Woodworking

Why This Matters

Wood is the most available structural material on Earth. It grows everywhere, it is relatively easy to shape, and its strength-to-weight ratio rivals steel in some applications. Every civilization in history built with wood before anything else — houses, furniture, ships, carts, bridges, tools, weapons, printing presses, looms, and musical instruments. Metal tools let you cut it precisely. Joinery techniques let you build structures that last for centuries without a single nail. Mastering wood means you can build anything from a chair to a waterwheel to a sailing vessel.

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What You Need

Basic tool kit (minimum):

• An axe — for felling, splitting, and rough shaping (see Metalworking to forge one)
• A saw — crosscut for cutting across the grain, rip for cutting along the grain. Even a crude metal blade set in a wooden frame works.
• A knife or drawknife — for shaping, shaving, and finishing
• A chisel (1-2 cm and 2-3 cm widths) — for cutting joints
• A mallet — hardwood, about 1 kg, for driving chisels
• A drill — a bow drill or pump drill with metal bits, or a hand-cranked brace
• Measuring and marking: a straight stick (ruler), a piece of charcoal or awl (marker), a plumb bob (any weight on a string), a square (two straight sticks joined at 90 degrees)

Advanced tools (as your metalworking develops):

• A hand plane (a blade set in a wooden body at a fixed angle) — for smoothing surfaces
• A spokeshave — for rounding and shaping curved surfaces
• A froe — a heavy blade struck with a mallet to split wood along the grain (cleaving)
• A lathe (pole lathe or spring-pole lathe) — for turning round objects (bowls, spindles, handles)
• Clamps — wooden cam clamps, wedge clamps, or rope tourniquets for holding joints under pressure while glue dries

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Wood Selection

Choosing the right wood for the job is half the battle. Using softwood where you need hardwood (or vice versa) leads to failure.

Hardwoods vs Softwoods

Property	Hardwoods	Softwoods
Source	Deciduous trees (oak, maple, ash, hickory, walnut, elm, beech)	Coniferous trees (pine, spruce, fir, cedar, larch)
Density	Higher — heavier, harder to cut	Lower — lighter, easier to cut
Strength	Generally stronger, more durable	Generally weaker, less durable (exceptions: yew, larch)
Best for	Furniture, tools, wagon parts, structural joints, boat keels	Building frames, planking, scaffolding, shingles, light construction
Workability	Harder to cut but takes fine detail well	Easy to work but splinters more and holds joints less tightly
Rot resistance	Variable — oak and walnut are excellent; maple and beech are poor	Cedar and larch are excellent; pine and spruce are poor unless treated

Wood for Specific Applications

Application	Best Woods	Why
Tool handles (axe, hammer)	Hickory, ash	Flexible, absorbs shock, does not split on impact
Furniture	Oak, walnut, cherry, maple	Hard, durable, attractive grain
Building frames	Oak (heavy duty), pine/spruce (lighter)	Oak for permanence; softwoods for speed
Boat building	Oak (frame/keel), cedar/pine (planking)	Oak resists rot in water; cedar is light and rot-resistant
Cart wheels	Elm (hub), oak (spokes), ash (rim)	Elm resists splitting under compression; oak is strong in tension
Carving	Basswood, butternut, pine	Soft, even-grained, easy to carve with hand tools
Bows	Yew, osage orange, ash, elm	Flexible, strong in both tension and compression
Fence posts	Black locust, cedar, oak	Rot-resistant in ground contact

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Seasoning (Drying Wood)

Fresh-cut (“green”) wood is 40-60% water by weight. If you build with green wood, it will shrink, warp, crack, and loosen its joints as it dries over the following months. Seasoning removes this moisture.

Air Drying

Step 1 — Cut the tree and buck it into rough dimensions slightly larger than your final pieces — add 5-10% extra thickness and width to allow for shrinkage and warping.

Step 2 — Split logs into boards or planks as soon as possible after felling. Whole logs dry from the outside in, creating massive internal stress that causes deep cracks (called “checking” or “shakes”). Split or sawn wood dries more evenly.

Step 3 — Stack the boards in a pile with spacers (“stickers”) between each layer. Stickers should be about 2 cm thick, spaced about 30-40 cm apart, and aligned vertically from layer to layer. This allows air to circulate around every surface.

Step 4 — Elevate the stack at least 30 cm off the ground to prevent ground moisture from wicking in. Cover the top with a roof or weighted boards to keep rain off, but leave the sides open for airflow.

Step 5 — Wait. The general rule is one year of air drying per 2.5 cm (1 inch) of thickness. A 5 cm thick plank needs about 2 years. A 2.5 cm board needs about 1 year. In hot, dry climates this can be faster; in humid climates it takes longer.

Step 6 — Test dryness by weighing a sample piece weekly. When the weight stops dropping, the wood has reached equilibrium moisture content (EMC) for your climate — typically 12-15% moisture content for outdoor-air-dried wood.

