United States 

Department of 

Agriculture

Forest Service

Pacific Northwest 

Research Station

General Technical Report

PNW-GTR-782

March 2009

House Log Drying Rates 

in Southeast Alaska for 

Covered and Uncovered 

Softwood Logs

David Nicholls and Allen Brackley
The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of 

multiple use management of the Nation’s forest resources for sustained yields of wood, 

water, forage, wildlife, and recreation. Through forestry research, cooperation with the 

States and private forest owners, and management of the National Forests and National 

Grasslands, it strives—as directed by Congress—to provide increasingly greater service 

to a growing Nation.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and 

activities on the basis of race, color, national origin, age, disability, and where applicable, 

sex, marital status, familial status, parental status, religion, sexual orientation, genetic 

information, political beliefs, reprisal, or because all or part of an individual’s income 

is derived from any public assistance program. (Not all prohibited bases apply to all 

programs.) Persons with disabilities who require alternative means for communication of 

program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET 

Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write 

USDA, Director, Office of Civil Rights, 1400 Independence Avenue, SW, Washington, DC 

20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal 

opportunity provider and employer.

Authors 

David Nicholls is a forest products technologist and Allen Brackley is a research 

forester, Alaska Wood Utilization Research and Development Center, 204 Siginaka 

Way, Sitka, AK 99835.
Abstract

Nicholls, David; Brackley, Allen. 2008. House log drying rates in southeast 

Alaska for covered and uncovered softwood logs. Gen. Tech. Rep. PNW-GTR782. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 18 p. 

Log moisture content has an important impact on many aspects of log home construction, including log processing, transportation costs, and dimensional stability 

in use. Air-drying times for house logs from freshly harvested trees can depend on 

numerous factors including initial moisture content, log diameter, bark condition, 

and environmental conditions during drying. In this study, we evaluated air-drying 

properties of young-growth Sitka spruce (Picea sitchensis (Bong.) Carr) and of 

western hemlock (Tsuga heterophylla (Raf.) Sarg.) from logs harvested in southeast 

Alaska. For each species, we considered inside storage in a warehouse vs. outside 

storage, as well as debarked logs vs. logs with bark remaining, resulting in four 

experimental treatments. We considered moisture losses after 8 and 12 months of 

air drying. There was considerable moisture loss for Sitka spruce logs, and much of 

the drying occurred during the first 8 months. Fastest drying rates for both species 

were for peeled logs with inside storage. Western hemlock logs showed higher 

moisture content and greater moisture content variation (vs. Sitka spruce), and in 

most cases would require additional drying beyond the 12-month study period to 

produce satisfactory house logs. Results of this study are significant because they 

can help entrepreneurs determine appropriate levels of capital investment (e.g., 

land, covered storage, debarking equipment), as well as whether to dry and process 

logs in southeast Alaska vs. some other location. This study found that a leading 

option for local producers would be to peel Sitka spruce logs, then air dry indoors 

for between 8 and 12 months. Another effective strategy would be to peel western 

hemlock logs, then air dry indoors for 12 months.

Keywords: Sitka spruce, western hemlock, moisture content, air drying.
House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

1

Introduction

Large acreages of second-growth timber in southeast Alaska, originally harvested 

during the pulp mill era (approximately from the 1950s through the 1990s), are 

now reaching commercial size. Thinned stands can result in greater forest productivity and enhanced wildlife benefits and provide economic value from wood 

products, including sawn lumber, round wood, and biomass. Thinning can be an 

important means of influencing stand development while increasing the volume, 

size, and quality of wood produced from forests. Thinning can also help develop 

stand structures and characteristics for other values, such as wildlife or aesthetics 

(Duncan 2002). Within mixed stands of western hemlock (Tsuga heterophylla 

(Raf.) Sarg.) and Sitka spruce (Picea sitchensis (Bong.) Carr), as found in southeast Alaska, the ratio of western hemlock to other species can be an important 

factor determining tree response to thinnings (Graham et al. 1985). 

In many cases, thinnings can yield some merchantable material, but not 

generate product revenues sufficient to cover harvesting costs (Fight et al. 2004). 

