Dovetail Log Cabins

Historical Background

Building with logs that were hewn with the broadaxe to have flat interior and exterior surfaces was a technique developed by and brought to this country by immigrants from Sweden and Finland. The log house was an unknown in America until about 1638, when the first and only purely Scandinavian settlement, called New Sweden, was founded along the Delaware River, at what is now Wilmington. While the Swedish brought their log-building techniques to Delaware and Maryland, the early 1700’s saw Germans and Scotch-Irish begin to settle in Pennsylvania. While these ethnic groups had a long-standing cultural background in log construction in Europe and were comfortable in its continuation here in pioneer America, it seems that only the English had no experience building with logs and instead clung to their own familiar building practice of timber framed houses sided with sawn clapboards.

The ensuing years produced a melting pot of log construction methods, as ethnic groups migrated from previously settled areas and contributed building techniques that were unique to their European heritage. Generally, historians seem to agree that the hewn, dovetailed log structure as we know it today evolved from the cultural building patterns of the Germans, Scandinavians, and Scotch-Irish. This particular style of hewn log walls with dovetail corner notches became the dominant form of log construction in the Appalachian Mountains, resulting in it commonly being referred to as the “Appalachian Dovetail.”

I’ve found it interesting to note the historical difference in terminology as it relates to log building, past and present. I’m referring to the distinction between a house and a cabin. In the past, it seems that there has long-been a negative connotation attached to the word “cabin” as it pertained to a log dwelling, with that negative implication being all but erased with the passage of time. In the pioneer landscape of early America, as opposed to modern-day vocabulary, apparently the size of a log structure was of little relevance as to how it was termed.

Historically, a log cabin was built of round logs, and often disparagingly referred to as a pole-shack, usually as temporary shelter and the first living quarters built as soon as a clearing in the forest permitted. It was hastily erected, sometimes with only the earth as a floor, with little time to be spent on craftsmanship. Oftentimes, slaves’ quarters were constructed of round logs and referred to as cabins. On occasion, in the absence of a chimney, a large opening was left in the roof to allow smoke from cooking fires to escape. By contrast, a log house was built of hewn logs, flattened on two sides (inside/outside), with carefully fitted dovetail corner notches, and was of a much higher degree of craftsmanship. It was somewhat of a status symbol for the settler, indicating that he and his family had prospered enough to rise above the crude, round-log cabin of his past. However, many dovetailed log structures were soon sided over, in an effort to emulate the refined, town-dwelling Englishman and his house of timber frame construction covered with sawn clapboards.

SPTJ Dovetail Log – System Details

1) Wall Log Quality

A superior-quality log structure begins with superior-quality material, which, when combined with appropriate and knowledgeable sawing techniques, are the initial requirements that will have the most impact on the integrity of your log structure.

I use eastern white pine wall logs, which are available at my local sawmills in lengths up to 30’. Only boxed-heart logs are used in the construction of your log cabin. This sawing method produces a log where the pith/heart, or the center of the tree remains in the center of the log along its entire length, resulting in a much more dimensionally stable wall log.

Unlike some others that incorporate small 6”x6” plantation-grown “logs” in their log structures, or thinner 6”x 12” logs that will yield only a 6” wall thickness, I use a much beefier wall log profile sawn to 8”in thickness & 12” in height. Not only is this larger wall-log more aesthetically pleasing (IMO) and more appropriate in a dovetail log structure, but the additional wood (8” log vs 6” log) surrounding the heart/pith is beneficial in a few different ways: 1) higher R-value for your log wall, &, 2) a much more dimensionally stable log due to the unstable “juvenile” wood near the heart being surrounded & protected from potential drying distortions by outer layers of more “mature” heartwood.

Although I go to great lengths to ensure quality logs go into your log structure, your local building code may mandate that wall logs be structurally graded to meet ICC 400 building standards. In this instance, I can supply wall logs and saw timbers that have been structurally graded by TPI (Timber Products Inspection) to meet ICC 400 regulations.

Once your logs arrive at my yard, great care is taken to ensure that they maintain that sawmill fresh look. All timbers are stacked and stored in a covered outdoor storage area with constant airflow to help inhibit any possible fungal growth. White pine is especially susceptible to blue stain, a fungus that attacks only the sapwood, and is present in airborne spores when dew points are high and air temperatures range between 40 and 105 degrees. Structurally, it is of no consequence, but it is visually unappealing (to most) and difficult to eradicate once it takes hold. Keeping timbers dry and with good airflow are important preventive measures in the fight against blue-stain.

2) Choice of 2 Log Profiles

Traditional/ Authentic

This log profile would be the best option (and my favorite) for those that desire the look of a traditional 1800’s dovetail log cabin, in which only the interior/exterior log faces are bandmill-sawn flat to an 8” thickness, and the top & bottom of each log retain their natural contour & roundness, giving an uneven, “live-edge” look to the chink-lines and log walls. Eastern white pine logs are selected at the sawmill that exhibit minimal taper but are still a minimum of 12” in diameter at the small end. This log size will yield a visible sawn face that averages +/- 10” from top edge to bottom edge. The bark on the top & bottom of each log is hand-peeled with a drawknife. The chink joint between log courses is built in to be 2”, but will be wavy, irregular & non-uniform, and will average 2”- 3” in height.

