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What is Wood Movement?

Temperature and humidity may affect the degree of wood movement.
Older boards may move less than recently cut boards.
Plywood experiences very little wood movement.
MDF typically doesn\'t exhibit much expansion or contraction.
How a wood was cut, such as quartersawn or plainsawn, affects wood movement.
Melamine covered particle board, which has very little wood movement.
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  • Written By: L. S. Wynn
  • Edited By: L. S. Wynn
  • Last Modified Date: 24 August 2014
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Wood has many desirable features that make it the material of choice for many projects, especially furniture-making. Despite the beauty, durability and workability of wood, it does have some disadvantages. One of the most difficult characteristics to manage is called wood movement. This is when the wood expands and contracts, potentially causing gaps or bowing in the finished product.

When wood is examined under a microscope, the structure resembles a multitude of tiny parallel tubes. These passageways were used to transmit nutrients when the wood was a part of a tree. Once wood is cut out of a log, these tubes tend to expand and contract in conjunction with temperature and humidity changes.

Wood tends to experience the majority of its expansion and contraction in one particular direction. Movement parallel with the grain is negligible, whereas expansion and contraction across the grain is significant.

The rate of expansion and contraction of wood varies from species to species and even from board to board. The amount of movement also seems to decline with age, so an older board may move less than a recently cut one. A general rule of thumb that most woodworkers use is that boards can move up to 1/16 inch per foot (1 mm per 20 cm) perpendicular to the grain, and sometimes more.

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In small projects, the amount of wood movement is often insignificant and can safely be ignored. When larger surfaces are mated, however, these variations must be taken into consideration. When mounting a large table top to a base, for example, the potential for expansion and contraction can approach 1/2 inch (13 mm). If the woodworker fixedly mounted the top, the wood would crack or bow and the table would be weakened or ruined.

Woodworkers have developed all sorts of techniques to mitigate the problems associated with wood movement. They may use slip joints, oblong holes or special fasteners (such as figure-8 fasteners) to join large boards or panels.

The way in which a particular board was originally cut, also plays a role in the expansion and contraction that it will experience. Quartersawn boards, for example, undergo much less movement than their plainsawn counterparts. Alternatively, manufactured panels, such as plywood, particle board, or MDF, include so much glue that expansion and contraction is virtually nonexistent.

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anon173193
Post 6

@anon42493: Your friends are quite right and anon48842 is wrong. If you use such a large solid frame beneath the veneer. there is every chance it will telegraph through and be visible.

You should try to keep the framing/edging as narrow as possible probably no more than 10mm if you can. In addition it pays to cross band veneer first that is have two layers of veneer the first running 90 degrees to your finished veneer skin. that will help reduce the likelihood of the edging telegraphing. Construct very similar to plywood.

One more issue you should consider is that MDF does actually expand and contract with variation in moisture content as with all wood based products. MDF is very prone to movement in thickness so be aware.

anon48843
Post 4

bstavis - there is no way to treat wood to keep it from expanding/contracting.

anon48842
Post 3

anon4243 - the MDF substrate will not expand/contract. The veneer will try, but assuming it is less than 1/8 inch thick, and well glued, it will not move. If the veneer overlays both the MDF and frame, and is glued to both, then you won't see the joint between the frame and MDF.

anon42493
Post 2

I am making a conference table for a client 12feet by 4 feet. The table top is 1 1/2 inch MDF which was veneered (mahogany and some decorative inlays all around the top perimeter). The entire table was framed all around 1 1/2 inch thick by 3" wide solid Mahogany prior to the application of my veneer surface. The solid Mahogany frame is plain cut (not quarter sawn). The veneer was glued with white glue in a hot plate press. My question is: will I have problems with the solid frame expanding underneath the mahogany veneer? A number of my friends (old guys --D) who have a lot more experience told me that the joint between the solid mahogany and MDF will telegraph right through and thus show under the catalyzed polyurethane finish. Can you please give me your expert opinion about this nagging question that has been tormenting me for the last few days. I am about to start doing the base for that beautiful table but it makes me worry to think that all the work done will lead to a possible disaster. Thanks in advance.

bstavis
Post 1

Concerning expansion and contraction of wood, is there any way of treating wood to reduce the expansion and contraction?

I'm thinking in particular of a wooden (mahogany) rudder on a boat, which absorbs lots of water during the sailing season and expands, and then drys out and contracts when the boat is out of the water for the winter (or longer).

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