Precommercial thinnings can be conducted to redistribute growth to remaining 

stems and assist crown development of crop trees early in rotations. This can 

allow mixed stands of western hemlock and Sitka spruce to reach commercial size 

in as little as 25 to 30 years (Greene and Emmingham 1986). In southeast Alaska, 

important timber management goals are to enhance wildlife habitat in secondgrowth softwood stands while also improving stand quality. During fiscal years 

2004 through 2007, an average of 5,449 acres per year were precommercially 

thinned in the Tongass National Forest.1

Timber production in southeast Alaska will likely encompass a range of 

products types, including round logs and rough sawn green lumber for both 

domestic and export markets (Brackley et al. 2006). Log home construction is one 

potentially important use of round logs from thinned second-growth stands. An 

important distinction between round logs for export markets vs. round logs for log 

home construction is the potential for some degree of value-added processing with 

the latter. This could include log drying, bark removal, pre-assembly operations 

(such as cutting notches), log turning, or complete assembly of log home kits, all 

or part of which could take place within Alaska.

Log moisture content (MC) has an important impact on transportation costs 

and the in-service performance and durability of log homes (including dimensional stability). Therefore, it is worth exploring the feasibility of drying logs 

1 Spores, S. 2008. Personal communication. Forest silviculturist, Tongass National Forest, 

648 Mission Street, Ketchikan, AK 99901.

Log moisture content 

has an important impact 

on transportation costs 

and the in-service 

performance and 

durability of log homes.
2

GENERAL TECHNICAL REPORT PNW-GTR-782 

shortly after harvest. Air-drying times for house logs from freshly harvested trees 

can depend on numerous factors:

• Initial and final MC

• Species

• Wood specific gravity

• Log diameter

• Presence of defects (including knots) in logs

• Drying season (summer vs. winter)

• Other weather-related variables (including local wind direction, windspeed, 

and log orientation with respect to prevailing wind and rain)

• Debarked logs vs. bark remaining

• Stacking arrangement of logs

• Covered or uncovered logs.

Timbers can be dried by a number of different methods including conventional 

dry kilns, predryers, fan sheds, or air drying. Often, a tradeoff exists between 

capital investment and drying time. For example, a capital-intensive dry kiln could 

be used to dry logs quickly, whereas an air-drying yard (requiring little or no 

capital investment) would dry logs less quickly. When drying house logs and cants 

in conventional dry kilns (Gorman and Steinhagen 1992) and in radio frequency/

vacuum kilns (Kang et al. 2004), a concern is the development of visible checks 

and v-cracks that could diminish the appearance of the finished product. Thus, an 

objective of the current study is to determine whether satisfactory air-drying rates 

can be obtained in southeast Alaska without the need for any dry kiln equipment 

purchases, while still maintaining satisfactory log appearances.

In this study, we evaluate outdoor air-drying conditions and rate of moisture 

loss of Sitka spruce and western hemlock logs in open air conditions vs. covered 

conditions, over a period of about 12 months in Ketchikan, Alaska. Knowledge 

gained could allow economic use of softwood logs from second-growth stands 

within the Tongass National Forest. Accurate information regarding log drying 

rates could assist wood products managers in deciding whether to:

• Invest in dry kilns, predryers, and/or heated buildings

• Dry logs in the debarked condition (vs. bark remaining)

• Ship logs to export destinations in the green condition vs. 

air-dried condition

• Consider additional value-added processing of logs within Alaska 

(such as log home kits).
House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

3

Background and Literature Review

Wood exchanges moisture with the surrounding air. If stored in a specific location, the moisture content of the wood material will come into equilibrium with 

the climatic conditions to which it is exposed. This condition is called equilibrium 

moisture content (EMC) and it can either be determined by referencing published 

tables in wood science texts and research papers, or by calculations based on the 

relative humidity and temperature of the location (Simpson 1998, USDA FS 1999). 

For example, an EMC of 12 percent (ovendry basis) is obtained by constant exposure to climatic conditions of 65 °F and a relative humidity of 65 percent. At 65 °F, 

a relative humidity above 65 percent will result in an EMC greater than 12 percent, 

and at relative humidity levels below 65 percent, the EMC will be lower. Likewise, 

if relative humidity is constant at 65 percent, temperatures above 65 °F will result 

in equilibrium at lower moisture contents, whereas temperatures below 65 °F will 

result in higher EMCs.

The potential for drying wood in outdoor locations in southeast Alaska is 

limited by a climate that is characterized by high rainfall and humidity, when compared to other regions of the country. The EMC of wood in Juneau, Alaska (about 

150 miles north of Ketchikan, Alaska), varies seasonally from about 13.5 percent 

to more than 18 percent. During this study, the calculated monthly average EMC at 

Ketchikan Airport was even higher, ranging from 17.2 to 22.5 percent (table 1).