Rustic/Contemporary

This log profile is band-sawn on all 4 faces with sharp 90-degree corners, yielding a square-edge wall log at 8” thick x 12” in height, with a visible sawn log face (interior/exterior) at 12”. This log profile is geared more toward the modern look of dovetail log construction as popularized by the log home industry and seen in most log home magazines. Chink space in this log profile will be a uniform lateral of 2”.

3) Choice of 3 Surface Finishes

Rough-Sawn

Standard Finish on all Logs & Timbers. This term can be a bit misleading, as most folks may have the visual image of timbers sawn on a circular sawmill, which can leave a toothy, ragged appearance. Every wall log and timber in my log structures has been sawn on a bandmill, and while the effects of this sawing method are still a bit visible, it still leaves a relatively smooth finish.

Sanded Smooth- Optional

Along with providing a smooth and clean finish, belt-sanding the log faces opens up the pores in the wood, allowing much better stain/preservative penetration & adhesion when compared to a planed surface, which in effect closes the wood pores and greatly limits stain or preservative penetration.

Hand Hewn- Optional

Unlike the now-common fake “hand-hewn” look that most log home producers want you to believe is hand-hewn, (one that yields a linear series of scallops along the log that is actually produced with curved base planer), an authentic and traditional hand-hewn log has a character that simply cannot be duplicated by a power tool.

Starting with logs that average 13”-14” in diameter at the small end, the interior and exterior log faces are hewn flat with the traditional broad axe to a thickness of 8” and yield a visible hewn face that averages around 11” from rounded top to rounded bottom. Using a traditional two-axe system, first the scoring axe followed by the broadaxe, this historic, traditional method of crafting flat interior/exterior log wall “faces” will reflect the hand-cut signature marks of each of these axes in the finished log wall: slight vertical penetrations from the scoring-axe, along with smooth, sweeping undulations and slicing marks from the curvature of the broadaxe face.

4) Dovetail Corner Notching

Most log structures are defined by the distinctive and prominent style of corner notching they display. I have chosen to upgrade my building system (from half-dovetail) to a “full dovetail”, or compound dovetail notch. It is self-draining (slope of dovetail drains rainwater to exterior), and superior to the half-dovetail since the bearing surfaces are self-locking in two angled planes, a very efficient joint that truly uses gravity to its advantage as it draws the corners of the building tighter as the weight of the upper logs is applied. Inherent in dovetailed log construction is the fact that the corner notches are designed to bear 70-80% of the weight of the building, resulting in constant compression on the notches while ensuring that the joinery remains tight. Notch extensions are additional amounts of wood left on the log ends and aid in the protection of the dovetail notches and can vary according to your preference.

Preventive measures are taken to compensate for potential shrinkage-related distortion in the dovetail notches, where I hollow out the bottom notch surface, along with creating a concave hollow in the top & bottom vertical end-grain (shoulder) cuts. The goal is to prevent those mating surfaces from being pushed apart by possible raised end-grain checks once the logs are assembled. In addition, I check (and adjust if necessary) to ensure that the inside & outside edges of the bottom notch are parallel to one another and in the same level plane, and that all 4 sides of that notch are square to one another, so that even if the rough-sawn log may be a bit out-of-square, the dovetail notch will still seat square once it is set in place.

Once all dovetail corner joinery and related shoulder cuts are finished, a slotted vertical groove is cut on the inside face of each notch for placement of an Emseal gasket, (explained further on down), followed by a paraffin-based wax coating end-grain sealer that is applied to the freshly exposed ends to control end-grain checking (splits). This end-grain sealing process forces moisture to leave the timber through the long-grain surfaces (sides) and at a much slower rate than if allowed to exit the timber from its preferred and faster path of travel, which is via end-grain evaporation.

5) Chinking Components

Dovetailed log construction is not only characterized by the distinctively joined dovetail corners, but also the horizontal gap between each log course known as the chink space, one of the prominent characteristics in early American log building. Historically, this chink space was rather large & filled with all sorts of materials ranging from moss to wood chips, to cow manure, and then plastered over with various mixtures of clay, lime, straw or horsehair. Materials and solutions evolved over the years to include wire lath nailed to the logs and coated with a lime/sand/cement/clay mix. I have a couple of great “old-fashioned” recipes of that for those that may be interested.

Today, there are many synthetic, flexible chinking compounds on the market designed specifically for log homes to accommodate the natural log movement. In the Traditional/Authentic log profile I “build-in” a 1” chink space in my structures, but due to the natural and uneven rounded shape of the top/bottom of the wall logs, the faces of the visible chink areas will vary in size, but average around 3”. In the Rustic/Contemporary model, the 2” chink space is a consistent and uniform lateral. There will be 3 aspects to chinking your log structure: insulation placed into these lateral spaces, a bond-breaker or backer material over that, and an interior/exterior topical chinking sealant. All 3 components are supplied with your log cabin package. They are described below.

