Historical Background
Heavy Timber Carpentry is an ancient building craft dating back thousands of years, a system of building the skeletal framework of structures using large wooden posts (vertical), beams (horizontal) and braces (diagonal), fastened to each other with mortise & tenon joinery and locked in place with wooden pegs.
This method of construction was brought to this country in the 1600’s by the European immigrants of England, Germany, Holland, and France. Each ethnic group brought with them their own building traditions, which included individual preferences for timber species, joinery, and framing styles.
In the New World that these settlers created, and prior to the Civil War and Industrial Revolution, virtually all barn, house, & church frames were built in this manner. Back then it wasn’t referred to as “timber framing”, it was simply “carpentry”; house & barn builders fell under the same skillset and were referred to as “housewrights”, while the bridge builders that crafted the many beautiful timber trussed covered bridges were “bridgewrights”. Or universally, these skilled craftsmen were labeled as “joiners”.
In many early American timber frames (and as odd as it may sound), joiners indeed used a Square Peg (in round holes) at specific connections within the timber frame, in securing such members as: lapped half-dovetail braces, purlins to principal rafters, and particularly in the attachment of rafters to the top plate. In Dutch barns, square pegs have been found in the thick oak planks of the threshing floor, attaching them to the timber floor system below. In log cabins of the past, the pioneers fashioned Square Pegs when framing their windows to secure their window bucks to the openings in the log walls. The incompatibility of the square peg into the round hole, combined with the wedging effect it provided, made for an unusual but very strong fastening technique. This square peg/round-hole connection has held up well for hundreds of years.
My Timber Frame Philosophy
I very often see the terms “timber frame” & “post & beam” used interchangeably to refer to the same building methodologies as it applies to heavy timber carpentry. I’d like to take this moment to clarify my take on this misconception as it relates to my approach to Timber Framing. The only similarity these two concepts share is the use of timbers in the forming of the skeletal framework. The critical difference lies in the method of timber attachment to one another.
True Timber Framing employs traditional, historically proven, mortise & tenon, pegged, wood-to-wood joinery. Post & Beam relies on metal (knife plates, bolted-on gusset plates) to secure flush-cut timbers that are devoid of any type of mating joinery to one another. It is a quicker, cheaper, watered down version of timber framing. Unfortunately, many may not be aware they are paying for one, and getting the other.
To be fair, post & beam construction, with the inclusion of steel as a joinery method, does allow engineers to meet building codes more efficiently when presented with a timbered structure, since pegged mortise & tenon joinery can present some engineering challenges in the quantifying of the structural capacity of such joinery, whereas the performance metrics of steel can be readily defined and applied.
I have a strong belief in traditional timber frame designs, based on historical precedents, in which the timbers that tie a structure together are layered, bottom to top, and running in alternate directions. Each layer tied the building in a direction opposite to adjoining layers.
For instance, a timbered floor system links the structure securely across its width and length at its base. Continuous tie beams provide tying strength transversely, and continuous top plates tie the building longitudinally once more. These overlapping layers determine the strength of a traditional timber frame, relying on compression joinery & leaving the pegs as a supplement to the system and therefore not entirely dependent on them.
Many of today’s modern timber frame designs eliminate the continuous top plate, considered the most important element in traditional timber frame structures. These non-traditional designs use full cross-section bents, where rafters tenon into the tops of posts, and the bents are connected with short-tenoned members of one bay’s length. Pegs hold these bents together, causing the braces to put many joints in tension, instead of relying on the hold-down capacity of the top plate as was done in traditional timber frame designs.
My choice of joinery layout on timbers is accomplished using a traditional system believed to have been developed here in America around 1800, called Square Rule Layout. This system replaced the older and more time-consuming method, which was brought here from Europe and called Scribe Rule Layout, in which each timber was laid out on the ground and scribed, or custom fit to its mate.
In Square Rule Layout, small reductions, or housings are cut at joint locations, thereby creating a slightly smaller, perfect inner timber that is square, straight, and uniform in size, thus overcoming any organic or milling irregularities and allowing the pre-cutting of timber joinery and bypassing the repeated assembly/disassembly process that was inherent in the Scribe Rule technique.
The pegs that lock the timber joints together are all individually hand made. I lay out a grid on straight-grained billets of white oak, and pegs are hand-split using the same method and tools as our forefathers once did: a large wooden club and froe, followed by shaping on the shaving horse with the drawknife, with additional smoothing from the block plane. This process yields a very strong peg that is straight-grained from tip to tip, with no grain run-out that is common in saw peg stock.