Table 1—Equilibrium moisture content of 

wood, exposed to outdoor atmosphere, 

Juneau and Ketchikan, Alaska

Equilibrium moisture content

Month Juneau Ketchikan

January 16.5 22.5

February 16.0 21.0

March 15.1 20.8

April 13.9 19.7

May 13.6 17.2

June 13.9 17.6

July 15.1 18.3

August 16.5 19.8

September 18.1 22.1

October 18.0 21.9

November 17.7 18.3

December 18.1 22.0

Source of Juneau data: Simpson 1998 (year of data 

collection not reported).

Source of Ketchikan data: Weather-warehouse 

2007 (calculated by using 2006 and 2007 weather 

data in the procedures published in Simpson 1998).
4

GENERAL TECHNICAL REPORT PNW-GTR-782 

Wood “chunks” have been found to dry relatively quickly during as little as 60 

days of outdoor exposure in northern Michigan (Sturos 1984). Aspen (Populus spp.) 

chunks dried from more than 50 percent MC (green basis) to less than 20 percent 

MC (green basis). Moisture loss for sugar maple (Acer saccharum Marsh.) chunk 

drying was not as pronounced. 

Small-diameter logs from ponderosa pine (Pinus ponderosa Dougl. ex Laws) 

and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), air-dried in Hayfork, 

California, also showed the greatest moisture loss during the first 60 days of drying 

(Simpson and Wang 2004). When small-diameter ponderosa pine logs were air 

dried during summer months, MC decreased from about 130 percent to about 20 

percent (ovendry basis) in only 20 days. During winter air-drying, approximately 

the same moisture loss was realized in about 4.5 months (Simpson and Wang 2004). 

Similar trends were noted for Douglas-fir logs (i.e., air-drying periods were considerably longer during winter months, when drying started in October). The Hayfork 

study used multiple linear regression to fit experimental data to drying curves. 

Faster drying conditions would be expected in the Hayfork study (vs. Ketchikan) 

owing to the relatively dryer climate and use of smaller diameter, debarked logs.

Similar air-drying studies have also been completed in New Mexico and 

Arizona (USDA FS 2000). Primary results from this series of air-drying tests on 

small-diameter logs in arid locations include:

• On average, peeled logs lost roughly 2.5 percent MC per day (at moistures 

above fiber saturation)

• Moisture content loss below fiber saturation content was much slower 

(dropping from about 35 percent to 15 percent MC over a 2-month period)

• Unpeeled logs dried at only one-tenth the rate of peeled logs (i.e., no bark 

remaining).

For short-term air-drying studies, the starting date can be an important consideration. Simpson and Hart (2000) indicated air drying times for thick lumber 

ranging from less than 2 months to greater than 9 months, depending on whether 

drying starting during summer or autumn. Here, final MC was 20 percent. In the 

current study, we avoid seasonal drying variations by considering a 12-month 

study period.

The importance of bark in influencing drying times was also demonstrated with 

aspen logs (Defo and Brunette 2006). Here, a simulated log drying model predicted 

one-third the drying time when all the bark was removed from the logs (vs. all bark 

remaining).
House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

5

Green MC (i.e., the MC of freshly cut wood) can differ considerably by species. 

Of the two primary softwoods on Prince of Wales Island in Alaska, western hemlock had higher average green MC than Sitka spruce (table 2). An evaluation of nine 

western hemlock logs from three trees harvested near Sitka, Alaska, found that 

local MC ranged from about 31 percent to about 150 percent MC (ovendry basis) 

(Nicholls and Brackley 2003). There were no significant differences in average MC 

between sample heights (i.e., height above ground) for the trees evaluated in this 

study. However, average MCs at 9 inches from the pith were almost twice that at 

the pith (Nicholls and Brackley 2003). 

Table 2—Average moisture content of green 

wood for western hemlock and Sitka spruce

Average moisture content

Species Heartwood Sapwood

Percent (ovendry basis)

Western hemlock 85 170

Sitka spruce 41 142

Source: USDA FS 1999.

Table 2 indicates the importance of sapwood content in influencing MC for 

both western hemlock and Sitka spruce. This factor can be especially important 

for smaller diameter second-growth stems having relatively high proportions of 

sapwood. 

