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back-up data about hardwood warping

1/9/15       
Woodworker2090 Member

Hello, I'm working on a project where the client wants to face nail rough sawn Red Oak planks he had kiln dried himself from trees that fell on his property. He wants of random widths of 4/4 at 8", 10" 12" by 10' nailed to plywood panels in his dining room. Its a large dining room with windows and doors.

I am advising against using such large widths because of my experiences but he wants back-up from some authority stating the reasons and tolerances.

I have scoured the internet and find loads about grading but not much about the problems of using unfinished lumber for interior paneling.

Does anyone know a resource for finding the tolerances of warping in hardwoods?

How can I explain that using boards that wide is not the best idea?

In your opinion what widths are safe and stable to use? i don't want to use boards over 6".

1/9/15       #2: back-up data about hardwood warping ...
David R Sochar Member

Wide boards have been used for wall paneling for centuries, but they should be used in such a way as to accommodate wood movement. Nailing them to plywood would not be considered successful for most people.

First thing is to meter the boards with your moisture meter to see what the current MC is. Then consider the installation environment - new construction? Lived in house? One will have swings in humidity and therefore equilibrium moisture content, and the latter will be more stable. You do not want this stuff to go into the room until it is stable.

Next, look up in the Shrinkulator to see what will happen with your boards. If you are in the major part of the US, the boards will settle down at about 6.5% MC.

However, the wood will continue to move with normal seasonal variations. The Shrinkulator will again help you know what to expect.

Yes, the finish will slow down the movement somewhat, but will not eliminate it. Doesn't matter how much finish you apply, it will still move. Then there will be the week the in-laws come to visit and take 18 showers a day, and cook all day, as well as shampoo the rugs and paint a few rooms. The humidity will go sky high, and your boards will move in response. So plan on some room for the eventualities.

Tongue and groove, shiplap, and frame and panel are all methods that help deal with wood movement. They are considered mostly decorative nowadays, but the reason for those joints/styles is based on the technical nature of wood movement.

Shrinkulator

1/9/15       #3: back-up data about hardwood warping ...
Geoff

I don't have links for you but there is a book by Bruce Hoadly that explains wood movement that you could show your client. Also, The Wood Doctor has some articles explaining seasonal wood movement.

That said, I think you can do what the client wants. First, like David said, make sure the wood is equalized MC to the humidity in the room. Two, somehow allow for expansion and contraction in the boards (two six inch boards are going to move just as much as one twelve inch board). I wouldn't nail the boards to plywood. I would use some kind of strapping so that there is air movement on both sides of the boards.

Are we over thinking this? Maybe the client is right. Have you ever seen wide plank pine floorboards nail directly to the subfloor...Just a thought.

1/10/15       #4: back-up data about hardwood warping ...
Carl Hagstrom

You may want to peruse the wood movement related articles in our Knowledge Base to glean some helpful information - I've included the link below

Hope this is of help

Carl Hagstrom
Systems Administrator at WOODWEB

Wood Movement articles

1/10/15       #5: back-up data about hardwood warping ...
Adam

I've seen numerous wide pine plank floors. I mean between 12" and 24" wide. The thing all of those floors have in common is they all split on the fasteners and they were installed with huge gaps between the planks, often 1/2".

Personally, I would not be too concerned about widths less than 12". We can accurately calculate the expansion in width. As David noted you need to have a good idea of how wet the wood is before you gap it. The owner should already own a moisture meter if he is drying his own timber.

Most people have seen improperly laid decking. In some cases the decking is hitting each other when wet , on others there are 1/4" gaps between the decking boards when dry. The installer probably gapped them, but had no idea if the wood was wet or dry.

The cupping will happen no matter what you do, so it needs to be installed consistently so that it cups out or in.

I would argue for a nail that has a large head and smaller shank. Drill the holes oversized to prevent splitting at each fastener location.

At the end of the day, the customer is always right until they are wrong. If you warned them in the first place then they own it.

1/11/15       #6: back-up data about hardwood warping ...
Larry

Warn in writing! Wood moves in response to it's environment. You can't stop it, just accommodate it. Wide boards will show more cup than narrow ones. The amount of change in the width and the amount of change in cup will depend on the changes in equilibrium moisture changes. Does he care if the gaps change or are you going to try to conceal the gaps? Just accommodate them one way or the other and make sure he understands wood moves.

1/12/15       #7: back-up data about hardwood warping ...
Gerry

I would invest in this chart from Lee Valley I think it is well worth the $10.00 (see link below). Then check the moisture of the lumber and gauge the movement when it reaches 6 to 7% You can also estimate seasonal movement for various species.

Gerry

Lee Valley chart


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