Kiln Drying (Faster)

If you have a forge or kiln, you can accelerate drying:

Step 1 — Build a small enclosed chamber adjacent to your forge or kiln that captures waste heat. The chamber should be warm (40-60 degrees C) with some airflow but not direct flame.

Step 2 — Stack wood with stickers as above inside the chamber.

Step 3 — At 50-60 degrees C with good airflow, 2.5 cm boards can dry to 10-12% moisture in 2-4 weeks instead of a year. Check for cracking — if cracks appear, reduce the temperature. Drying too fast causes the outside to shrink while the inside is still wet, creating splits.

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Method 1: Green Woodworking (No Seasoning Needed)

Green woodworking is a set of techniques designed specifically for freshly felled wood. It is faster to start because you skip the seasoning wait, and green wood is much easier to cut, split, and shape than dry wood. The key is designing joints that tighten as the wood shrinks.

Splitting (Cleaving)

Splitting wood along the grain with a froe, axe, or wedges produces pieces that are far stronger than sawn boards because the grain fibers run unbroken from end to end. A sawn board cuts across many fibers; a split piece breaks between them.

Step 1 — Start with a straight-grained log, freshly felled. The log should have minimal knots in the section you want to split.

Step 2 — Stand the log on end. Place your froe blade (or axe) across the end grain at the center. Strike with a mallet to start the split.

Step 3 — Work the froe down the length of the log, levering left and right to steer the split. If the split starts running off to one side (following a grain deviation), bend the thicker half more aggressively to steer the split back to center.

Step 4 — Continue splitting halves into quarters, quarters into eighths. From an 8ths-split billet, you can shave and shape chair legs, tool handles, basket ribs, shingles, and many other parts.

The Shrinkage Advantage

The critical insight of green woodworking: wood shrinks more across the grain than along the grain. A round tenon cut from green wood will shrink in diameter as it dries, but a round mortise cut in dry wood will not. If you insert a green tenon into a dry mortise, the tenon shrinks and locks itself into the mortise permanently — no glue or fasteners needed.

This principle is used in:

• Chair making — green legs are driven into dry seats. As the legs dry, the joints become tighter than any glue joint.
• Timber framing — green pegs are driven into dry frames.
• Tool handles — green handles are fitted into dry metal heads.

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Method 2: Joinery with Hand Tools

Joinery is the art of connecting two pieces of wood without nails, screws, or metal fasteners. Good joinery distributes stress, allows for seasonal wood movement, and creates structures that last centuries.

Mortise and Tenon (The Master Joint)

The mortise and tenon is the most important joint in woodworking. A projecting tongue (tenon) fits into a rectangular hole (mortise). Used for furniture, doors, windows, timber frames, and almost every structural connection.

Step 1 — Mark the tenon. The tenon should be approximately one-third the thickness of the wood. On a 5 cm thick piece, the tenon would be about 1.5-2 cm thick. Mark the shoulder lines (where the tenon begins) all the way around the piece. Mark the tenon width and thickness on the end grain.

Step 2 — Cut the tenon. Using a saw, cut along the waste side of the tenon thickness marks, cutting down to the shoulder lines. Then cut along the shoulder lines to remove the waste. You should have a rectangular tongue projecting from the end of the piece.

Step 3 — Mark the mortise. The mortise should be exactly the same width and thickness as the tenon, and slightly deeper than the tenon is long (1-2 mm deeper provides room for excess glue and ensures the shoulder seats tightly).

Step 4 — Cut the mortise. Drill a series of overlapping holes using a brace and bit to remove most of the waste. Then clean up the walls with a chisel, working from both faces toward the center to prevent blowout. The walls should be flat and straight. Test-fit the tenon frequently — it should slide in with firm hand pressure. If you need a mallet to drive it, the fit is too tight and may split the mortise.

Step 5 — Assemble. Apply hide glue (made from boiled animal skin and hooves) to both surfaces. Insert the tenon. For extra strength, drill a hole through the assembled joint and drive a wooden peg through it (a “drawbored” or “pegged” mortise and tenon).

Dovetail Joint (For Corners)

The dovetail is the strongest corner joint. The interlocking fan-shaped “tails” and “pins” mechanically prevent the joint from pulling apart in one direction. Used for drawers, boxes, chests, and any corner connection.

Step 1 — Mark the tails on one board. The tails are the fan-shaped projections (wider at the end, narrower at the base). For hand-cut dovetails, the angle should be about 1:6 to 1:8 (for hardwood) or 1:5 (for softwood). Steeper angles are weaker; shallower angles have less mechanical advantage.

Step 2 — Cut the tails using a saw (cut on the waste side of the line). Remove waste between tails with a chisel and mallet — chop halfway from each face to prevent blowout.

Step 3 — Place the cut tail board against the end of the mating board and trace the tails onto it with a knife or sharp awl. This marks the pins.

Step 4 — Cut the pins, remove waste. Test-fit. The joint should go together with firm hand pressure and NO gaps visible. Trim with a chisel if needed.

Step 5 — Glue and assemble. Dovetails do not need pegs — the geometry holds.

