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Leaks at log home butt joint Types of Splines & Gaskets on Solid & Milled Log Homes

Here we the types of sealants, chinking, splines or gaskets used during the construction of both traditional rough cut logs and modern milled log or solid log houses.

This series of articles provides information on the inspection and diagnosis of damage to new and older log homes and includes description of log house and log siding insulation values and alternatives, and also a description of the characteristics of slab-sided log homes as well as all other types of log home construction.

We include illustrations of log structures from several very different areas and climates in both the United States and Norway. Our page top photo shows a modern kit log home constructed in New York State.

For modern kit and factory-sourced log structures we include details of common construction and building defects that cause water and air leaks and ultimately rot damage and we point to key problem areas that need to be inspected carefully when buying or maintaining a log home.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Types of Log Wall Spline & Gasket Sealing Methods

On both traditional rough-cut log buildings and on modern kit logs and milled log structures there are many designs for sealing the interfacing logs as well as sealing at windows, doors, and building eaves. Here we provide photos and text of basic log sealing methods, both traditional chinking and weather stripping and modern splines, gaskets, and caulks.

Our page top photo shows a modern milled log that uses a double raised rib or "spline" that mates itno a groove milled into the bottom surface of each log above. Gaskets (or in some cases caulk) are used on top of each spline (or on occasion along side them) in this design.

Traditional Log Walls Used Chinking not Splines nor Gaskets

Green cabin Two Harbors Interior © Daniel Friedman at InspectApedia.com

As our photo (above left) shows, a traditional log house, built from individually-cut logs, may have included cutting or sawing the mating surfaces of horizontally (usually) or vertically (less common) placed logs against one another to obtain a flat surface. Other homes were constructed with fully-round logs and no planing of the mating surfaces.

Vertical log wall home © Daniel Friedman at InspectApedia.com

But in all cases, to avoid terrible drafts and water leaks, a variety of log wall chinking methods were used between the logs of a log house:

Single-Splined Log Mating Surfaces

Simple spline log wall © Daniel Friedman at InspectApedia.com

Our photo (left) shows a simple single-spline log constructed building built probably after 1970.

The top and bottom of each log was milled flat and a single rabbet groove cut into the log.

The groove was intended to carry a single wooden spline between logs to stop draft. You'll notice that no chinking is used between logs in walls that use a spline design.

Omission of log splines or log gaskets specified by the log manufacturer will lead to infiltration losses, drafts, possibly water leaks from wind-blown rain, and higher heating bills.

Double Splines Between Log Mating Surfaces

Logs in more recent modern kit homes are mated along their horizontal surfaces either by one or more splines that are set into grooves cut into the mating surfaces of logs as they are stacked, or the upper surface of the lower log may one or more raised ridges that set into grooves cut into the bottom surface of the log being placed on top of the lower unit.

Cross section of a modern D-shaped solid log used in log homes

Our photo shows a typical "D" profile log in cross-section at a building corner. The checking you see in this log end is normal and is not a structural concern.

But notice how the left-hand large check just below the middle of the log slopes down to the log interior ? This opening will collect water and can lead to long term log rot or frost damage.

Log kit specifications usually call for either caulk applied atop the raised spline, or as in the case of the log we show here, along the two raised splines.

Other log companies call for a special gasket to be placed either atop the splines or along side them to assure that these joints will be weather tight.

Caulk or Gaskets Used at Multi-Splined Log Mating Surfaces in a Log House Wall

Double splined log with caulk (C) Merrimac Homes

Most milled-log manufacturers now use a more complex spline design, often with two raised splines on the upper surface of each log that are intended to mate with two rabbets cut into the bottom of the log above (see our photos just above). (Photos courtesy of Merrimac Log Homes)

Log gaskets (C) Merrimac Log Homes

Gaskets are placed on or between or in front and behind each of these mating spline/groove seals, or on top of a single wide spline (photo above-right) or the manufacture may specify use of a bead of special caulk on top of each spline (photo at far left).

In Merrimanc's photo (above-left) you can see the required bead of caulk set atop each spline as the log is being placed. Don't let too much time elapse between caulk placement and log placement or the caulk may be dry and may not seal well.

We advise against simply using generic caulks in these locations.

Luckily, and probably because this is a common error, there are special products that can be used to remedy leaks in log walls. If inspection or if cold, windy weather reveals air infiltration leaks, call your inspector or log manufacturer for suggestions for special log chinking, caulks, or other log home crack or leak sealants.


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