Log Building Systems
Corner Systems
Corner systems vary in complexity and many manufacturers offer more than one style of corner. Corner type can affect final house cost by affecting both the labor and time required to construct log walls. Subtle variations in corners result from different manufacturers’ methods of dealing with fastening and sealing corners. However, most log home corners fall into four basic categories.
Butt & Pass
Butt & Pass corners are the simplest and most widely used in log homes. Using this system, one log of a corner pair butts against the other log of the pair. Thesecond log usually passes beyond the corner to overhang outside the corner of the house. Butt & pass logs alternate in successive log courses, creating a distinct pattern of alternating overhanging logs on the corner. The pattern is a desirable feature of many log home buyers because it instantly identifies the house as a log home.
Butt & pass corners are often modified to create a stronger or better sealed joint. For example, notches may be cut in the pass log into which fits a tongue cut in the end of the butt log (mortis & tennon). While these may increase strength or weather tightness of the corner, a basic butt and pass joint is still strong enough and can be made tight enough to handle the stresses imposed by the log system.
Dovetail
Dovetail joints require precision cutting machinery or a skilled hand-crafter. The joints are designed so that settling and normal log movement act to strengthen rather than loosen the joint. In a dovetail, the two logs that form the corners are each notched in a modified “V.” The “V” holds the corner together and any movement in the log or settling tends to drive the logs tighter together. Dovetail joints are characteristic of many handcrafted houses and are reminiscent of the early log homes built throughout the Appalachian Mountains.
Saddle-notch
Saddle notches often secure corners in a variety of log profiles. The basic joint is made by cutting a notch into one or both logs of a corner pair. One log fits into the notch in the other or, if both logs are notched, the two are interlocked. Like dovetails, saddle notches are cut using precision machinery or in the case of handcrafters, by hand. Saddle notches simplify corner construction and may reduce labor costs. Like butt and pass corners, saddle-notched corners produce a distinctive appearance. A fully notched corner can have solid, rather than alternating overhangs on both sides of each corner. Overhangs may be cut in decorative patterns.
Post & Sill
Post & sill construction is distinguished by the presence of vertical posts at corners and periodically along walls. Actually not just a corner system, it represents a different method of log wall assembly. Usually posts are slotted allowing insertion of a tongue milled into the end of the log. As a result, post and sill houses are similar to timber frame homes. As logs settle, they simply slide down the slots in the posts. The frame does not settle.
Log Type
A variety of wood species are used for the logs that make up a log home. Manufacturers and prospective log home owners invest much energy in defending one species or another. In fact, the preservatives, modern sealants and insect repellents that are part of modern log homes make differences in wood species less significant to the structural integrity of the house. Specific woods, however, have characteristics that may appeal to a particular buyer or offer a particular look. For example, oak has a very rich grain that appeals to some people; cedar offers a distinctive color and aroma that attracts others.
Selection of wood species affects the finished house costs. Pine and oak are usually less
expensive than cedar. Cypress also carries a higher price tag. In addition to solid log wall systems, an increasing number of manufacturers are offering “super-insulated” log systems. These originated as a means of meeting stringent energy code requirements in some areas. Super insulated systems consist of half-logs or log siding covering a core of insulated framing or structural insulated panels, both inside and out. The appearance is identical to a solid log house with manufacturers even including full log corners to maintain a traditional log home “look.” Interior construction is simplified because such homes do not require special features to control log settling. These homes offer a broader market appeal by combining many of the most desirable features of a log home with some of the positive features of a conventional home.
Fasteners
Logs can be secured in the wall using a variety of fasteners. Three of the most common
fasteners include spikes, lag screws, and through-bolts. Some manufacturers pre-drill the
logs for the fasteners used to ensure proper placement, spacing, and vertical alignment.
All three factors can affect the settlement of the log wall system and the integrity of its weather tight seals. Each log home manufacturer should provide details on the properutilization of fasteners in their log wall system.
Sealing Systems
Each manufacturer includes a sealing system designed to prevent air and water infiltration at joints. A variety of materials are used and new sealants frequently appear on the market. Sealants may be solid foam or compressible material such as butyl rubber, liquid foam, and caulk. Some systems use splines and adhesives instead of, or in addition to, foam and caulk sealants. Solid foams are supplied in rolls or sheets and are designed to be compressed between logs. They may be adhesive although some are not. Liquid foams are supplied in cans or bottles and are injected into holes or grooves. They are designed to expand, sealing spaces around them. Caulk is designed to be injected into joints and is often used to seal log home exteriors and interiors. Depending on a variety of factors, reapplying caulk may be a part of routine maintenance of a log home. It is important to properly maintain a log home to prolong its life and beauty.
