Another question about wood movement t

[Randy C]

If you have a panel built out of 2 by 6 by 22 “ long red oak boards that  you assemble side by side in order to have a panel that is 8ft long when finished, do you still have to worry about wood movement if you completely seal every exterior surface of the wood panel with something like poly. Would the wood still expand across the grain or would the sealing with poly stop wood movement and expansion?

Thanks

[fredhargis]

Yes, it will still move. Think of all the table tops that are finished all over and they still plan for movememnt when doing things like breadboard ends and fastening the top to the frame.

[jteneyck]

To add to what Fred said, finish protects the wood from liquid water but does not stop the transfer of water vapor i.e. moisture.  So as the seasonally humidity changes, so will the moisture content of the wood, meaning it will expand and contract in response.  

You can control the overall length of your panel, and maintain exactly 8 ft, if you install the boards separately with a gap between them.  If you've ever heard of "nickel gap", that's what it's about.  1/16 - 3/32" gap between 6" wide boards should do it.    

John

[Ridgeway]

To add to what Fred said, finish protects the wood from liquid water but does not stop the transfer of water vapor i.e. moisture.  So as the seasonally humidity changes, so will the moisture content of the wood, meaning it will expand and contract in response.  

You can control the overall length of your panel, and maintain exactly 8 ft, if you install the boards separately with a gap between them.  If you've ever heard of "nickel gap", that's what it's about.  1/16 - 3/32" gap between 6" wide boards should do it.    

John

Won't that look like you are eating dinner on top of a railroad track though?  OTOH, if you glue up those 16 or so pieces, it is really gonna want to warp, in addition to growing a couple of inches every summer.

Not being snarky, but I'm thinking there is a reason people orient long boards lengthwise when making a table top.

[jteneyck]

Won't that look like you are eating dinner on top of a railroad track though?  OTOH, if you glue up those 16 or so pieces, it is really gonna want to warp, in addition to growing a couple of inches every summer.

Not being snarky, but I'm thinking there is a reason people orient long boards lengthwise when making a table top.

You didn't say you were building a table.  

I didn't say to glue the boards together.  Gap or no gap would make no difference if you glued the boards together.  

It doesn't matter which way you orient the boards when making a table - as long as you make provision for wood movement.  There are time tested ways to do that.  Get a good book on furniture design/construction.  

John

[CStan]

Finish won't stop movement and you've picked one of the worst species you could in terms of movement.

[Don_M]

If you have a panel built out of 2 by 6 by 22 “ long red oak boards that  you assemble side by side in order to have a panel that is 8ft long when finished, do you still have to worry about wood movement if you completely seal every exterior surface of the wood panel with something like poly. Would the wood still expand across the grain or would the sealing with poly stop wood movement and expansion?

Thanks

Randy – what are you building? (Doesn’t sound like a table to me – 2x6x22? That’s a narrow table!). Shrinkage depends on a number of factors; species, type of cut; quarter, rift or flat sawn (Q/S shrinks less) and average seasonal change in moisture content. There are lots of on-line wood shrinkage calculators – the one I have used in the past is the WoodWeb calculator. https://woodweb.com/cgi-bin/calculators/...=shrinkage



Assuming F/S red oak and a 5% change in average moisture content – for your your application total movement came out to be around 1½”



I make rear panels like this for cabinets all the time (Although not 2” th.). My preference is to  glue all the individual boards together into a solid panel ( I usually T&G the individual boards to help register them and keep them aligned and the overall panel flat/even). Fix/attach/glue the panel in the center and accommodate for the expansion at each end (that way you can split the shrinkage amount at each end (so in your case about ¾” at each end). Fortunately, I live in CA so we don’t usually get big swings in avg. moisture – so expansion (while I do accommodate for it) is not a huge problem

   

[Randy C]

Randy – what are you building? (Doesn’t sound like a table to me – 2x6x22? That’s a narrow table!). Shrinkage depends on a number of factors; species, type of cut; quarter, rift or flat sawn (Q/S shrinks less) and average seasonal change in moisture content. There are lots of on-line wood shrinkage calculators – the one I have used in the past is the WoodWeb calculator. https://woodweb.com/cgi-bin/calculators/...=shrinkage



Assuming F/S red oak and a 5% change in average moisture content – for your your application total movement came out to be around 1½”



I make rear panels like this for cabinets all the time (Although not 2” th.). My preference is to  glue all the individual boards together into a solid panel ( I usually T&G the individual boards to help register them and keep them aligned and the overall panel flat/even). Fix/attach/glue the panel in the center and accommodate for the expansion at each end (that way you can split the shrinkage amount at each end (so in your case about ¾” at each end). Fortunately, I live in CA so we don’t usually get big swings in avg. moisture – so expansion (while I do accommodate for it) is not a huge problem

Thanks Don for the info. What I am doing is trying to build a top for a corner workbench out of red oak from lumber that I had milled from my property. I  have decided to forgo the 2” material because I did not realistically think I could get it flat with my planer. Instead I am using one-by material that I have gotten planed down to about 8/10 “ thick. 

My plan is to glue up this panel and screw it to a 3/4” MDF panel that is attached to the framework of the bench. In regards to wood movement, my plan is to screw the front edge of the panel to the MDF from the underside (maybe 2” from the front edge of the panel). As I work back towards the wall, I will wallow out the screw holes in the MFF so the wood can expand towards the wall. I will cut the panel about 1/2 to 3/4 inches shy of the back wall. This crack will be unseen because I am going to attach a piece of plywood over it on the wall as an area to attach some hand tools. Does this sound like a sound plan to address the wood movement?

Thanks

[joe1086]

I might not understand this correctly, but if his table surface is 8' long constructed of 6" wide boards joined side to side, isn't the 5% movement closer to 4-5"?

[BrentDH]

I agree with Joe.  Your movement is not front to back if the grain of your boards is running front to back.  Your movement is side to side. Not sure it is as much as Joe suggested, but over 8’ of width it would be significant.