Procedures

Log Harvesting and Transportation

Our research material for air-drying consisted of a total of 80 bucked logs, all 

16 feet in length (40 logs of Sitka spruce and 40 logs of western hemlock). This 

material was derived from a total of 40 full-length logs (20 logs of Sitka spruce 

and 20 logs of western hemlock), all having in-woods lengths of 34 feet. Logs were 

obtained from trees harvested within the Maybeso Experimental Forest, Tongass 

National Forest, Alaska. The harvest site was within about 2 miles of the community of Hollis, Alaska, on Prince of Wales Island (about 20 miles east of Craig, 

Alaska). The harvest site was on flat terrain, at an elevation of about 200 to 300 feet 

above sea level. Stand age was about 50 to 60 years old, and the forest type was 

even-aged Sitka spruce and western hemlock.2

2 Lawton, G. 2008. Personal communication. Supervisory forester, Tongass National 

Forest, Craig Ranger District, P.O. Box 500, Craig, AK 99921.

Western hemlock had 

higher average green 

moisture content than 

Sitka spruce.
6

GENERAL TECHNICAL REPORT PNW-GTR-782 

Logs were cut to an 8-inch small-end diameter, and large-end diameter varied 

depending on natural stem taper. Large-end, inside bark log diameters ranged from 

10.1 inches to 18.3 inches, with the largest concentration between 12 and 13 inches 

(fig. 1). Log ends were coated with a commercial wax and water emulsion end 

sealer immediately after harvest to minimize moisture losses during transit. Logs 

were then barged to Ketchikan, Alaska, where they were transported by truck to 

the air-drying yard. The initial MCs and log weights were taken about 3 weeks after 

harvest. This amount of time was needed for ground transportation on Prince of 

Wales Island, followed by barging to Ketchikan.

0

2

4

6

8

10

12

14

10.0–10.9 11.0–11.9 12.0–12.9 13.0–13.9 14.0–14.9 15.0–15.9 16.0–16.9 17.0–17.9 18.0–18.9

Large end, inside bark diameter (inches)

Number of logs

Western hemlock

Sitka spruce

Figure 1—Distribution of log diameters for western hemlock and Sitka spruce house logs.

Log Preparation

Log weighing and air drying took place at the Ketchikan Wood Technology Center, 

located at Ward Cove, Alaska (near Ketchikan). A total of 20 logs for each species 

and drying condition were evaluated. Half of these logs were debarked and half 

were left with bark remaining.

The air drying conditions we evaluated were:

• Covered storage (bark remaining)

• Covered storage (debarked)

• Uncovered storage (bark remaining)

• Uncovered storage (debarked).
House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

7

The covered logs were stored indoors within a large storeroom, and therefore 

there was no exposure to direct rainfall, mist (or any liquid precipitation), or direct 

sunlight during the storage period. Individual logs were weighed using a forklift 

and a crane scale. 

The initial weighing occurred in early July 2006, the second weighing in early 

March 2007 (9 months after the initial weighing), and the third and final weighing 

occurred in late June 2007 (about 12 months after the initial weighing). Weights 

were recorded using a digital crane scale (a shackle-type dynamometer having a 

3-ton capacity), mounted between a cable assembly and a fork lift. This assembly 

was then used to suspend each log above ground. Weather records were obtained 

for conditions at Ketchikan International Airport, less than 5 miles away from the 

study site. These records were used to estimate EMC conditions at the air-drying 

site (table 1). No other measurements of temperature or relative humidity were 

taken during the drying period; therefore, the Ketchikan International Airport 

records were used for discussions related to both indoor and outdoor exposures.

Log Storage Conditions

Outdoor log storage areas were well-drained, level, and free of vegetation. Logs 

were stored above ground level, similar to what is shown in figure 2. Logs were 

numbered and labeled, indicating species, tree number, and log number. Indoor 

logs were stored on two bunks, each housing two to three rows of logs, which were 

strapped in place (fig. 3). Indoor storage was in a dry, enclosed warehouse where 

temperatures ranged from about 50 to 60 degrees Fahrenheit throughout the year. 

Past research has indicated that wood products in long-term storage in this same 

warehouse equilibrated at between 10 and 17 percent EMC (Bannister et al. 2007). 

Figure 2—Debarked logs, outdoor storage. Identification tags are attached to the log ends.