Lap Joint (Simplest Structural Joint)

A lap joint removes half the thickness from each piece where they overlap. Quick, easy, reasonably strong.

Step 1 — Mark the overlap area on both pieces. Each piece gets a notch half as deep as its thickness, exactly as wide as the mating piece.

Step 2 — Saw the sides of the notch. Chisel or pare the waste flat.

Step 3 — The pieces should nest together with their surfaces flush. Glue, peg, or lash.

Used for: quick frames, scaffolding, cross-bracing, temporary structures.

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Steam Bending

Some shapes require curved wood — boat ribs, chair backs, barrel staves, wheel rims. You cannot carve a curve from straight stock without cutting across the grain (weak). Steam bending curves the wood while keeping the grain intact (strong).

Step 1 — Build a steam box: a long, narrow enclosed box (wooden planks or a hollowed-out log) with a hole at one end for steam to enter and small vent holes at the other end. Length should accommodate your longest piece.

Step 2 — Generate steam by boiling water in a covered pot with a pipe or tube leading into the steam box. A metal pot over a fire with a copper or bamboo pipe works well.

Step 3 — Place your wood piece inside the steam box. The general rule is one hour of steaming per 2.5 cm of thickness. A 2 cm thick piece needs about 45-60 minutes. Green wood bends more easily than dry wood and needs less steaming.

Step 4 — Prepare your bending form in advance — a mold or jig that matches the desired curve. This can be a log cut to shape, a series of pegs in a board, or a heavy metal strap clamped to the outside of the bend.

Step 5 — When steaming is complete, work quickly — you have about 30-60 seconds before the wood cools enough to set. Remove from the steam box, immediately place on the bending form, and clamp tightly. Bend slowly and steadily. If you hear cracking, you are bending too far or the piece was not steamed long enough.

Step 6 — Leave clamped to the form for at least 24-48 hours (longer for thick pieces). The wood will “spring back” slightly when released — overbend by about 10-15% to compensate.

Best Woods for Steam Bending

Wood	Bendability	Notes
White oak	Excellent	The classic bending wood; used for boat ribs, barrel staves
Ash	Excellent	Flexible, even-grained; good for chair backs, handles
Elm	Good	Tough; resists splitting during bending
Hickory	Good	Strong; good for tool handles needing a curve
Beech	Good	Bends well when green; tends to crack when dry
Walnut	Fair	Will bend for gentle curves only
Pine/softwoods	Poor	Tend to break rather than bend; avoid for tight curves

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Building Practical Items

A Simple Table

Step 1 — Cut four legs from 5x5 cm hardwood stock, about 75 cm long.

Step 2 — Cut four apron pieces (the horizontal pieces under the tabletop) from 2x8 cm hardwood, lengths matching your desired table dimensions (e.g., two at 60 cm, two at 90 cm).

Step 3 — Cut mortises in the tops of the legs. Cut tenons on the ends of the aprons. Each leg receives two mortises at 90 degrees to each other.

Step 4 — Cut the tabletop from boards. If you have no wide boards, edge-join narrower boards by planing the mating edges flat and gluing them together. Alternate the direction of growth rings in adjacent boards to minimize warping.

Step 5 — Assemble the legs and aprons with glue and pegs. Attach the tabletop by screwing (if screws are available) or by using wooden buttons — small L-shaped pieces that fit into a groove on the inside of the apron and screw into the underside of the top. This allows the tabletop to expand and contract with humidity changes without splitting.

A Cart or Wheelbarrow

Step 1 — Build a simple box frame from 5x10 cm hardwood for the bed, about 60 cm wide and 120 cm long.

Step 2 — For a wheelbarrow: attach two handles (2-meter-long hardwood poles, 5 cm diameter) to the back of the bed, converging to a point at the front where the wheel attaches.

Step 3 — Build the wheel: a solid disk cut from a thick hardwood plank (elm is ideal — resists splitting), about 40-50 cm diameter and 5-8 cm thick. Bore a center hole for the axle. Alternatively, build a spoked wheel — a hub (elm), spokes (oak), and a rim (ash, steam-bent or segmented).

Step 4 — The axle is a smooth, round hardwood or metal rod running through the hub. Grease the axle hole with animal fat for low friction.

Step 5 — Attach the wheel assembly to the front of the bed. Add a leg or legs at the back for stability when set down.

Boat Building (Small Craft)

A flat-bottomed punt or skiff is the simplest boat to build:

Step 1 — Build the bottom from planks — edge-join 2-3 cm thick boards to form a flat panel about 120-150 cm wide and 300-400 cm long. Seal the seams with pine pitch, oakum (tarred rope fibers hammered into the seams), or a mixture of animal fat and charcoal.

Step 2 — Bend up the sides from 1.5-2 cm thick boards. Cedar or pine works well — light and flexible. Attach the sides to the bottom with copper or iron nails, or use wooden pegs and lashing.

Step 3 — Add internal ribs (frames) cut from naturally curved branches or steam-bent oak, spaced every 30-40 cm. These give the hull its strength.

