Timber Framing

Part of Woodworking

Timber framing is the art of building structures from large wooden beams joined with mortise-and-tenon joints, secured by wooden pegs — no nails, no screws, no metal hardware. This method has built homes, barns, churches, and bridges for thousands of years across every continent. A well-built timber frame can stand for centuries.

History and Advantages

Timber framing predates metal fasteners. The oldest known timber-framed structures are over 7,000 years old. The method persists because it works exceptionally well.

Advantages over stud framing:

• No hardware required: Every connection is wood-to-wood, secured with wooden pegs
• Massive strength: Large timbers resist fire, wind, and seismic loads better than small studs
• Longevity: Properly built frames last 200-500+ years
• Repairable: Individual timbers can be replaced without dismantling the structure
• Beautiful: The exposed frame is the finished interior — no need to hide it behind drywall

The trade-off: Timber framing requires more skill, more planning, and larger trees than stud framing. Each joint is custom-cut. There is no room for error in layout.

Planning a Frame

Terminology

Term	Meaning
Bent	A cross-sectional frame — two posts and a beam (or truss) spanning between them
Bay	The space between two bents
Sill	The lowest horizontal timber, sitting on the foundation
Post	A vertical timber, standing on the sill
Girt	A horizontal timber connecting posts at mid-height
Plate	The top horizontal timber, connecting post tops along the wall
Tie beam	A horizontal timber connecting opposing posts at the top (part of a bent)
Brace	A diagonal timber that prevents racking (lateral collapse)
Purlin	A horizontal timber connecting bents in the roof plane
Rafter	An angled timber from plate to ridge, carrying the roof surface

Design Process

1. Determine the building footprint: Length and width
2. Set the bay spacing: Typically 8-12 feet between bents, depending on roof load and timber availability
3. Design the bent: Each bent is a 2D frame — two posts, a tie beam across the top, and braces. Add a truss if the span requires it
4. Plan the connections: Every intersection needs a specific joint type
5. Draw it full-scale: A “lofting floor” — a large flat surface where you snap chalk lines showing every timber in its actual position

Start Simple

Your first frame should be a single bay — two bents connected by plates, girts, and purlins. This could be a small shed, workshop, or storage building. Master the process on a small structure before attempting a house.

Wood Selection and Preparation

Species

Use what grows locally. Excellent framing species include:

• Oak (white or red): The classic. Strong, durable, heavy
• Douglas fir: Straight, strong, lighter than oak
• Eastern white pine: Easy to work, lighter, good for small frames
• Hemlock: Strong, economical, widely available historically
• Larch/tamarack: Naturally rot-resistant, excellent for sills

Timber Sizing

Rough guidelines for a residential-scale frame:

Member	Typical Size
Sills	8” x 8” or 6” x 8”
Posts	6” x 6” to 8” x 8”
Tie beams	6” x 8” to 8” x 10”
Girts	6” x 6” to 6” x 8”
Plates	6” x 6” to 6” x 8”
Braces	4” x 4” to 4” x 6”
Purlins	4” x 6” to 6” x 6”
Rafters	4” x 6” to 6” x 8”

Preparation

1. Hew or mill timbers square: From round logs, use a broadaxe or saw to create flat, square faces
2. Check for twist: Sight along each timber’s length. A twisted timber will produce misaligned joints
3. Mark a reference face: Choose the best face of each timber and mark it consistently (traditionally, the face that will be visible). All measurements are taken from this reference face
4. Season or use green: Timbers can be framed green (they will shrink but the joints tighten as they do) or air-dried. Green framing is traditional and acceptable for most species

Checking for Twist

Lay two short, straight sticks across the timber — one at each end. Sight across the tops of both sticks. If they are parallel, the timber is true. If one is canted relative to the other, the timber has twist. A twisted timber must be hewn or planed to correct before layout.

The Layout Process

Layout is the most critical phase. Every measurement must be precise. Errors compound — a 1/4” mistake in layout becomes a joint that does not fit.

Rule Joints From One Face

All measurements on a given timber are taken from its reference face and reference edge. This ensures that even if the timber is not perfectly square, all joints align.

Snap Lines

1. Snap a chalk line along the reference face of the timber, marking the center line
2. Mark the position of every joint along this line — measure from one end (the “starting end”) consistently
3. Transfer joint positions to all four faces using a square

Marking Joints

1. At each joint location, mark the exact mortise or tenon with a mortise gauge and knife lines
2. Mark the depth of every cut
3. Label every joint with its position code — “Post 1, north face, girt mortise” or similar
4. Double-check every measurement before cutting

Marriage Marks

Marriage marks are a traditional numbering system scratched or chiseled into the wood at each joint. They identify which pieces connect and in what orientation.

Common systems:

• Roman numerals: I, II, III, IV at each joint pair
• Chisel ticks: Parallel lines — one tick on the first bent, two on the second, etc.
• Combination: Bent number + joint position (e.g., “III-north-top”)

Marriage marks are essential because after all joints are cut, the frame is disassembled for transport to the building site. Without marks, you are solving a massive puzzle.

Joint Cutting Sequence

Cut joints in this order for best accuracy:

1. Sills first: They establish the footprint
2. Posts: Cut tenons at the bottom (to fit sill mortises), mortises for girts and braces in the middle, tenons at the top (to fit plate or tie beam)
3. Tie beams: Mortises for post tenons, mortises for king post or braces
4. Girts and plates: Tenons at each end to fit post mortises
5. Braces: Tenons at each end, cut to the correct angle
6. Purlins and rafters: Last, after the main frame joints are complete

Primary Joints Used

Connection	Joint Type
Post to sill	Mortise and tenon (through or blind)
Girt to post	Mortise and tenon
Brace to post	Angled mortise and tenon
Tie beam to post	Mortise and tenon or half-dovetail
Rafter to plate	Birdsmouth + peg
Purlin to rafter/bent	Mortise and tenon or housed
Scarf (lengthening)	Halved scarf with pegs

Test-Fit Every Joint

After cutting each joint, assemble it dry. The tenon should slide in with firm hand pressure. If you need a mallet, the joint is too tight and may split the mortise during raising. If it wobbles, add a thin shim and recut for the next attempt.