A) Chink Space Insulation

After much research into the many options and opinions regarding the best insulation for the chink spaces, as well the insulation for your roof, I’ve come to the conclusion that natural sheep wool far outperforms all other products on the market in virtually every critical category. I was searching for an all-natural, chemical-free insulation product that fit in well with an all-natural wood structure, and ISOLENA Sheep Wool, carried in the U.S by Scep Sheep Wool www.scepwool.com met all the criteria that I was looking for. They use 100% pure virgin sheep wool with no synthetic fillers and no artificial materials such as recycled carpet fibers that contain plastics and/or petrochemicals. Their wool is protected from insect infestation by their biocide-free & patented Ionic Protect® process, a permanent & irreversible plasma ion treatment of the wool fibers developed by ISOLENA (details on their website). In addition to the high thermal performance of their product, I’ve chosen their “Klemmfilz” line of insulation for the chinking laterals, as this product boasts some very impressive acoustic properties with a sound-absorption rate of 85%, assuring that these spaces are not only well-insulated, but virtually soundproof as well.

Sheep wool has natural insulating properties with millions of tiny air pockets, has a rated R-value of approx. 3.5 per inch of material thickness, and is also flame retardant. In addition to these naturally occurring characteristics, sheep wool fibers are composed of a-keratin, the same general type found in human hair & nails, and also found in animal feathers, horns, & hooves. Keratin also explains sheep wools crimped structural nature and elasticity, where sheep wool can “spring-back” and retain its original shape within the chink joint. In the unlikely event that moisture does penetrate the chink joint, keratin’s structure in sheep wool explains its unique ability to absorb and release up to 30%-40% of its own weight in moisture, this due to a natural outer layer that repels water while an inner structure can absorb air-borne moisture without feeling wet. This inherent characteristic does not compromise sheep wool’s natural insulating qualities, as is common to both fiberglass and cellulose. And unlike fiberglass, natural sheep wool handles nicely on-site, no masks are needed, and there are no respiratory or skin related irritations associated with its use. Yes, it is a bit more expensive than rockwool or fiberglass, but I strongly feel that the positive attributes in natural sheep wool far outweigh the cost differential when compared to a lesser product. The insulation will come to you pre-cut into ready-to-install 6” strips @ 2.36” high x 6” wide x 20’ long. The 2.36” height will allow for a snug, slight compression-fit within the 2” chink laterals. And from what the folks at www.scepwool.com tell me, I am the only log builder in the U.S. that includes 100% natural, chemical-free sheep wool insulation from ISOLENA in their log cabin packages. Based on the size of your structure and the volume of the laterals, all the required sheep wool is included in your log cabin package.

B) Chink Space Bond Breaker

After the sheep wool insulation is applied in the chink joint, a bond breaker (Grip Strip from PermaChink) is applied next, both inside and outside. This functions exactly as its name implies: to break any type of adhesion, or bond, with the topical synthetic chinking. The goal being to allow the flexible chinking compound to bond to the upper and lower logs only, and not to any material behind it. This bond breaker is a trapezoidal shaped, chemically inert closed-cell polyethylene that is shaped to fit between log courses to form a flat surface for the application of the synthetic chinking compound. This makes it easier to maintain a consistent thickness of sealant across the chink space, reducing the amount of sealant required and improving the sealant’s performance. It contributes a combined R-value of R-4 when applied to both inside/outside chink spaces. In addition to the R-value of the sheep wool insulation, you will have an R-value of R-11 in the chink space laterals. Due to the natural log shape and rounded log edges in the Traditional/Authentic log profile, the visible chink face area will vary between 1”-3”, so Grip Strip bond breaker in the 3” size is included. Some cutting and fitting of this product will be required to accommodate the irregular chink joint. The Rustic/Contemporary log profile has uniform 2” chink laterals, so the 2” Grip Strip bond breaker will be included.

C) Chink Space Interior/Exterior Sealant

The final step in the chinking process is the application of the exterior sealant. This is an acrylic material that looks and applies like traditional mortar, but unlike mortar it is textured, flexible & stretches to accommodate log movement, adding the final seal to chinking the laterals. This sealant comes in a variety of colors and is included in your log cabin package in the color of your choice. PermaChink’s website has detailed information concerning the application of all their products. Best practice is to start the chinking process on the exterior: install the Grip Strip bond-breaker & exterior sealant on all laterals first, then move to the interior and install the sheep wool insulation, bond breaker and then the interior sealant.

6) Preventing Air & Water Infiltration

Unlike timber frame construction where the layers of exterior skin protect against the elements, a log wall acts as both the structural frame and the first/last line of defense against air and water intrusion. Therefore, key elements in this regard begin with a quality building system, followed by a sound and effective plan to prevent air and water infiltration. This can possibly be an issue at corner notches due to radial shrinkage, where the logs will shrink in diameter but not longitudinally, therefore creating a slight gap at the vertical shoulders. Strategic placement of an air-blocking gasket along with caulking the notch perimeter (all mentioned below) are the remedies for solving these issues.

Despite the most diligent efforts, there still remains the ever-slight possibility that wind-driven rain may penetrate the corner joinery at some time in the life of your log cabin, as the constant expansion/contraction cycles common to wooden structures may create small openings in even the most well-crafted and tight dovetail corner notches. The application of a high-quality caulk around the entire dovetail notch perimeter (Energy Seal by PermaChink) that will also expand & contract, designed exclusively for log structures & included in your log package will act as the water seal.