Step 4 — Add a bow transom (flat board at the front, angled) and stern transom (flat board at the back, vertical). These close the ends and give the boat its shape.

Step 5 — Seal all seams and nail holes with pine pitch or a mixture of pine tar and tallow. The boat should be launched and allowed to swell for a day — the wood absorbs water and the seams tighten.

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Japanese Carpentry (Wafuu Mokuzou)

Japanese timber-frame construction evolved over 1,300 years to build earthquake-resistant temples, shrines, and houses using zero nails, screws, or metal fasteners. Every structural connection is a precision-cut interlocking wood joint. This tradition represents the highest expression of joinery in human history and is directly applicable to post-collapse building — it requires only hand tools and wood.

Japanese Tools

Japanese woodworking tools cut on the pull stroke, opposite to Western tools. This is not a cosmetic difference — pull strokes keep the blade in tension (like a chain vs a rope), allowing thinner blades, finer cuts, and more control.

Tool	Japanese Name	Western Equivalent	Key Difference
Saw	Nokogiri (鋸)	Handsaw	Cuts on pull stroke; thinner blade (0.3-0.6 mm kerf vs 1-2 mm); less wasted wood
Plane	Kanna (鉋)	Hand plane	Pulled toward you; wooden body with blade wedged in; can produce shavings 0.01 mm thin
Chisel	Nomi (鑿)	Bench chisel	Hollow-ground back (ura); struck with a steel-ringed hammer (gennou); available in widths from 3 mm to 48 mm
Hammer	Gennou (玄能)	Mallet	Steel head with one flat face and one slightly convex face; the convex face drives without leaving edge marks
Marking gauge	Kebiki (罫引)	Marking gauge	Single or double blade scratches a line parallel to an edge; more precise than a pencil line
Ink line	Sumitsubo (墨壺)	Chalk line	Silk thread through an ink-soaked cotton reservoir; snaps a perfectly straight reference line on timber
Square	Sashigane (差金)	Framing square	L-shaped steel rule marked in sun/bu (Japanese measurements) or metric; used for layout, angles, and rafter calculations

Philosophy: Why Japanese Joinery Works Without Nails

Western framing relies on metal fasteners to hold rigid connections. Japanese framing relies on geometry — joints interlock in three dimensions so that the weight of the structure and the physics of load transfer hold everything together. Key principles:

1. Gravity does the work. Beams sit in sockets; posts sit on stones. The weight of the roof compresses joints tighter over time.
2. Flexibility, not rigidity. In an earthquake, a nailed frame resists until it snaps. A Japanese frame flexes — joints shift slightly, absorb energy, and return to position. This is why 1,300-year-old temples still stand.
3. Wood moves with wood. When two pieces of the same species are joined, they expand and contract together with humidity changes. Metal fasteners fight this movement and eventually loosen.
4. Precision is the fastener. A joint that fits perfectly needs nothing else. The surfaces bond through friction, compression, and sometimes a single wooden pin.

The 22 Joints You Need for a Post-and-Beam House

The joints below are organized by structural function. Together, they cover every connection needed to build a complete nail-free timber-frame house — foundation to ridge.

Category A: Beam Splicing Joints (Tsugite 継手)

These joints extend a beam’s length by joining two shorter timbers end-to-end. Critical when available trees are shorter than the required span.

1. Kama Tsugi (鎌継) — Goose-Neck Splice

The workhorse splice joint of Japanese carpentry. A hooked tenon slides into a matching mortise from above, then locks when the beam is loaded.

• Where used: Main floor beams (daihari), wall plates (dodai), any horizontal member that needs lengthening
• How it works: One end is cut into a tapered, hooked shape (resembling a sickle or goose neck). The mating piece has a matching cavity. The hook prevents the joint from pulling apart in tension, and the taper draws the joint tight as it seats.
• How to cut: Mark the hook profile on the end of each beam — a trapezoidal tenon with an angled shoulder that locks behind a matching ledge. The hook angle is typically 15-20 degrees. Cut with a saw to the shoulder lines, then chisel out the waste. The mating piece is cut as a mirror image. Test-fit and pare until the joint slides together with firm hand pressure and seats fully.
• Strength: Strong in compression and moderate in tension. The hook resists pulling apart. Adequate for most horizontal beams under gravity load.

2. Okkake Daisen Tsugi (追掛大栓継) — Rabbeted Oblique Splice with Peg

The strongest beam splice in the Japanese repertoire. Used where maximum tensile and shear strength is needed.

• Where used: Main ridge beams, large floor beams, any critical spanning member
• How it works: Two beams meet at a long oblique scarf (angled cut), with stepped rabbets (interlocking ledges) along the scarf face that resist sliding. A hardwood peg (daisen) is driven vertically through both halves after assembly, locking the joint.
• How to cut: Mark a diagonal scarf across the beam end at approximately 1:3 slope. Cut two or three stepped rabbets along the scarf face — each step is about 5-8 mm deep. The mating beam gets a mirror-image scarf with matching steps. Drill a vertical hole through both halves after assembly and drive a snug-fitting hardwood peg.
• Strength: Extremely strong. The oblique scarf distributes shear across a large surface area. The steps resist sliding. The peg prevents separation. This joint can carry nearly the full load of a solid beam.