As was traditional, pegs are octagonal in shape and tapered along their length, which facilitates the draw-boring process, where the tenon peg hole is offset from the mortise peg hole, so that when the peg is driven into these misaligned holes, it will draw the joint tight and hold it tight throughout the timber-drying process. In barn frames of the past, protruding peg lengths were left intact and were not sawn flush with interior timber faces, which proved to be quite handy in the hanging of various small farm implements.
Design Considerations
In timber frame construction, timber size is largely determined by the frame design, the load placed on each individual timber, the species and grade of each timber, and the design (strength) values allocated to that particular species.
For example, eastern white pine has relatively low design values when compared to, say, northern red oak, which will in turn necessitate slightly larger timbers in your frame. White pine has many desirable characteristics that make it one of the most suitable species to be used in heavy timber construction. It tends to remain dimensionally stable, has a relatively low rate of shrinkage, a beautiful rustic quality, much less prone to surface checks and “ring-shake” than hemlock, a nice strength-to-weight ratio, and it is much lower in cost than most hardwoods.
All-in-all, it comes pretty close to being the perfect timber framing species. Also, for the handcrafter practicing his trade with hand-tools, EWP has a very workable texture that is a pleasure to work with. But the choice of wood species for your timber frame is entirely dependent on your preferences. After working with many different wood species and sawmills over the years, I can get virtually any wood species that you like.
Another issue related to structure size is the fact that only continuous-length tie beams, which span the width of traditional timber frames and were standard in barn and house frames of the past, are incorporated within the frameworks that I build.
These tie-beams and their joinery must be able to withstand the tensile stresses that can be generated within a frame, and it is my belief that a continuous length tie-beam, as opposed to one that is spliced and/or splined (and often seen in modern frames), will stand up to these structural forces the best.
There are less-critical forces acting on timbers that run parallel with the ridge line (top plates), therefore scarfed (spliced) timbers can be, and traditionally were, used in these locations to lengthen a structure when desired.
Frame Pre-assembly & Raising
The process of raising your timber frame usually occurs in two phases. First is the onsite pre-assembly of the timber framework, where each timber within a bent (cross frame) is laid out, assembled to its mate and pegged, stacked and lying flat on the deck and ready to be raised in proper sequence.
This process can take anywhere from 1-3 days depending upon the complexity of the frame and how many helping hands are available. This pre-assembly sequence of the frame cross-sections must match up with the planned raising sequence, as the first bent to be assembled & lying on the deck will be the last one to be raised, and the last bent stacked on the deck will be the first one to be raised.
On raising day, the bents are lifted into their vertical positions by crane, boom truck, or other forms of mechanical assistance.
Once they are securely & vertically braced, connecting girts, braces, top plates and rafters are then lifted into position, fitted and pegged.
Since I am a one-man business with no crew or machinery, I do not offer on-site structure installation. A much more logical and economic choice is where the client gathers up an able-bodied crew and procures mechanical assistance from a local source.
However, I will have prepared for you a very detailed, project-specific assembly manual that will easily guide you through the pre-assembly process and then the actual raising day, along with a list of tools and equipment that you will need, with every timber labeled (N/S/E/W) according to its orientation within the frame, and identified by name relative to its placement in the structure.
For local projects, I can be onsite (if desired) and help with pre-assembly and then in an advisory capacity on raising day. For long-distance projects, I always make myself available via phone or email for consultation.
Standard Features Included in Every Timber Frame Package:
- Any timber species of your choice.
- Timbers 4×8 & larger are sawn as “boxed heart, end-to-end”, ensuring dimensional stability.
- Standard finish is bandmill/roughsawn. Optional planed smooth/fine-sanded, which opens wood pores, facilitates stain penetration & absorption.
- Timber frame packages shipped as “ready-to-assemble” on your foundation.
- All necessary, project-specific hardware included.
- All timber joinery rooted in historical precedent, featuring pegged, mortise & tenon, wood-to-wood joinery & crafted with traditional hand-tools.
- All mortise & tenon joints are “draw-bored”: Historically traditional technique where peg holes are intentionally misaligned, forcing the peg to wind its way through the joint, holding joinery tight even thru the drying process. No come-a-longs needed in the pre-assembly.
- Pegs are white oak, ash, or cherry. Octagonal & tapered to facilitate the draw-bore and historically standard.
- GRK structural screws secure rafters to top plate, providing hold-down capacity while supplementing the stepped-lapped rafter/plate timber joinery.
- Anchorseal end grain sealer on all joinery. Prevents end-checks, helps ensure joint integrity.
- Timbers banded in 2,000 lifts with no-stain, nylon banding, edge protectors, and separated both horizontally and vertically with 1” stickers to facilitate air flow within the stacks.
- 6 page, project-specific assembly manual.