David Nicholls
8

GENERAL TECHNICAL REPORT PNW-GTR-782 

Therefore, in our study we estimate the EMC for indoor log storage to be at least 

12 percent. No attempt was made to alter or monitor the temperature or relative 

humidity within the warehouse during the 12-month storage period.

Initial Log Weighings and Moisture Determinations

Initial MCs were determined by removing “cookies” (i.e., cross sections approximately 1 inch thick) from close to each log end and from the center. Next, cookies 

were manually debarked, and then oven-dried (see the appendix for more information). Next, half of the 16-foot logs (40 in number) were debarked before initial log 

weighing. Logs were debarked manually using small scribes and chisels. After 

debarking, logs were once again weighed (to determine weight without bark). Bark 

content is an important property that shows variation between species, and therefore we wanted to quantify this aspect of the study. 

Figure 3—Logs in indoor storage. Identification tags are attached to the log ends.

David Nicholls
House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

9

Once we determined cookie moisture content, the estimated dry weight for 

each log was calculated (see the appendix for details). At the completion of the 

study, it was noted that the actual weights of two logs were less than the estimated 

dry log weights which had been calculated. The possible reasons for this include 

(a) end drying could have occurred between harvest and initial log weighing (about 

3 weeks), even though the ends were sealed, and (b) the average cookie MC from 

the ends of each log did not provide a sufficiently accurate estimate of log MC. 

Regardless, log MC and the weight derived from the driest samples are a function 

of the EMC of the storage areas. Given this fact, we developed a process to adjust 

all log MCs (by increasing the initial, estimated green log weights) so that the 

driest logs were based on the equilibrium condition. This process is described in 

the appendix. The amount of adjustment was based on EMCs historically obtained 

within the covered storage areas in Ketchikan. The adjustments we used ensured 

that none of the final MCs, calculated using estimated dry log weight, would be 

less than those resulting from the prevailing EMC conditions in the storage area. 

If logs had dried to less than the EMC conditions, end checks and surface cracks 

should have resulted (which did not occur, suggesting that the calculations needed 

adjustments). We report log MC values based both on estimated dry log weight and 

adjusted, estimated dry log weight. 

Results

Moisture Content Variations Among Species and 

Storage Conditions

Western hemlock logs had overall higher MC versus Sitka spruce logs (figs. 4 and 

5). Initial MCs were typically at least 10 percent higher for western hemlock. Sitka 

spruce logs dried more quickly than western hemlock during the initial 8 months, 

especially for inside storage conditions. For outside storage, unpeeled logs dried 

very slowly, with final (12 month) MCs ranging between about 80 and 100 percent 

(ovendry basis) for both species. Average MC for western hemlock logs (unpeeled, 

outside) even increased during the first 8 months of storage. For outside storage 

of peeled logs, each species exhibited good drying characteristics, finishing the 

12-month period with average MCs of close to 40 percent, and relatively little 

difference between 8-month MCs (figs. 4 and 5, table 3). One limitation of this 

study is that after the final weighing, logs were not inspected for end checking, 

discoloration, or other weathering.

Western hemlock logs 

had overall higher 

moisture content 

versus Sitka spruce 

logs.
10

GENERAL TECHNICAL REPORT PNW-GTR-782 

Figure 5—Average adjusted moisture content for Sitka spruce logs air dried in Ketchikan, Alaska, under four 

storage conditions.

Figure 4—Average adjusted moisture content for western hemlock logs air dried in Ketchikan, Alaska, under 

four storage conditions.

0

20

40

60

80

100

120

140

Peeled, Unpeeled, Peeled, Unpeeled,

inside inside outside outside

Storage conditions

A

djusted

m

oisture content

(percent, o

vendry

weight)

0 months

8 months

12 months

0

20

40

60

80

100

120

Adjusted moisture content (percent, ovendry weight)

Peeled, Unpeeled, Peeled, Unpeeled,

inside inside outside outside

Storage conditions

0 months

8 months

12 months
House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

11

Table 3—Average moisture content of western hemlock and Sitka spruce house logs during approximately 

12 months of air drying in Ketchikan, Alaska

Mean moisture content

Bark Storage Number Green log

Species condition location of logs weighta 0 months 8 months 12 months

Percent (ovendry basis)

