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How Wood Moves with Humidity

Solid wood shrinks and swells with humidity mostly across the grain — almost not along the length. Tangential movement (parallel to the growth rings) is usually larger than radial movement (toward the pith). At Fells Hardwood Supply in Hutto we help furniture makers pick cut and species with that in mind, then design tabletops and panels so they can float through Central Texas seasons.

What actually changes size

Think of a board as a rectangle. Along the grain (length), dimensional change is tiny for furniture work. Across the grain (width), the board gains and loses moisture and changes size. Thickness also moves, but the problem you feel on a tabletop is usually width: a panel locked to a rigid base will cup, crack, or tear fasteners when the seasons swing.

Rough rule of thumb from wood science: tangential shrinkage runs nearly twice radial shrinkage for many hardwoods. That is why plain-sawn (flat-sawn) faces — rings roughly parallel to the face — move more across the width than quartersawn faces, where rings run more through the thickness.

End-grain log with tangential and radial arrows; board views for plain and quarter sawn radial tangential (more) End of a log On a board plain sawn · rings // face more width movement quartersawn · rings ⊥ face calmer across width
Tangential change (along the rings) is usually larger than radial. Plain-sawn faces put more of that movement into the board’s width.

What matters for furniture and tabletops

For a dining top or wide panel, design for seasonal width change, not for a single published percentage that ignores your house. Leave room to move: elongated screw holes, figure-8 fasteners, breadboard ends with slotted pins, or other floating attachments. Do not glue a wide solid top rigidly to a fixed apron all the way around.

Quartersawn and rift stock generally move less across the width than flatsawn cathedral grain, but no solid top is “stable forever.” Indoor furniture wants kiln-dried stock near furniture moisture content (often about 6–8%), then time to acclimate in your shop before final milling and finish. Skipping acclimation is how tops cup after a week in the dining room.

Tabletop width grows in humid air and shrinks in dry air; length stays nearly the same Across the grain (width) ← → Along the grain (length): almost no seasonal change Leave the top free to float on the base
Width is the furniture problem. Length barely moves — so fasteners and breadboards should allow cross-grain float.

Central Texas humidity swings

Garage shops around Austin and Hutto can be humid while dining rooms sit in heavy air conditioning. That delta matters more than a lab chart for “oak percent.” Acclimate the lumber where the piece will live when you can, mill and finish after it settles, and still design mechanical float for the seasons ahead.

Short shopper FAQ with attachment diagrams: How much wood movement for tabletops? Sawing cut and why plain vs quarter behaves differently: How hardwood logs are cut.

When you shop at Fells Hardwood Supply, tell us finished width and where the table will live. We help weigh cut (plain / quarter / rift), species, and thickness against movement — not just looks.

Back to Learn · Tabletop movement FAQ · Kiln dried vs air dried