Addressing the issue of air infiltration is the employment of an open-cell foam gasket by Emseal Log Home Tape. This high-performance sealant has been impregnated with acrylic-modified asphalt, and is placed in a pre-cut shallow, slotted groove (in which it can expand) at the vertical interfaces of all dovetail corner joinery. Emseal gaskets are included in your log cabin package.

7) Wall Alignment Pins

Keeping the log walls in a rigid vertical plane and assisting in combating load forces generated by the roof and other sources is the use of beefy 1- 1⁄4” x 22” hardwood wall alignment pins. These are octagonal in shape and are sawn from air-dried black locust and placed in pre-drilled holes staggered @ 4’-6’ intervals along the length of all walls & perform several key functions: they interlock multiple courses of logs, they assist in keeping the walls in a proper vertical plane, and increase the rigidity of the log wall, while the octagonal shape ensures that the logs can shrink around the pin and settle with no vertical impediment, as only the corners of the octagonal pins will make contact with the hole perimeter. I recommend coating the pins with a block of paraffin wax to facilitate their entry and to reduce friction. In the top three courses of eave walls where rafters will bear, I use thicker 1-1⁄2” x 24” black locust alignment pins spaced @ 3’ intervals. These larger pins will assist in countering any possible rafter thrust imparted onto the eave walls. You may see other log builders using rebar in their log walls. Unfortunately, this will shorten the life of your log structure due to the incompatibility of materials, which is multiplied in an outdoor environment, with the rebar creating a condensation surface within the logs.

Also assisting in wall alignment and settling is the placement of air-dried 2” x 5” load-bearing wall support blocking at all window & door openings and along the log perimeter wall in sill-to-eave stacks, keeping roof/floor loads in a continuous vertical path. All alignment pins and wall blocking are supplied in your log cabin package.

8) Window & Door Jambs

Precise, solidly built & functional accommodations must be in place to facilitate the natural settling of the wall logs around windows & doors, while also ensuring proper load distribution around these openings. My system here at SPTJ utilizes a stout, robust “T-spline” assembly of structurally graded, stable, kiln-dried material: a double 2×8 side jamb composition fastened together with both structural screws and construction adhesive.

These side jambs will have 5” long vertical, sliding settlement slots to accommodate washer-headed lag screws, one slot on each side (two per log) of a 2×4 spline that is fastened into a centered, recessed 1-1/2” x 1⁄2” routed groove on the inside face of the double 2×8 side jambs, again using both structural screws and construction adhesive. The adhesive here serves two purposes: first, an added barrier to possible air infiltration, and secondly, it strengthens the assembly. Jambs are pre-drilled to accept the screws and to pull the 2×4 spline tight into the jamb recess, a seemingly minor issue but critical, nonetheless.

A two-gasket system is used in this T-spline assembly. Both gaskets are a 1” wax-saturated open cell gasket made by either Emseal or Denarco and adhered to the 2×8 jamb and function as sealants between the inside face of the jamb and the log ends. One is applied on the inside of the spline and acts as a vapor barrier. It prevents household moisture from entering the assembly. The second gasket is applied on the outside of the spline and prevents any possible rain infiltration into the assembly. This outer gasket is very important where windows or doors are exposed to wind driven rain.

The 2×8 side-jambs and the attached 2×4 spline assembly then fit into pre-cut 4” deep by 1- 1⁄2” wide keyways cut in the log ends, allowing the wall logs freedom of downward movement by sliding down the length of the imbedded 2×4 spline. Upon installation, best practice would include coating the 2×4 splines with paraffin wax to facilitate this natural settling.

A related item of utmost importance that is too detailed to address here: It is critical that you or your GC take the correct measures to properly flash windows and doors, including head, sill, and jamb flashing on both sides of windows and doors. Improper window installation and flashing installation (or lack of it) is one of the main culprits leading to log wall rot, along with base course logs too close to close to the ground.

The complete T-spline jamb assembly will come to you fully assembled & gasketed, with detailed installation instructions and drawings in your assembly manual.

9) Allowances for Log Settling

When mentioning the word “settling”, it refers to the vertical reduction in height of horizontally laid logs in a wall system due to the combination of cross-grain shrinkage in a log and the compaction of the logs from the weight of the wall and roof system. Green logs will shrink and will do so more in cross-section than along their length, although eastern white pine is one of the most dimensionally stable of the softwoods and has some of the lowest shrinkage rates. ILBA Log Building Standards state that green logs (in chinked dovetail) must be allowed to settle approx. 4% of total wall height. That doesn’t mean the log walls will settle that much, but those accommodations must be accounted for. A variety of factors affect the total amount of settlement in a log wall, including moisture content of the logs, wood species, density of the wood, and roof loads. This height reduction usually occurs slowly and over a 5-year period in a heated building. Effective methods to counter any potential problems with logs settling include adequate cut outs in header logs above door and window openings, Nortek settling jacks (which can be hidden by finish trim) under all vertical timbers, and the employment of proper window/door jambs to accommodate the inevitable downward movement. Settling is only a problem when it is not accounted for in a log structure.

