Buying Timber (What to Check Before You Build)

What this guide covers

Buying timber well is a skill. This guide gives a simple checklist so you can pick boards that will stay stable, machine cleanly, and fit the job.

The 3 questions to answer before you buy

1. What environment will this live in?

• Indoors heated
• Indoors but damp
• Outdoors above ground
• Outdoors ground contact

1. What matters most for this project?

• Strength
• Stability
• Durability
• Appearance

1. What process will you use?

• Hand tools, power tools, or both
• Will it be planed down heavily?
• Will it be glued up?

<aside> ✅

If you do nothing else: buy timber that is dry enough for the final environment, graded appropriately, and treated only when needed.

</aside>

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Step 1: Choose the right type of timber supply

• Construction timber (CLS, studs, carcassing): cheap, often fast-grown, usually strength graded, often wetter or less stable.
• Joinery timber: selected for straighter grain and fewer defects. More predictable.
• Hardwood boards: wider range of species and figure, often sold by thickness (e.g. 1", 2") and by volume.
• Sheet goods: stable and efficient for panels. Not "timber" but often the better material choice.

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Step 2: Moisture content (MC) — the non-negotiable

You are not buying a board. You are buying a board at a moisture content.

Quick targets (typical)

• Heated interiors: ~6–10% MC
• Unheated interiors / sheds: ~10–14% MC
• Outdoor work: varies widely, but the key is that it should be stable for its use class and detailed correctly.

What to ask / check

• Was it kiln dried or air dried?
• What MC is it leaving the yard at?
• Has it been stored inside or under cover?

What to do if it is too wet

• Do not build immediately.
• Bring it into the workshop.
• Sticker and weigh it down.
• Let it acclimate until it is near the shop EMC.

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Step 3: Grading and what the stamp actually means

Strength grading (e.g. C16, C24) tells you structural capacity, not beauty.

If it is stamped

• Read the stamp for:
• Grade (e.g. C24)
• Species group
• Standard / mill
• Sometimes treatment and use class

If it is not stamped

You are relying on:

• The supplier’s selection
• Your own defect checks

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Step 4: Dimensions — nominal vs finished sizes

Many softwood products are sold by nominal size but arrive smaller when planed.

Checklist:

• Confirm the finished size (actual thickness × width).
• If you need a final thickness, buy with enough margin for flattening.

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Step 5: Defect checks (fast yard inspection)

Pick boards like you are trying to predict the future.

Look down the length:

• Bow
• Crook
• Twist

Check the ends:

• End checks and splits
• Growth ring orientation (helps predict cupping)

Inspect faces/edges:

• Knots (size, type, and position)
• Wane (missing arris)
• Resin pockets
• Shake

<aside> 🧠

A few small knots can be fine. A big knot near an edge in a narrow piece is often a failure point.

</aside>

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Step 6: Treatment and durability (buying for outdoors)

• Prefer design and detailing first.
• Treat when exposure demands it.

Checklist:

• Identify use class for the job.
• Confirm treatment type and penetration.
• Avoid mixing treated and untreated in ways that trap moisture.

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Step 7: Storage and acclimation after purchase

• Sticker it.
• Keep it off concrete.
• Keep airflow around the stack.
• Let it acclimate before final milling.

Simple buying checklist (copy/paste)

• Intended environment is clear (indoor / outdoor / ground contact)
• MC is appropriate for that environment
• Grade is suitable (strength vs joinery selection)
• Dimensions confirmed (nominal vs finished)
• Boards inspected for warp, checks, knots, and wane
• Treatment only if needed, and correct for the use class
• Plan for storage and acclimation at home

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🔗 Knowledge Network

Glossary Terms

• Moisture content (MC)
• Equilibrium moisture content (EMC)
• Kiln dried (KD)
• Air dried (AD)
• Green timber
• Strength grading
• Nominal size
• Finished size
• Wane
• Checks and splits
• Warp (bow, crook, cup, twist)
• Use class / hazard class
• Penetration
• Retention

Related Timber Species

• Spruce (typical structural softwood)
• Pine (softwood joinery and construction)
• Douglas fir (stronger structural softwood)
• Larch (often used outdoors)
• Oak (common hardwood benchmark)

Calculators

• None for this guide

Related Guides

• Track 4 – Guide 5 – Moisture Meters and Measuring MC
• Track 4 – Guide 6 – Storage, Acclimation, and Handling Timber
• Track 4 – Guide 7 – Timber Grading (Strength, Defects, and Stamps)
• Track 4 – Guide 8 – Planed vs Rough Sawn (Nominal vs Finished Sizes)
• Track 4 – Guide 9 – Timber Treatment & Protection (Use Classes, UC Ratings, and When to Treat)

Fact-Check Report — Guide 10: Buying Timber