Why Log Home Settling Matters
When log walls are built, the wood is almost always at a higher moisture content than it will reach once the home is heated and occupied. As the logs dry, they shrink primarily in the radial direction (across the diameter). Because logs are stacked, this shrinkage compounds across every course — a 12-inch-diameter log wall with 7 courses and 4% radial shrinkage loses roughly 3–4 inches of height over time.
If settling is not planned for, the results are expensive and sometimes dangerous: doors that bind or shatter, windows that crack, plumbing stacks that fail, and stairways that rack. The solution is to build in settling spaces above every rigid component — doors, windows, interior partition walls, and support posts — and install adjustable screw jacks beneath any posts that carry dead loads.
The Three Components of Log Wall Settling
- Radial shrinkage — the dominant component. Logs lose diameter as moisture content drops below the fiber saturation point (~30%). Species-specific radial shrinkage values from the USDA Wood Handbook are used here.
- Compaction — in cope/scribe-fit walls, the sharp ridge of the cope presses into the log below under the weight of the structure. This can account for up to 1% of diameter per course in full-cope construction, much less in flat-to-flat contact styles.
- Safety allowance — an additional buffer (typically 1%) for seasonal MC swings, local humidity variation, and construction uncertainty.
Fiber Saturation Point & Partial Shrinkage
Wood does not begin to shrink until moisture content drops below approximately 30% (the fiber saturation point, FSP). Above FSP, the cell walls are saturated and no dimensional change occurs. Once below FSP, shrinkage is approximately linear. The Wood Handbook relationship is roughly 1% change in dimension per 4% change in MC (radial direction), which is equivalent to saying total shrinkage (green-to-oven-dry) is spread linearly across the 30% MC range from FSP to 0%.
This calculator uses your actual starting MC and site EMC to compute the partial shrinkage actually expected — not a worst-case green-to-oven-dry number.
Formula (per log course):
Partial shrinkage fraction = (S_radial_total% / 100) × (MC_start − MC_emc) / FSP
Shrinkage per log (in or mm) = log_diameter × partial_shrinkage_fraction
Compaction per log = log_diameter × compaction_factor (0 – 0.01 depending on style)
Safety addition = log_diameter × safety% / 100
Total settling = (shrinkage + compaction + safety) × number_of_courses
FSP assumed = 30% | Source:
USDA Wood Handbook Chapter 4, FPL-GTR-282
Estimates are for planning guidance only. Actual settling varies with log straightness, bark removal, stacking method, local humidity cycles, and construction details. Consult a qualified log home builder or structural engineer before finalizing settling allowances for permitted construction.
Frequently Asked Questions
How much does a log home wall typically settle?
Total settling depends on species, log diameter, number of courses, and starting moisture content. A typical 8-ft (2.4 m) scribe-fit wall built from green softwood logs can settle 1–4 inches (25–100 mm), with most occurring in the first two heating seasons. Use this calculator with your actual inputs for a site-specific estimate rather than relying on rule-of-thumb ranges.
How much space do I leave above a door or window in a log home?
The settling gap above an opening should match the total calculated wall settling over the full wall height — not just the height above the opening. Settling occurs across the entire stacked wall, and rigid frames will be crushed by the descending logs unless the full settling space is provided. This calculator outputs that exact value. Common values range from ¾ in (19 mm) for pre-dried laminated logs to 4 in (100 mm) for green full-scribe walls.
What is screw jack travel in a log home and how often should I adjust it?
Screw jacks support posts that carry floors, beams, or roofs independently of the settling log wall. As the log wall shortens, jacks must be lowered to keep the supported structure level. Jack travel equals the full predicted wall settling. Most builders adjust jacks every 6–12 months during the first two heating seasons, and again the third year if needed. After that, the logs are usually near equilibrium and no further adjustment is required.
Does drying logs before construction eliminate settling?
Not completely, but it reduces it significantly. Pre-drying logs from green (~28–35% MC) to air-dried (~18–22%) removes much of the moisture before construction, cutting settling by roughly 30–50% depending on species and site EMC. Kiln-dried logs (12–16% MC) reduce it further. The calculator accounts for this: enter your actual starting MC and observe how settling drops as you lower that value.
Which species settles the least?
Western Red Cedar (2.4% radial) and Eastern White Pine (2.1%) have the lowest radial shrinkage of commonly used log-home species, making them the most stable choices. Douglas Fir Coast type (4.8%) and Western Larch/Tamarack (5.1%) settle considerably more. All other factors equal, Cedar and Pine walls will move roughly half as much as Larch walls of the same diameter and course count.
What is equilibrium moisture content (EMC) and how do I find mine?
EMC is the moisture content that wood reaches when it stabilises with the surrounding air. It varies by region and season. In dry continental interiors (e.g., Montana, Alberta interior), EMC is typically 6–9%. On humid coasts (Pacific Northwest, Atlantic), it ranges 12–16%. The USDA Forest Products Laboratory publishes EMC tables by location and season. A conservative approach: use the average annual EMC for your site, not the lowest seasonal value.
What settling space does an interior partition wall need?
Interior frame partition walls attached to exterior log walls must have a gap at the top (or a "floating" connection) equal to the full settling amount. If there is no gap, the descending log wall will transfer load into the partition, causing it to bow, crack, or fail. This calculator outputs the recommended partition gap — the same value as the door/window settling space.