10) Borate Treatment of Wall Logs

Inhibiting fungal growth and insect larvae in timbers with a borate-based wood preservative is an effective method to help control decay-causing fungi. Borate-based wood preservatives are derived from naturally occurring, water-soluble mineral salts that are mined in California. They are highly effective as a wood preservative in preventing fungal decay and are deadly to most wood-boring insects (termites, old house borers, carpenter ants, etc.), but are non-toxic to people, pets, and the environment. Some of you may be familiar with the old-time laundry detergent still found on grocery store shelves, 20 Mule Team Borax, in which borates are the primary ingredient. Borate salts are odorless, have no effect on the color of the wood, are compatible with most exterior stains (check with manufacturer), will not interfere with chink-joint adhesion, and are non-corrosive to metal fasteners. When applied to “green” logs/timbers, the water-soluble borate solution uses the woods’ own high moisture content as a transport medium to naturally penetrate and diffuse deep within the log or timber. In both of the log profiles offered by SPTJ, the wall logs come to me with their large inside/outside faces sawn down to the insect-resistant heartwood, with the Traditional/Authentic profile retaining their natural sapwood on the two adjacent 8” top/bottom faces, while the Rustic/Contemporary profile will have some sapwood removed in the sawing process. This sapwood is susceptible to rot and harboring insect larvae. To protect the logs from both of these natural enemies, I cut a 2” deep chainsaw kerf along the length of every log on both the top & bottom and saturate the kerf with a borate solution. This channel in the log’s sapwood allows the solution to permeate and diffuse throughout the log, giving your logs the insect-killing/rot-protection that they deserve while they are in my care. This chainsaw kerf also serves a secondary purpose as it provides a nice, hidden relief cut to encourage checking pressure to be relieved at the kerf’s location as opposed to the visible faces of the logs. I then fill this kerf with lengths of 1⁄4” gasketing to prevent rainwater from collecting in it during storage and shipping.

11) Electrical Wiring

All wall logs are vertically pre-drilled with 11⁄4” holes at various points to run the wires. The open chink space can also be used for wire and box placement. Other options include a built-up baseboard that provides an electrical chase behind the baseboard and conventionally framed interior partition walls and floor system. Wiring up to loft areas can be laid in a pre-routed channel in the top surface of a rafter or beam and before the decking is nailed on. Your chosen electrician will have the best solutions for your given circumstances. Be sure to check with local building codes for acceptable installation details concerning the wiring of your log structure. Also, there are many videos and articles online concerning wiring a log home.

Timber Frame Roof Options

When thinking about a timber frame roof system to complement your log structure, inherent in that choice is the structural impact it will make on the log walls below. Each of the timber framing roof options listed below address roof load-paths by different means, but all of them share 2 common goals: 1) eliminating rafter thrust before it reaches the top plate log, keeping in mind that it increases exponentially as roof pitch is lowered, and 2) preventing mid-span rafter sag. Many variables will determine which roof framing system is structurally suitable for your particular situation, with the appropriate one being designed by the engineers at Fire Tower Engineered Timber www.ftet.com & matched with the unique features that your project presents.

Common Rafters with Collar Ties

This rustic and complimentary roof system is an ideal fit for log structures typically 18’ & smaller in width. Rafter pairs are secured at the peak by a traditional mortise & tenon joint & joined by the structurally correct placement of collar ties. In keeping with tradition, stepped-lapped rafter joinery locates and seats the rafters on the plate logs. Included in this roof system package are GRK structural screws in the proper length & quantity, securing the rafters to top plate log while addressing uplift resistance by providing the required hold-down capacity. Also included are LSTA30 Simpson Straps, fastened across each rafter pair where they meet at the peak, keeping tension at that location and as further insurance against roof loads bearing on the top plate logs.

Common Rafters with Posted/Braced Structural Ridge Beam

Adding a loft with adequate walkable headroom or increasing structure width beyond a certain point may necessitate a more robust roof framing system than a simple Common Rafter arrangement to handle the newly introduced forces at play. This roof system is composed of a large ridge beam at the peak, which is supported by posts directing vertical loads down to the foundation, and augmented laterally by diagonal bracing, with common rafters notched, strapped & hung from the ridge beam. Depending on structure length, this framing system will typically have at least one post in the first floor living area. Included in this roof system package are GRK structural screws in the proper length & quantity, securing the rafters to top plate log and ridge beam, addressing uplift resistance by providing the required hold-down capacity. Also included are LSTA30 Simpson Straps, fastened across each rafter pair where they meet at the peak, keeping tension at that location and as further insurance against roof loads bearing on the top plate logs.

Principal Rafters/Purlins

This roof framing system features fewer but larger rafter pairs connected by horizontal purlins running parallel with the ridge line, each half-lapped over the middle rafter (secured with structural screw) and then dovetailed into the gable-end rafters. Each rafter pair is supported at midspan by matching vertical posts. At rafter peak, they are joined by a traditional pegged mortise & tenon joint, while the historically preferred step-lapped joint seats each rafter on the top plate logs. This framing scheme was very common in the New England area in the 1600-1800 era. Depending on structure length, this framing system will typically have at least one post in the first floor living area.

