Leaks at log home butt joint Cause, Effect, & Dealing with Log Shrinkage in Solid or Milled Log Homes

  • SHRINKAGE & HEIGHT CHANGES, LOG WALL - CONTENTS: Guide to Diagnosing & Repairing Leaks & Other Problems on Modern Kit Log Homes
    • Guide to Identifying, Diagnosing & Repairing Older & Antique Log Homes
    • Log caulk, spline, gasket, and coating product guide for log houses
    • Log checking, cracking, shrinkage, & Leaks in log houses and log siding
    • Window & Door Installation Details for Log Homes can prevent later leaks & Damage
  • POST a QUESTION or READ FAQs about shrinkage in log home walls, logs, and other structural components

This article explains the cause, effect, and cure for shrinkage in log homes: log home log shrinkage, cracks, checking: how to determine which log cracks are harmless, which cause leaks into the structure (or rot or insect damage), and how to properly find and seal cracks or other problems caused by log or beam shrinkage.

Shrinkage in solid logs used to construct both antique and modern log houses produces some special challenges to the builders of those homes. Shrinkage produces not only checking (large cracks that are normal and are not necessarily a problem) but also an actual reduction in log diameter which can, in extreme cases, mean that a wall may shrink in height by an inch or more after construction. A tall log wall like the one in our page to photo may shrink two inches over its height during the first year or year and a half after the building has been closed-in and heat turned on.

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An Owner-Builder's Guide to Shrinkage & Shrinkage Cracks In Log Home Walls

Log splits or checks in a log homeLog homes will shrink considerably in wall height as the logs dry during the first one or two years after construction.

This is so even in factory cut "dry" logs which may have absorbed moisture in transit or on site, and it is even more true if the logs used in construction were "air dried" or were used while still "green".

The more moisture that was present in logs at the time of construction of a log home, the greater the amount of shrinkage that will occur in overall wall height, and the larger and more extensive will be the checking cracks that occur in log walls.

[Photo courtesy Arlene Puentes. Click to enlarge any image]

Even factory-milled kiln-dried logs may vary in moisture, or they may pick up moisture during transport and storage at the building site. Construction details such as the means of fastening each log course in place and the framing and construction of windows and doors need to take into account this natural movement and log shrinkage that occurs especially over the first 18 months after construction of a new log home.

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.

Log Checking or Splitting - Are Log or Beam Splits A Structural Concern?

Log checking, long horizontal splits in the log surfaces, will appear on both inside and outside surfaces of log walls and may vary considerably in width (hairline to 1/2") and length (a few inches to several feet).

Checks in logs (or other large timbers) are rarely a structural concern, but they may become a leak or rot problem.

Checks are only a cosmetic concern unless they are taking in water and therefore risking leaks into the building interior or causing rot or inviting insect damage, as we discuss below

See Log Checking or Splitting for additional details about splits and checks in log buildings.

Interior Condensation and Moisture During Log Home Curing

Log cabin condensation on window (C) Daniel Friedman

Considerable moisture may be released during the first year or two after construction of a log home, after the home is totally enclosed and central heating / air conditioning have been installed.

Our photo (left) shows frozen condensation on a log cabin window overlooking Lake Superior (Two Harbors, MN).

Log moisture content is easy to measure using any of several types of moisture meter. Log moisture measurements can help determine whether the condensation seen in a log home is coming from the logs as they cure, from leaks, or from some other moisture source.

We discuss log moisture content, green logs, air dried and kiln dried logs, and avoiding log splitting problems on log houses at Log Checking or Splitting. These same factors affect the level of indoor condensation in a building in the first year or two after construction has been completed and the building is fully enclosed.

Log Wall Height Changes During Log Curing

Log walls can shrink up to several inches in overall height during curing, depending on how much moisture was in the logs when the home was constructed. There may also be some seasonal changes in the height of a log wall as ambient moisture varies and as heating or air conditioning are used in the home.

Modern log homes use construction details and log fasteners designed to permit this log shrinkage movement without damage to other rigid building components like windows, doors, plumbing, electrical wiring, and fixtures.


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