3. Kanawa Tsugi (金輪継) — Metal-Ring Splice (No Metal)

Despite the name, this joint uses no metal. The name refers to its strength — “strong as a metal ring.”

• Where used: Ridge beams, tie beams, any location requiring a splice that resists both tension and twisting
• How it works: Both beam ends are cut with interlocking S-shaped profiles that hook around each other in two axes. A vertical hardwood key (shachi sen) is driven through the center to draw the joint tight.
• How to cut: Mark the S-profile on the end of each beam — this requires careful layout as the joint interlocks in three dimensions. Cut the profiles with saw and chisel. The center slot for the key is cut after the joint is assembled. Drive a tapered hardwood key to tighten.
• Strength: One of the strongest splices — resists tension, compression, shear, and twist. Difficult to cut but worth the effort for critical structural members.

4. Sao Tsugi (竿継) — Rod Splice

A simpler splice using a long tenon that passes through the mating beam.

• Where used: Secondary beams, purlins, wall plates where extreme strength is not required
• How it works: One beam end has a long tenon (about 15-20 cm). The mating beam has a matching through-mortise. The tenon passes through and is wedged from the far side.
• How to cut: Cut the tenon at one-third the beam width and about 15-20 cm long. Cut the through-mortise in the mating beam. After assembly, drive thin hardwood wedges into saw kerfs cut in the tenon end to expand it inside the mortise.
• Strength: Moderate. Good for gravity-loaded horizontal members. The wedges prevent withdrawal.

Category B: Corner and T-Joints (Shiguchi 仕口)

These join beams at angles — where posts meet beams, where beams meet at corners, and where braces connect to the frame.

5. Kama Shiguchi (鎌仕口) — Hooked Corner Joint

The corner equivalent of the kama tsugi splice.

• Where used: Where wall plates meet at building corners; where beams meet at right angles
• How it works: A hooked tenon on the end of one beam locks into a mortise in the side of the other beam. The hook prevents withdrawal.
• How to cut: Same hook profile as the kama tsugi, but the mortise is cut into the side face of the receiving beam rather than the end. The hook seats from above and locks under gravity load.
• Strength: Good for corner connections under compression. The hook provides moderate tension resistance.

6. Watari Ago (渡り腮) — Cross-Lap with Notch

A cross-halving joint with an interlocking notch for positive location.

• Where used: Where beams cross over each other (common at tie-beam/plate intersections and at hip rafter crossings)
• How it works: Each beam is notched to half its depth where they cross, so they nest together with surfaces flush. An additional small notch or ledge prevents lateral sliding.
• How to cut: Mark the width of the crossing beam on each piece. Cut to half-depth with a saw, chisel out the waste. Add a small 5-10 mm step at one edge of the notch for positive location.
• Strength: Good under gravity. Both beams retain half their cross-section at the crossing point.

7. Koshi Kake Kama Tsugi (腰掛鎌継) — Seated Goose-Neck Joint

A kama tsugi that sits on a ledge (seat) for additional bearing support.

• Where used: Where a beam needs to splice over a post or support point
• How it works: Combines the hooked tenon of the kama tsugi with a horizontal ledge that bears directly on the supporting post. The hook handles tension; the seat handles compression.
• How to cut: Cut the standard hook profile, but add a horizontal shoulder (seat) at the base that rests on the post below. The receiving beam has a matching pocket with the seat ledge.
• Strength: Very good. The seat provides large bearing area for compression loads, while the hook resists tension and uplift.

8. Hako Shiguchi (箱仕口) — Box Joint

An interlocking three-dimensional joint for connecting a beam to a post.

• Where used: Main beam-to-post connections where maximum rigidity is needed
• How it works: The beam end is shaped into a stepped, box-like tenon that fits into a matching cavity in the post. Multiple shoulders resist rotation in all directions.
• How to cut: Mark and cut a tenon with two or three steps (shoulders) on different faces. The post receives a matching cavity. Each shoulder locks against a corresponding face in the cavity. The geometry prevents racking in any direction.
• Strength: Excellent. One of the most rigid beam-to-post connections. Resists all loading directions.

9. Kabuto Ari Shiguchi (兜蟻仕口) — Helmet Dovetail Joint

A dovetailed tenon that locks a beam to a post from above.

• Where used: Tie beams connecting to corner posts; any beam-to-post connection that must resist pullout
• How it works: The beam end has a dovetail-shaped tenon that slides into a matching dovetail mortise in the post from above. The dovetail shape prevents withdrawal; gravity keeps it seated.
• How to cut: Cut the tenon with angled sides (wider at the end than at the shoulder) — the classic dovetail profile. Cut the post mortise to match, open at the top so the beam drops in from above. The dovetail angle should be about 1:5 to 1:6.
• Strength: Excellent tension resistance (the dovetail cannot pull out). Very common in traditional frames.