Queen Posts/Purlin Plates/Common Rafters

This timber composition is often seen in barn frames of the past and would be applicable to larger-width structures. It is composed of two purlin plates running parallel with the ridge line, one above each eave wall supporting a series of common rafters at their mid-span, with the purlin timbers themselves being supported by an H-bent configuration of two opposing vertical (queen) posts, tied at or near their tops by a diagonally braced and horizontal tie beam. Depending on structure length, this framing system will typically have at least one post in the first floor living area.

Kingpost Truss

When done artfully & correctly, this is a beautiful and structural marvel of timber arrangement that allows a clear-span (no interior posts) in the living area below by the complex interaction of each timber as they function together to mitigate undesirable loads paths. The design is comprised of a single vertical kingpost, two diagonal struts, a continuous horizontal tie beam, and a rafter pair meeting at the top of the kingpost. In a proper design, the kingpost does not bear on the tie beam but is actually in tension as it is holding up the tie beam at mid span, supplemented by the upward pawling action of the rafter pairs at the head of the kingpost. The two diagonal struts are received at the base of the kingpost and extend up to support each rafter at mid span. I’ve been blessed in my career to have done 4 different projects that employed multiple kingpost trusses. A challenging and enjoyable experience.

Timber Frame Loft System

When adding a loft, an additional 3 log courses, or knee walls, will be necessary to accommodate the needed walkable headroom in the loft. These 3 added courses add not only wall logs and loft joists, but also much additional labor in the form of debarking the additional logs (if Traditional / Authentic), corner notches, alignment pins, & the extensive joinery in the supporting tie beam system below and joists. A 12/12 roof pitch is typically employed to maximize usable loft headroom.

The framing is comprised of a tie beam spanning the width of the structure and joined into the eave wall logs with a housed dovetail joint. The tie beam is supported at mid-span by a braced and pegged post. The loft joists span from the tie beam to the gable wall and feature dovetail joinery. A Nortek screw jack is included for the central, first floor loft post. Beefy 1-1⁄2”x 24” octagonal locust wall alignment pins are included & penetrate the added knee-wall log courses on the eave walls adding another layer of structural security and ensuring lateral wall stability.

WESTERN RED CEDAR Timber Frame Porch System

Incorporating a rot-resistant species such as western red cedar for the exposed post and brace timbers is a new, upgraded feature that not only adds a level of beauty to your porch, but also natural protection for the exposed, weather-vulnerable posts & braces. The post/brace interface can be prone to retaining rain/snow which can also seep into the brace mortise and eventually lead to rot in species that are not decay-resistant. The combination of pre-drilled “weep holes” in the brace mortice bottoms on the posts to facilitate rainwater drainage and the natural decay-resistance of red cedar are effective remedies ensuring the longevity of your timber frame porch. I’ve chosen only the exposed timbers (posts & braces) to be red cedar, as the white pine top plate and rafters are protected under cover. Your choice of rot-resistant pegs (white oak or cherry) fastens the mortise & tenon joinery together. Nortek screw jacks (included) under all posts allow for settling to match that of the log structure. GRK structural screws (included) in proper length & quantity in securing rafters, both to the log wall and the porch plate, providing hold-down capacity while supplementing the stepped-lapped rafter/plate timber joinery.

Standard Components in Every Log Wall Package

When comparing SPTJ to others, please review and take note of the exceptional features listed below that are included in your log cabin package, with each one indicative of the custom workmanship and the high level of detail & care that translates to a superior, high-end product.

  • Boxed-heart, eastern white pine wall logs (8” thick x 12” high) pre-drilled for alignment pins and electrical wiring. Numbered & directionally labeled according to their orientation within the structure. Compound dovetail notches lock the corners together in two angled planes.
  • Anchorseal end grain sealer on all dovetail notches & log ends at windows & doors.
  • Top & bottom of logs chainsaw kerfed 2” deep for check-control and Borate treatment saturation.
  • Kerf filled with 1⁄4” poly rope to block any rainwater during storage and shipment.
  • Emseal gaskets in pre-cut channel (hidden) in all dovetail corner notches, prevents air infiltration.
  • Choice of 2 log profiles
  • Choice of 3 surface finishes
  • Completely assembled and gasketed double 2×8 side jambs with sliding settling slots & T-spline system for window and door openings to accommodate settling. Keyways pre-cut on all log end openings @ windows/doors to accept T-spline jamb.
  • Octagonal wall alignment pins (1-1⁄4”x 22” locust) penetrate multiple courses to insure lateral wall stability, interlocking each course of logs.
  • Wall blocking in proper size & blocking flats cut on top/bottom of all wall logs.
  • Logs banded for shipment in 2,000 lb lifts with nylon banding that will not stain logs.
  • Every log in every lift separated both vertically and horizontally by 1” stickers, facilitating air flow through the stack and preventing “blue-stain”.
  • Loading of all project material, along with all necessary 4x4x8’ blocking when loading your project onto truck/trailer. You will need this blocking when material is unloaded at your building site.
  • Project-specific assembly manual
  • Hand Drawings on 17×22 paper of all 4 log walls with elevations & dimensions. Your local building dept may require professional drawings. I work with several designers that specialize in dovetail log design that can produce a CAD plan set that will satisfy your building dept.

