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Checking or splits in solid logs used to construct both antique and modern log houses worry homeowners even though usually they do not present a structural problem. But checks in structural wood beams as well as checks and splits in logs used to construct log homes can result in water or air leaks into the building. Also see ROT, TIMBER FRAME for a discussion of the cause and prevention of log checking during log or timber dryout, and for a case study of rot in timber frame construction.

Our page top photo shows the author's precision probing device exploring checking (also called splitting or cracking) of a structural wood beam in a pre-1900 home that had been moved to a new concrete block foundation. As solid wood beams and logs cure, shrinkage produces not only checking (large cracks that are normal and are not necessarily a problem) but also an actual reduction in log or beam diameter.

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.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

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

Log 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.

Usually the crack in the wood beam or solid log radiates from the outer surface of the log towards the log center; it is not common for a log or beam split or crack (or checking) caused by the drying process to pass beyond the center of a log or beam. However more severe splits and cracks can occur in a wood structural member, even passing through its full diameter, due to structural loading or damage.

Log Checking or Splitting - Are Log or Beam Splits A Structural Concern on a Milled Log House?

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). (Photo courtesy Arlene Puentes.)

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

What Problems Might Be Caused by Checking and Splits in Log Walls

Checks and splits in the upper radius of log walls on the wall exterior are of more concern than checks and splits in the lower half of these walls.

Checks even in the lower radius of log walls - that is just below the center or outward-most face of the curved log face may also be a problem if they occur in a position and shape to send water running down the log wall into the log interior. Rain or melting snow sending water into these checks can cause these problems:

• Air and water leaks into the log building interior, especially where the checks lead water to a poorly-sealed window or door frame. In particular, where a window or door has not been properly sealed by splines, gaskets, or other means in a log wall, and where checks in the log conduct water towards the window opening, water and even air infiltration leaks are likely on that log building. An indoor view of this leaky window on a new log home can be seen at Spline Gaps & Gasket Omissions.
• Rot damage or insect damage and even a severe mold contamination problem can follow cosmetic damage and drafty conditions if a leak into any building cavity remains unattended for long enough.

So as our photo (above left) shows, even a structurally harmless shrinkage crack or check in a log wall can lead to an interior leak if the window was not properly constructed. This particular log check reached to the center of the log and bypassed the caulk that the builder had placed around the window frame on the log wall exterior.

Checks in the lower radius of the curved outer face of a log wall and checks in weather-protected location are unlikely to cause damage and are only cosmetic.

Tips for Avoiding Leaks at Splits & Checks in Log House Walls

• If the building is to be constructed using milled logs or a log home kit be sure to follow the log manufacturer's instructions for receiving, storing, and protecting logs from weather at the site.
• Find out ahead of time if your log home logs are specified by their manufacturer as "green" or "kiln dried" or "sticker dried" - as the log moisture content will vary considerably depending on these conditions. Framing procedures of any building absolutely need to take into account the condition of the framing lumber, beams, or logs. Don't frame or build with green lumber or green logs assuming they won't move and change considerably in diameter.
• Measure the moisture of structural beams or logs for a log wall for a log home at the time the lumber is delivered as well as before use. Discuss any surprises or changes in the moisture level with your supplier before using the material.
• Protect the logs or wood beams from weather during construction as well. A framed-up log wall that is left exposed to the weather will absorb moisture even if it arrived "dry" at the building site.
• Be sure to install all of the splines, gaskets, caulk, T-jambs, or other sealing mechanisms required between logs in a log home wall as well as at all window and door openings.
• When checking appears on logs after construction this is a normal event. But if checks in the upper radius of logs on a log home can trap rain, leading it inside the log crack into the building at a window or door, you may need to seal these openings with a sealant approved by your log supplier.

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

LOG HOME ENERGY EFFICIENCY
LOG HOME GUIDE
  Antique & Old Log Cabins
  Cracks, Checking or Splitting Beams & Log Homes
  Condensation &Moisture in Log Homes
  Energy Efficiency of Log Homes
  Leak Diagnosis & Cure for Log Houses
  Log Wall Height Changes
  R-Values of Log Homes
  Sealants, Caulks, & Coatings for Log Homes
  Shrinkage In Log Home Walls
  Slab Log Cabin Siding
  Spline & Gasket Designs for Log Buildings
  Spline Gaps & Gasket Omissions
  Types of Log Houses - Log Choices
  Vertical Log Walls on Cabins & Homes
  Wall Insulation Values in Log Homes
LOG HOME WALL INSULATION VALUES

• Thanks to Arlene Puentes for the photograph of a checked log in a log home exterior. Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY. Photographs © Arlene Puentes 2006 All Rights Reserved. Text © Daniel Friedman Arlene Puentes 2008 All Rights Reserved.
• "The Logless Log Home," Jim Robbins, New York Times, 02/25/2010 Home section, p. D1 & D6.
• "Shop Talk," Martin Mintz, AIA, Builder Magazine, April 1986, detailed solutions for log shrinkage movement by using a "T" jamb at windows and doors. A January 1986 Builder Magazine article shows window installation details in 8" thick log walls.
• "Caulking, Chinking, Insulators, Sealants - which System works Best," Log Home and Alternative Housing Builder, Nov-Dec 1983.
• Lincoln Log Homes Marketing, Inc., 6000 Lumber Lane, Kannapolis NC 28081 704-932-6151
• Insulating Characteristics of log homes were neatly summarized by Roger Rawlings in "Log Homes in a New Light," Rodale's New Shelter, April 1983, p. 28
• Merrimac Log Homes, Henniker, NH, sells log home products, milled log home kits, log siding, and log home plans and log home construction accessories. 866-637-7462 or logs@mlhnh.com - merrimacloghomes.com
• PermaChink Systems, Knoxville TN 800-548-1231 provides a range of log chinking products, coatings, and sealants for log and other wood buildings.

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