10. Mechigai Tsugi (目違い継) — Stub Tenon with Offset

A short tenon with an offset shoulder for quick alignment.

• Where used: Secondary beam-to-post connections, floor joist to beam connections
• How it works: A short tenon (5-8 cm) with a small offset step on the shoulder prevents the beam from sliding sideways. Simple and fast to cut.
• How to cut: Cut a standard short tenon, then add a small 5-10 mm step on one side of the shoulder face. The receiving mortise has a matching step.
• Strength: Moderate. Relies primarily on gravity and the offset for lateral resistance. Adequate for secondary members.

Category C: Post-to-Foundation and Post-to-Beam Connections

11. Daisen (大栓) — Through-Peg

Not a joint by itself, but the essential locking mechanism used in dozens of joints.

• Where used: Driven through any joint to prevent separation — beam splices, post-to-beam joints, brace connections
• How it works: A hardwood peg (typically oak, 15-24 mm diameter) is driven through a hole drilled through the assembled joint. Often the holes are slightly offset (“draw-bored”) so that driving the peg pulls the joint tight.
• How to cut: Drill the hole through one piece first, assemble the joint, then drill through the second piece with a slight offset (1-2 mm closer to the shoulder). Taper the peg end and drive it through — the offset forces the joint tight as the peg finds its way through both holes.
• Strength: Adds significant tensile and shear resistance to any joint. The draw-boring technique creates a permanent clamp force.

12. Shachi Sen (車知栓) — Wedged Key

A tapered hardwood key driven through a slot in a tenon to lock and tighten the joint.

• Where used: Post-to-sill connections, post-to-beam connections, anywhere a joint needs to be tightened after assembly or retightened after wood shrinkage
• How it works: The tenon passes through the receiving member. A slot is cut through the tenon beyond the far face. A tapered hardwood wedge is driven into this slot, expanding the tenon and locking it in place. If the joint loosens over time, the wedge is driven deeper.
• How to cut: Cut a through-tenon. After assembly, cut a slot in the exposed tenon end (perpendicular to the grain of the receiving member to avoid splitting it). Make a tapered hardwood key and drive it in.
• Strength: Very good. Allows tightening and adjustment over the life of the building.

13. Kusabi Dome (楔止め) — Wedge Lock

Wedges driven alongside or through a tenon to secure it.

• Where used: Post bases sitting on foundation stones, temporary assembly during raising, any joint that needs to be disassemblable
• How it works: The tenon is cut slightly narrower than the mortise. After insertion, wedges are driven into the gap between the tenon and the mortise wall, locking the joint. Removing the wedges allows disassembly.
• How to cut: Cut the tenon about 3-5 mm narrower than the mortise on one or both sides. Make hardwood wedges that fill the gap with a taper.
• Strength: Good. Easy to adjust and replace. Common for post bases where foundation settlement may require releveling.

14. Hozo Sashi (ほぞ差し) — Standard Post Tenon

The basic post-to-beam connection in Japanese framing.

• Where used: Every post-to-beam and post-to-sill connection in the frame
• How it works: The end of the post has a tenon (typically 1/3 the post width and 6-10 cm long) that fits into a mortise cut in the beam or sill. Secured with a draw-bored peg (daisen).
• How to cut: Mark the tenon at the post end — centered, 1/3 the post width in each direction. Saw the cheeks and shoulders. Cut the matching mortise in the beam. Drill for the peg after assembly.
• Strength: Good under compression (the post bears on the beam around the tenon). The peg handles uplift and lateral forces.

Category D: Brace Joints (Sujikai 筋交い)

Diagonal braces are critical for resisting lateral forces (wind, earthquake). These joints connect braces to the main frame.

15. Sujikai Shiguchi (筋交い仕口) — Brace-to-Post Connection

The standard way to connect a diagonal brace to a post and beam.

• Where used: Every diagonal brace in the frame (typically four or more per wall panel)
• How it works: The brace end is cut to the compound angle where it meets the post-beam intersection. A tenon on the brace end fits into a mortise at the intersection. The brace resists racking (parallelogram deformation) of the frame.
• How to cut: Measure the exact angle of the brace at each end. Cut the brace end to this angle, then cut a short tenon on the angled face. Cut a matching mortise in the post at the beam intersection, angled to receive the brace. Secure with a peg.
• Strength: Critical for lateral resistance. The brace converts lateral forces into compression and tension along its length, which the end joints transfer to the frame.

16. Kama Sujikai (鎌筋交い) — Hooked Brace Joint

A brace connection with a hooked tenon for greater pullout resistance.

• Where used: Braces in high-wind or seismic zones; critical wall panels
• How it works: The brace tenon has the same hook profile as the kama tsugi, preventing withdrawal even under tension loading (when the brace is being pulled away from the frame during racking).
• How to cut: Cut the brace end to angle, then cut the hooked tenon profile on the angled face. The mortise in the post must accommodate the hook — the brace slides in from a specific direction and locks.
• Strength: Very good. Handles both compression and tension in the brace, which sees alternating loads during earthquakes.