All Necessary Chinking Materials Included in your Log Cabin Package

  • ISOLENA Klemmfilz sheep wool insulation for chink spaces, pre-cut into ready-to-install 2.36” thick x 6” wide x random length strips.
  • GripStrip bond-breaker in proper size and quantities.
  • ENERGY SEAL log-specific caulk for dovetail notch exterior, in your choice of color, prevents rain infiltration.
  • PermaChink chinking sealant (5 gal pails) in proper quantities in your choice of color.

Pricing Structure – Effective as of October 2026

I’ve separated the different timber frame options that compose a traditional log structure in order to offer you the financial flexibility to choose what fits your budget the best, while not obligating you to choose an “all-in-one” log cabin package that includes these timber frame elements that may not suit you. For example, some may simply want the Basic “Log Walls Only” package with the high-quality of log wall construction and the features & products that I include as standard and choose a roof system of conventional 2x framing or trusses, while others may not need or want a loft or porch. But the addition of any or all of these timber frame elements will certainly enhance the enjoyment, character and value of your log cabin. The cabin sizes priced below are simply templates to give you an idea on cost. I can build whatever size log structure that fits your lifestyle.

The 18’ x 24’ Log Cabin

  • Basic- Log Walls Only– Traditional Log Profile – $22,755
    • 8 full log courses
    • 9’-2” plate height
    • Standard features as listed above
  • Basic – Log Walls Only– Rustic Log Profile – $20,585
    • 8 full log courses
    • 9’-2” plate height
    • Standard features as listed above

Add- Timber Frame Common Rafter Roof System – $8,015

  • Must be P.E. approved
  • 6 x 8 rafters
  • 6 x 8 collar ties
  • White Oak, Cherry, or Ash pegs.

Add- Timber Frame Loft – Rustic $13,600 / Traditional $15,030

  • Additional 3 log courses = 11 full log courses
  • 12’-8” plate height
  • 8 x 12 Tie Beam dovetailed into log walls
  • 8 x 8 Center Post with 4 x 6 Braces
  • White oak, Cherry, or Ash pegs
  • 6 x 8 joists dovetailed into tie beam and gable wall log

Add- Timber Frame Western Red Cedar Porch – $8,824

  • 8’ W x 23’L
  • 6 x 6 EWP Rafters
  • 6 x 6 Western Red Cedar Posts
  • 4 x 6 Western Red Cedar Braces
  • 6 x 8 EWP Top Plate
  • Choice of Rot-Resistant Pegs (Cherry or White Oak)

The 24’ x 28’ Log Cabin

  • Basic- Log Walls Only– Traditional Log Profile- $26,375
    • 8 full log courses
    • 9’-2” plate height
    • Standard features as listed above
  • Basic – Log Walls Only– Rustic Log Profile – $23,175
    • 8 full log courses
    • 9’-2” plate height
    • Standard features as listed above

Add- Timber Frame Ridge Beam Roof System with Rafters- $9,469

  • Must be P.E. approved
  • 8 x 14 Ridge Beam
  • 6 x 9 Rafters
  • 8 x 8 Posts
  • White Oak, Cherry, or Ash pegs.

Add- Timber Frame Loft – Rustic $14,495 / Traditional $17,505

  • Additional 3 log courses = 11 full log courses
  • 12’-8” plate height
  • 10 x 12 Tie Beam dovetailed into log walls
  • 10 x 10 Center Post with 4 x 6 Braces
  • White oak, Cherry, or Ash pegs
  • 6 x 9 joists dovetailed into tie beam and gable wall log

Add- Timber Frame Western Red Cedar Porch – $9,186

  • 8’ W x 27’L
  • 6 x 6 EWP Rafters
  • 6 x 6 Western Red Cedar Posts
  • 4 x 6 Western Red Cedar Braces
  • 6 x 8 EWP Top Plate
  • Choice of Rot-Resistant Pegs (Cherry or White Oak)

Items of Interest

1) Optional Compression Spring /Through-bolt Fastening System

As I am always looking for ways to improve my building systems, that quest involved much research into whether to add a through-bolt system as a standard feature to my dovetail log builds. But after consulting with a few structural engineers with expertise in log construction, it was determined that due to the small, stout, and relatively simply nature of my builds (standard 4-cornered designs, log walls not exceeding 40’ in length, no mid-wall splices, no big expanses of glass) and combined with the compressive weight of the massive wall logs & the inherent self-locking & self-tightening qualities of the compound dovetail notch, that the addition of a compression-spring thru bolt system as a standard feature was structurally and economically unnecessary. While a thru-bolt system does have its place in a log-on-log system where much smaller “logs” are used, or more complex or larger log structures, I will be offering it as an optional feature available to you, my intent being to not obligate you to pay significantly more for a structural element that may not make your log home better for it. However, should your local building code mandate this type of mechanical fastening system within the log walls, or maybe you simply want that extra piece of mind that this system offers, I can arrange to have a system that will be designed & engineered specifically for the many variables unique to your structure and its location. It will include specifics on thru-bolt rod diameter, compression spring size, wire diameter, spring rate & preload values, bearing plate sizes, proper rod spacing based on your window/door locations, settlement allowance, and a precise adjustment schedule.

