Material Selection, Handling and Preparation
This domain tests whether you can choose the right stock for the job, predict how it will move, and store and prepare it so it stays flat and stable until installation. Questions mix species and panel knowledge with moisture content and handling practice, and they often hinge on wood movement arithmetic.
Solid wood
- Hardwoods (oak, maple, cherry, walnut) versus softwoods (pine, fir, spruce); density and hardness decide wear resistance, and shrinkage behaviour decides panel design.
- Grain orientation matters: flat-sawn shows cathedral figure and moves most in width; quarter-sawn and rift-sawn are more stable and show straighter grain.
- Lumber grading follows NHLA rules for hardwoods (FAS, Select, No. 1 Common) and NLGA for softwoods; grade limits defects, not moisture.
- Kiln-dried interior stock should sit around 6 to 8 percent moisture content, in equilibrium with a conditioned space at roughly 35 to 45 percent relative humidity.
Panel products
- Plywood, MDF, particleboard, veneer core, MDF core and combi core each machine and hold fasteners differently; MDF takes a clean edge but swells if it gets wet.
- Formaldehyde emissions for composite panels are regulated (TSCA Title VI in North America); ask for compliant documentation.
- Backing, balancing veneer and edgebanding selection all affect whether a panel stays flat.
Handling and preparation
- Store sheet goods flat and off the floor; store solid stock flat, stickered, with air flow, out of direct sun and away from heat sources.
- Acclimatize material in the conditioned space before machining and finishing.
- Check for warp, twist, cup and bow; cut oversize and dress to final dimension only after the stock has settled.
Worked example
A 300 mm wide flat-sawn red oak panel goes from 8 percent to 12 percent moisture content after delivery. Using a dimensional change coefficient of about 0.0037 per 1 percent for flat grain: 300 × 0.0037 × 4 = 4.4 mm of movement. That is why a solid panel needs roughly 2 mm of clearance per side in its groove, and why you never glue a panel along its full width. Quartersawn stock at about 0.0019 would move roughly half as much.
Traps that cost marks
- Assuming plywood does not move at all - it moves far less than solid wood, but it is not zero.
- Cutting to final size before acclimatizing, then finding the parts have shrunk.
- Specifying MDF for a wet or humid location.
- Forgetting that finish adds thickness and that veneered edges need protection.