Category E: Floor and Roof Joints

17. Ari Otoshi (蟻落とし) — Dovetail Housing

A beam that drops into a dovetail-shaped groove in a supporting member.

• Where used: Floor joists seating into main beams; purlins seating into rafters
• How it works: The supporting beam has a dovetail-shaped groove cut across its top face. The joist end is shaped to match and drops in from above. The dovetail prevents the joist from lifting or pulling out sideways.
• How to cut: Cut the trapezoidal groove (wider at the bottom, narrower at the top) across the top of the supporting beam. Shape the joist end to the matching dovetail profile. The joist drops in from directly above.
• Strength: Good. Positive resistance to uplift and lateral movement. Fast to assemble during frame raising.

18. Koshikake Ari Tsugi (腰掛蟻継) — Seated Dovetail Splice

A dovetail splice that sits on a ledge, combining the dovetail’s pullout resistance with a bearing seat.

• Where used: Splicing purlins over a rafter; splicing floor beams over a post
• How it works: One beam end has a dovetail tenon; the other has a matching dovetail mortise with a horizontal seat that rests on the support below. The dovetail handles tension; the seat handles the gravity load.
• How to cut: Cut the dovetail tenon on one beam end. On the mating beam, cut the dovetail mortise and a horizontal bearing shoulder. The joint slides together from one end and bears on the support.
• Strength: Very good for splices over supports. Handles both gravity and lateral loads.

19. Taruki Kuchi (垂木口) — Rafter Seat Cut

The joint where a rafter sits on the wall plate (top of the wall).

• Where used: Every rafter-to-wall-plate connection in the roof
• How it works: A notch (birdsmouth) is cut in the underside of the rafter where it crosses the wall plate. The notch has a horizontal seat (bearing surface) and a vertical shoulder (plumb cut) that locks against the inner face of the wall plate.
• How to cut: Hold the rafter in position against the wall plate and mark where it contacts. Cut the seat (horizontal) and shoulder (vertical) with a saw and chisel. The seat should bear fully on the wall plate; the shoulder should fit snugly against the plate’s inner face. The rafter tail extends past the wall to form the eave overhang.
• Strength: Good. Gravity keeps the rafter seated. The shoulder resists outward thrust from roof loads.

20. Jūmonji Kumi (十文字組) — Cross-Halving for Roof Grid

A four-way intersection where two beams cross at right angles, both at the same level.

• Where used: Roof grids, ceiling grids, and any structure requiring beams crossing in two directions at the same elevation
• How it works: Each beam is notched to half its depth at the crossing. They interlock so both top surfaces are flush. Identical to the watari ago but used specifically for grid patterns.
• How to cut: Mark the width of the crossing beam on each piece. Cut to exactly half depth. Chisel the waste flat. The pieces should nest perfectly flush.
• Strength: Both beams retain half their depth at the intersection. Adequate for most roof and ceiling grids where loads are distributed.

21. Sanmai Hozo (三枚ほぞ) — Three-Way Tenon

A joint where three members converge at a single point — common at the top of a post where beams arrive from three directions.

• Where used: Corner posts where two wall beams and a roof beam all connect; T-intersections in the frame
• How it works: The post end has three tenons (or a combination of tenons and housings) that receive the three converging beams, each in its own mortise or pocket. The layout ensures each beam is positively located without interfering with the others.
• How to cut: This is the most demanding joint to lay out. Mark all three beam positions on the post end simultaneously. Allocate the post cross-section between the three connections so each has adequate bearing and tenon material. Cut each mortise/tenon set in sequence, test-fitting as you go. The key challenge is not removing so much material from the post that it is weakened.
• Strength: When properly designed, very strong — each beam is independently locked into the post. Poor layout (removing too much post material) can create a weak point.

22. Kaneori Shiguchi (矩折仕口) — Right-Angle Bend Joint

A joint that creates a rigid 90-degree connection between two horizontal members, used where a wall plate changes direction.

• Where used: Wall plates at corners; any horizontal member that must turn 90 degrees while maintaining structural continuity
• How it works: Both beam ends are cut with interlocking stepped profiles that create a rigid corner. The steps resist opening (tension on the outside of the corner) and closing (compression on the inside). A peg locks the joint.
• How to cut: Mark matching step profiles on both beam ends. Each step is typically 1/3 the beam depth. Cut with saw and chisel. The joint slides together from above. Drill and peg after assembly.
• Strength: Very good. The multiple steps create a long glue/friction surface and resist rotation. Essential for corner rigidity.

Assembling a Post-and-Beam Frame

With these 22 joints, here is how a complete house frame goes together:

Foundation — Flat stones (no concrete needed) are set at each post location and leveled. The post bases sit directly on stone, keeping wood away from ground moisture.

Sill beams (dodai) — Horizontal timbers laid on the foundation stones. Spliced with kama tsugi (#1) or okkake daisen tsugi (#2) where lengths must be joined. Corners connected with kama shiguchi (#5) or kaneori shiguchi (#22).