2) Thermal Performance of Log Walls

When comparing the insulation qualities of a log wall vs. standard frame construction, the common R-value used to measure energy-efficiency cannot and should not be applied here. Eastern white pine, the species most commonly used in log construction, has one of the highest rated R-values at R-1.3 per inch of thickness. This yields an R-value of a little over R-10 for the 8” thick wall. Not too bad in itself but compare this to the standard 6” stick framed wall packed with fiberglass which carries an R-19 rating, and the log wall lags a bit behind when using that standard of measure. But log walls march to a different drummer and draw their energy-efficiency not so much from an insulation standpoint but from the thermal mass of the logs themselves. Thermal mass refers to the ability of a material to store heat and then slowly re-radiate that heat (a time-lag of around 8-12 hours) when the surrounding air temperature falls below that of the material. A concrete driveway on a sunny, hot summer day is an example of thermal mass because it absorbs, holds, and re-radiates heat well. Walking barefoot at noon on that driveway may be intolerable but take that same barefoot stroll after dark and you will still feel the warmth under your feet. Log walls perform in this same manner. They act as a thermal storage system and delay the impact of outside air on inside air. In the winter, the log walls retain heat that is internally generated and re-radiate that heat, allowing the interior surface of your log walls to remain warm to the touch. Conversely, in the summer, they also absorb and re-radiate the heat of the outdoors, resulting in an interior that retains the cool indoor air and a wall that will feel cool to the touch. Some may view the 2” chink space as a potential weak link in the thermal performance of the log walls, but this concern is eliminated with the addition of the high R-value of the ISOLENA sheep wool.

3) Exterior Design Recommendations

Some exterior design features that may be common and appropriate in stud-frame construction should not be employed when building a log structure. In my opinion, the two biggest design flaws in log construction are foundations that permit the base course logs to be too close to the ground, and uncovered decks that are attached to the house. Both of these errors in design allow rain splash-back to hit the lower course logs, and/or melting snow to pile up against those bottom logs, creating a situation where mold, and then eventually rot become a certainty. Water is the enemy of log homes. Dry logs do not deteriorate. Initially, rain splash-back will present itself as a maintenance issue, causing black mold stains on the lower 2-3 courses. This continued exposure eventually results in the base course log or logs rotting and needing to be replaced. Needless to say, this is a much different scenario than with a simple clapboard-sided building, where replacing a few pieces of siding would remedy the situation.

Another very important aspect in a properly designed log structure in terms of its longevity is sufficient roof overhang. A wrap-around porch would be the ideal design feature, as it offers full protection against sun and rain for the wall logs and corner notches. A downside to the wrap-around is that it does tend to limit the amount of natural light entering the ome, resulting in a somewhat darker interior. A well-designed log structure that features effective preventive-maintenance strategies incorporated within its exterior design are: foundations that place the base course log at least 16” above grade (20” is better), wide roof overhangs at the gable ends (24”-36”), and/or covered or wrap-around porches.

Keep all shrubbery at least 3’ from log walls, as all ground plantings are prone to holding moisture-laden air, especially on the north side of buildings, and tend to cause mold and contribute to the decay process.

Avoid the tendency to stockpile firewood against log walls. The combination of wind-blown rain and leaves that will get lodged in between the pile and log wall is a recipe for mold and also offers a convenient pathway for insects to enter your home.

Not to be ignored when addressing the topic of water and log structures is the potential damage that water from inside the house can do. High-moisture areas like kitchens and baths generate water vapor that can seep into loft- joist pockets in the wall logs. What happens over time is the loft joist ends will shrink a bit in diameter, while the wall log (and the mortise the joist sits in) will show virtually no shrinkage (longitudinal) along its length. This shrinkage differential will result in small gaps appearing at the joist end and wall log interface. In the winter, the loft-joist ends, being notched in and located closer to the colder exterior surface of the wall log, will attract warm, moist air through these gaps that will seek to condense on the colder joist ends. Hidden frost can form on these joist end notches, which will eventually melt. Repeated wet/dry cycles over the years create conditions for decay, not only on the joists, but also in the wall log mortises that they sit in. Any shrinkage gaps around joist-ends where moist interior air can get to should be filled with backer rod and caulked.

4) Wood Finishes for Logs & Interior Timbers

Assuming that you have taken the proper steps involving the exterior design of your log cabin, you will still have log walls that will be exposed to a variety of destructive natural elements. Log walls will need periodic maintenance for the life of the structure, an undeniable fact with not just log structures, but with all exposed exterior wood. But by choosing a high-quality exterior stain and applying it according to manufacturer’s specs, you can lengthen the time span between applications. Log structures need a superior product that has been specifically developed and tested for its unique requirements, and one of the most important decisions you will make once construction is completed is the quality of the finish/stain you will apply to the exterior of the logs. Don’t be tempted to purchase a stain/preservative from the big-box stores. There are many companies that manufacture excellent wood finishes that cater exclusively to the log home industry, with www.permachink.com, www.sashco.com, www.sansin.com, and www.sikkens.com among those that have been around awhile and have informative web sites and produce high-quality products. Permachink was one of the first companies on the scene over 20 years ago that offered maintenance products aimed at the log home industry. Their web site offers valuable tips on the do’s & don’ts concerning exterior maintenance of log walls, as well as a vast array of products that will keep your log structure looking great for many years. Take your time and research the different companies out there and the quality of their products.