Assembly Order

Pre-Assembly (On the Ground)

1. Lay out all timbers for one bent on a flat surface
2. Assemble the entire bent flat on the ground — posts, tie beam, braces, all pegged
3. Verify all joints fit, all members are in the correct position, and the bent is square (measure diagonals — they should be equal)
4. Disassemble if needed for transport, or leave assembled for raising

Raising Sequence

1. Set the sills on the foundation, level and square
2. Raise the first bent: Using pike poles and rope, lift the assembled bent from horizontal to vertical. A crew of 8-20 people depending on the size
3. Brace temporarily: Nail or peg diagonal braces from the bent to stakes in the ground. The bent must stand plumb (vertical) on its own
4. Raise the second bent: Same process
5. Connect with plates and girts: Lift the horizontal members into position and peg them into the post mortises. This locks the two bents together
6. Install purlins: These connect the bents in the roof plane
7. Install braces: Diagonal braces in the wall planes prevent racking
8. Remove temporary braces: Only after permanent braces are installed

Safety During Raising

A timber bent weighs hundreds to thousands of pounds. It can kill instantly if it falls. Never stand under a bent during raising. Keep the rope team on the opposite side from the pike pole team. Have a designated caller who directs all movements. Stop if anything feels wrong.

Community Raising Tradition

Historically, barn and house raisings were community events. The building owner prepared the timbers over months, then invited neighbors for a single day of raising. Food and drink were provided. The entire frame could go up in a day with enough hands.

This tradition exists because:

• Heavy timbers require many people to lift
• The raising sequence must happen quickly (temporary braces are not stable long-term)
• Skilled direction from the lead framer keeps everyone safe
• It builds community bonds and reciprocal obligation

Plan your raising for a day with no wind. Brief all participants on the sequence beforehand. Assign specific roles — pike pole, rope, peg driver, brace installer.

Wall Systems

A timber frame is a skeleton. The walls between the posts can be filled with various materials:

System	Description	Insulation	Difficulty
Wattle and daub	Woven sticks plastered with clay/straw mix	Low	Easy
Straw bale	Stacked straw bales between posts	Excellent	Easy
Cob	Monolithic clay/sand/straw mix	Good	Moderate
Board and batten	Vertical boards with narrow strips covering gaps	Low	Easy
Brick or stone	Masonry infill between timbers	Moderate	Hard
SIP panels	Structural insulated panels (modern)	Excellent	Easy

The frame carries all structural loads. The infill is just a weather barrier. This means you can change or repair wall systems without affecting the frame.

Foundation Connections

The frame must connect to the foundation securely.

Stone Foundation

Set the sill timbers on top of a stone foundation wall. Place a moisture barrier (birch bark, tar paper, or slate) between the stone and wood. The sill sits by gravity — its own weight and the weight of the frame above hold it in place. In high-wind areas, drill through the sill into the top course of stone and drive a wooden peg or iron drift pin.

Post-in-Ground

The simplest method — the posts extend below ground level, buried 3-4 feet deep. This eliminates the sill but exposes the post to ground moisture and rot. Use naturally rot-resistant species (locust, cedar, larch) and char the buried portion.

Pier Foundation

Individual stone or concrete piers under each post. The sill spans between piers. This keeps all wood well above the ground.

Adding Floors and Lofts

For multi-story frames:

1. Floor beams (summers): Heavy horizontal timbers spanning between girts or sills, carrying the floor load
2. Joists: Smaller timbers spanning between summers, supporting the floor boards
3. Mortise joists into the girt: Each joist end has a tenon that fits into a mortise in the girt
4. Floor boards: Laid across the joists, tongue-and-groove or ship-lap

A loft (partial upper floor) uses the same method but covers only part of the bay, leaving the remaining space open to the roof.

Maintenance and Repair

Timber frames require periodic inspection and occasional repair:

Annual Inspection

• Check all visible joints for gaps or movement
• Look for water staining — indicates a leak that will cause rot
• Inspect sills and any wood near the ground for soft spots (rot)
• Check braces for looseness — retighten pegs if needed

Common Repairs

• Rotted sill section: Jack up the frame, cut out the bad section, scarf in new timber
• Loose joint: Drive a new, slightly oversized peg. If the mortise is enlarged, wedge the tenon
• Cracked timber: If the crack does not pass through a joint, it is cosmetic. If it does, sister a new timber alongside and peg through both
• Insect damage: Identify and eliminate the insects first. If structural loss exceeds 25% of the timber cross-section, replace the member

Keep Water Out

The number one enemy of a timber frame is water. Ensure the roof sheds water well away from the walls, the foundation keeps the sills above splash-back height, and there are no places where water can pool against wood. A dry timber frame will last indefinitely.

Timber Framing — At a Glance

Timber framing builds structures from large beams connected with mortise-and-tenon joints secured by wooden pegs — no metal hardware. Plan the frame as a series of bents (cross-sectional frames) connected by plates, girts, and purlins. Select straight, untwisted timbers and lay out all joints from a consistent reference face. Cut joints in sequence (sills, posts, tie beams, girts, braces), test-fit every one dry, and mark with marriage marks for reassembly. Raise bents with a crew using pike poles and rope, brace temporarily, then connect with horizontal members. Fill walls with wattle-and-daub, straw bale, cob, or boards. Inspect annually, keep water away from wood, and the frame will stand for generations.