Posts (hashira) — Erected vertically on the sill beams. Connected with hozo sashi (#14) at base and top. Secured with daisen pegs (#11). Corner posts receive multiple beams via sanmai hozo (#21).

Wall plates (nuki/kamoi) — Horizontal beams connecting the tops of the posts. Spliced with kama tsugi (#1) over posts using koshikake kama tsugi (#7). Beam-to-post connections use kabuto ari shiguchi (#9) or hako shiguchi (#8).

Tie beams — Cross-beams connecting opposite walls for lateral stability. Connected to posts with kabuto ari shiguchi (#9). Spliced with kanawa tsugi (#3) where extreme strength is needed.

Diagonal braces — Connected with sujikai shiguchi (#15) or kama sujikai (#16) at each end. Minimum two braces per wall panel, forming an X or V pattern.

Floor joists — Dropped into main beams with ari otoshi (#17). Spliced with koshikake ari tsugi (#18) over supports.

Rafters — Seated on wall plates with taruki kuchi (#19). Roof grid intersections use jūmonji kumi (#20).

Locking — All joints secured with daisen pegs (#11), shachi sen keys (#12), or kusabi wedges (#13) as appropriate.

Raising — The frame is typically assembled in bents (2D wall frames lying on the ground), then raised into position and connected with tie beams. A community raising party is traditional — 10-20 people can raise a house frame in a single day.

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Common Mistakes

Mistake	Why It’s Dangerous	What to Do Instead
Building with green wood using standard joinery	Joints loosen as wood shrinks; structure becomes wobbly	Either season the wood first OR use green woodworking techniques (shrinkage joints)
Cutting mortises too large	Joint is sloppy and weak — no amount of glue fixes a bad fit	Cut mortises slightly undersized and pare to fit. Test frequently.
Forcing a too-tight tenon	Splits the mortise piece, often invisibly at first — fails under load later	The tenon should slide in with firm hand pressure only; pare if needed
Ignoring grain direction when chiseling	Chisel digs in and splits the wood unpredictably	Always chisel with the grain or across it, never against it. Test which direction the grain runs first.
Drying wood too fast (kiln too hot)	Surface dries and shrinks while interior is wet — deep cracks form	Dry slowly: 40-60 degrees C maximum in kiln; protect from direct sun when air-drying
Not sealing end grain	End grain dries 10-12x faster than face grain, causing end checks and splits	Seal all end grain immediately after cutting with wax, paint, pine pitch, or animal glue
Steam bending wood with knots	Knots are discontinuities in the grain; the piece breaks at the knot	Select knot-free, straight-grained stock for bending
Using the wrong species for the job	Tool handle from pine shatters; furniture from green poplar warps	Match species to application (see Wood Selection table above)

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What’s Next

Woodworking skill enables major advances:

• Structural Engineering — timber-frame buildings, bridges, dams, and waterwheels
• Printing — wooden printing presses and type blocks
• DIY Wind Turbine — wooden tower, blades, and nacelle frame
• Hydro Generator — wooden water wheels, flumes, and housings
• Boat building for trade, fishing, and exploration

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Quick Reference Card

Woodworking — At a Glance

Seasoning rule: 1 year per 2.5 cm (1 inch) of thickness. Stack with stickers. Cover top, open sides.

Green woodworking shortcut: Use fresh wood with shrinkage joints. Green tenons into dry mortises lock as they dry.

Three essential joints:

Joint	Strength	Used For	Key Rule
Mortise & Tenon	Very strong	Frames, furniture, structure	Tenon = 1/3 wood thickness; should slide in with hand pressure
Dovetail	Strongest (corners)	Boxes, drawers, chests	Angle 1:6-1:8 for hardwood, 1:5 for softwood
Lap Joint	Moderate	Quick frames, bracing	Remove exactly half the thickness from each piece

Steam bending: 1 hour per 2.5 cm thickness. Work fast (30-60 seconds to form). Overbend by 10-15%.

Best woods by use:

• Tool handles: hickory, ash
• Furniture: oak, walnut, cherry
• Boat ribs: white oak (steam-bent)
• Carving: basswood, butternut
• Rot resistance: black locust, cedar

Japanese joinery — 22 joints for a nail-free house:

Function	Joints	Key Joint
Beam splicing	Kama tsugi, Okkake daisen, Kanawa, Sao	Okkake daisen (strongest splice)
Corners/T-joints	Kama shiguchi, Watari ago, Koshikake kama, Hako, Kabuto ari, Mechigai	Kabuto ari (dovetail — resists pullout)
Post connections	Daisen peg, Shachi sen key, Kusabi wedge, Hozo sashi	Hozo sashi + Daisen (standard post-to-beam)
Braces	Sujikai shiguchi, Kama sujikai	Sujikai shiguchi (essential for earthquake resistance)
Floor/roof	Ari otoshi, Koshikake ari, Taruki kuchi, Jūmonji kumi, Sanmai hozo, Kaneori	Taruki kuchi (every rafter needs one)

Golden rule: Always cut joints slightly tight and pare to fit. You can remove wood but you cannot add it back.