# wood expansion



## mayday3374 (Feb 29, 2008)

forgive me for the 20 questions, but i am still learning as i go. we all know that wood expands and contracts with climate change, but there are 2 things that i cant figure out. first of all, how much does the wood expand and contract if it is an indoor piece, and secondly, what kind of construction methods need to be taken into account when building a basic cabinet to allow for this expansion? i am building a wine cabinet. it is a open front, the 2 sides are 3/4" thick maple boards, 15" wide. the actual shelves are seperate front and rear pieces. they will be secured to the sides of the cabinet using dowels. there will be a small drawer above the shelving to hold the wine openers and a couple towels. the rear is a panel that will be 1/4" thick, housed in a 3/4' thick frame. the entire panel will be nailed into the sides. i am worried that i will spend alot of time and money making a nice tight piece of furniture, only to watch the climate pull it apart at the seams. i dont fully understand what techniques should be used when building/ designing a piece that allows for expansion. please help or direct me to some good reading. thank you


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## cabinetman (Jul 5, 2007)

It's for the reason you stated that most cabinets are not made with solid lumber. With all the varieties of sheet stock, and how stable it is, makes for a more predictable cabinet.

For in the house, humidity and temperature can be a factor. Also, where you place furniture in relation to windows, doors, A/C vents, etc. If you live in the North, and then pick up and move to the South, or South to North, may have a bearing on a piece of furniture.


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## MoonRoc (Apr 11, 2008)

I am new to the forum but have been doing woodworking for a while. The best way to find out is to build it to the best of your ability and learn from it. Take what you have learned and apply it to the next piece. Some of the best pieces I have built were early ones. The gaps and imperfections give them a character, more of a hand built look. Enjoy it.


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## ED HORNER (Apr 8, 2008)

I recently took a small cabinet job on. The customer is a timber cutter. He "gave" me the material, some crummy thick oak he milled on a very dull planer. It was some pretty awful looking stuff,but i worked and culled and worked some "much" more. The client knew I wasnt a cabinetmaker but gave me the job to keep me working. Basic plywood boxes with the oak faces and raised panel doors. I used the tablesaw trick to make the panels, and glued and clamped and sanded and stained and cleared some very attactive handmade cabinets. Got paid and all. Well long story longer, the bathroom linen closet cab had a steam generator later installed. the heat and cooling cycles haved moved the panels constantly. Bare wood on the panel edges have made for many visits with the client. Should have stained them first. But the glued joints are as tight as new. Damn floating panels. Its just that one set of doors haunting me, and the final lesson was learned.... I gave the owners the can of stain and a rag. they laughed and were still happy with those "walking panels".


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## Gerry KIERNAN (Apr 20, 2007)

Okay, I have to ask these questions. If the edges of panels are stained/sealed, prior to assembly of the cabinet doors, and then the complete door is stained /sealed after assembly will this prevent the panels from expanding/contracting with humidity changes, or simply reduce the amount of movement? I want to build some raised panel doors from Western red cedar which I have, and this is something that I hadn't thought of. I know that WRC is not nearly as prone to climate changes as many woods, but it would move some, I am sure. I plan to finish them in their natural colour, and seal with satin varathane. Also, how much should the panels extend into the door frames to ensure that they don't fall out with extreme contraction? How much free space should I allow for expansion in high humidity?

Gerry


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## Graphiti (Mar 29, 2008)

Gerry, it is virtually impossible to seal wood in such a way as to eliminate absorbtion and release of moisture in the form of air humidity. Even the best sealers allow some moisture movement because the surface finish will be permiable to some degree. Think of a Helium balloon. When a balloon is filled with Helium it deflates more quickly than one filled with air. This is because the molecule that forms the Helium is physically smaller than the air and is able to pass slowly through the skin of the balloon. With moisture it is the same principle, water vapor is small enough to penatrate the minutely porous surface and allow the wood to absorb and release moisture. This is why when you get a sealed piece of wood wet it doesn't absorb into the wood, the molecules of water are just too big. 

As far as the room to expand and contract, I leave 3/16" around the perimeter on 12" to 24" panels if the air moisture is average. In high humidity I close the gap to 1/8" and when it's dry I up it to 1/4". Of course I fill the gap with rubber spacers so the panel doesn't rattle.

And as far as the panel extending into the frame, I plow the groove about 5/8" deep and center the panel with the spacers. This allows 3/8" overlap to be the minimum even in very dry regions.
Hope I was helpful,
Randy


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## cabinetman (Jul 5, 2007)

Gerry KIERNAN said:


> Okay, I have to ask these questions. If the edges of panels are stained/sealed, prior to assembly of the cabinet doors, and then the complete door is stained /sealed after assembly will this prevent the panels from expanding/contracting with humidity changes, or simply reduce the amount of movement? I want to build some raised panel doors from Western red cedar which I have, and this is something that I hadn't thought of. I know that WRC is not nearly as prone to climate changes as many woods, but it would move some, I am sure. I plan to finish them in their natural colour, and seal with satin varathane. Also, how much should the panels extend into the door frames to ensure that they don't fall out with extreme contraction? How much free space should I allow for expansion in high humidity?
> 
> Gerry



If you're concerned about panel movement THIS THREAD may help. Wood movement could have nothing to do with transfer of moisture. Lets assume you completely seal the panel, by many dips into a tank of oil base polyurethane, or 125 coats of nitrocellulose lacquer, so that there is absolutely no way moisture can get in or out. 

Moisture not getting in (absorbing) and not getting out (emitting) is a problem. For whatever innate moisture is retained in the cells of the wood, that condition alone will allow the wood to react in any way it finds necessary dealing with what's retained (trapped). 

For moisture not being able to get in, will affect those areas that dry out because of a lack of moisture, and it being drawn to other areas. So, I'm not going to talk about molecule size or air pressure, relative humidity, hot air rising, or movement of the Earth. What I will say is that Mother Nature will do as she pleases, and we as humans take our chances. I guess that's what makes the world go 'round.


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## Gerry KIERNAN (Apr 20, 2007)

Thank you for you very good answers Graphiti, and cabinetman. This gives me a very good start. I didn't think there was any way to totally seal wood, but I had to ask. The raised panels I want to do will be 12 inches wide by 24 inches high. This should make the resulting doors about 16 inches by 28 inches.

Thanks again.

Gerry


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