting a deeper kerf is useful if you have the material to do so.
      You can install a screw into the middle of a rail on the end grain but not the long grain. You’re right, this is the same principle as a breadboard end. A top made of glue up pieces will expand and contract in the same way that a single board will.
      Thanks
      Paul-WWGOA

      Reply
  7. Chris

    I’m just getting started on a sofa coffee table and am so glad I saw this video as the plans called for pocket holes all along the perimeter. One question I have though, the plans call for a lower shelf that is not quite as deep as the lower stringers. I’m guessing I should allow for the same expansion/contraction on the lower shelf as the table top itself. Would the best way to place the kerf in the middle section of the stringers be to drill press and chisel them? I guess I could alter the plans and make the shelf the full depth but I like the look it offers being slightly smaller.

    Reply
    • Customer Service

      Hi Chris. If the shelf is solid wood, then you will need to accommodate wood movement there as well. Your idea to drill press and chisel should work fine.
      Thanks
      Paul-WWGOA

      Reply

Tags: Free Videos, free woodworking videos, wood expansion, wood grain, woodworking tips, woodworking videos, wwgoa