Western hemlock Unpeeled Inside 10 Estimated 98.2 67.8 57.3

Adjusted 114.1 81.4 70.2

Sitka spruce Unpeeled Inside 10 Estimated 89.5 35.0 23.0

Adjusted 105.8 46.8 33.6

Western hemlock Unpeeled Outside 10 Estimated 100.6 104.1 87.9

Adjusted 114.6 118.2 100.7

Sitka spruce Unpeeled Outside 10 Estimated 86.3 84.3 63.8

Adjusted 101.3 99.7 77.0

Western hemlock Peeled Inside 10 Estimated 102.2 43.9 25.2

Adjusted 116.5 54.0 34.1

Sitka spruce Peeled Inside 10 Estimated 87.6 26.5 13.1

Adjusted 101.2 35.8 21.4

Western hemlock Peeled Outside 10 Estimated 101.3 55.7 34.3

Adjusted 114.8 66.3 43.3

Sitka spruce Peeled Outside 10 Estimated 89.7 49.2 28.7

Adjusted 104.8 61.1 39.0

a This table includes moisture contents based on the initial estimates of green log weights and also adjustments that were made to 

the estimated weights once it was determined that the final moisture contents were not accurate (less than the equilibrium moisture 

content of the storage location). The adjustment to the green log weights was an increase by 17 percent.

The overall greatest moisture losses (i.e., fastest drying) occurred in peeled 

logs, stored inside. The overall least moisture losses (i.e., slowest drying) occurred 

in unpeeled logs, stored outside. Log home producers would be most interested in 

identifying the point at which drying could be stopped and still produce a goodquality house log (i.e., one with minimal shrinking). All of the final MCs were 

greater than the recommended acceptable MC of 15 percent for house logs (Gorman and Steinhagen 1992). Another important consideration would be for logs to 

be oriented so that the largest cracks are facing down, and therefore do not collect 

water. Sometimes house logs are “kerfed” before drying to facilitate development 

of primary checks at a specific location.

For Sitka spruce logs, the effect of peeling (vs. leaving bark on) was to reduce 

MC by about 10 to 15 percent for inside storage (fig. 5). For outside storage (Sitka 

spruce) the effect of peeling on MC was more pronounced, with peeled logs generally about 40 percent MC dryer than unpeeled logs (for both 8 and 12 months of 

storage). For western hemlock logs, the effect of peeling (vs. leaving bark on) was 

somewhat more pronounced (fig. 4), especially for outside storage. 

It should be noted that all 40 of the logs for this study were debarked manually 

in about 3 hours (by a crew of six workers), suggesting that it could be a relatively 

quick process under certain production scenarios. Automated debarking equipment 

The overall greatest 

moisture losses 

occurred in peeled 

logs, stored inside.
12

GENERAL TECHNICAL REPORT PNW-GTR-782 

could also be considered when higher production volumes are needed. All of the 

trees used in this study were harvested in late spring, resulting in potentially easier 

bark removal than if harvests had occurred during other seasons.

Another factor that potentially influences MC determinations is wet pockets, 

zones of unusually high moisture sometimes found in western hemlock (Nicholls 

and Brackley 2003). If any of the MC “cookies” that were used to estimate initial 

log MC had been selected from a wet pocket, artificially high MC could result. 

Because the location of MC cookies within the original logs was fixed, we had no 

way to control for wet pockets. Nor did we attempt to determine if a given “cookie” 

was entirely or partially within a wet pocket zone.

Discussion and Conclusions

Second-growth timber from southeast Alaska could be used for house logs under a 

number of different scenarios: 

• Ship logs “as is” shortly after harvesting to a log home production facility 

in the continental United States (here logs could be either air-dried or kilndried).

• Air dry logs in Alaska, then ship to a production facility in the continental 

United States.

• Air dry logs in Alaska, followed by production of log homes or log home 

kits (also in Alaska).

• Dry logs under accelerated conditions, such as predryers or conventional 

dry kilns, before further processing (either in Alaska or a continental 

United States location).

Most log home producers do not kiln-dry their logs nor do they attempt to 

reduce moisture to construction-grade levels (typically 19 percent MC or less), 

although some producers use exclusively kiln-dried material. Other producers practice air-drying, or they utilize low-moisture content material salvaged from fires 

(Lazarus Log Homes 2008). Still other producers use material from insect attacks 

(Satterwhite Log Homes 2008). 

In other cases, log homes are built with green logs, and shrinkage and settling 

is accounted for by engineering and design. For example, in full-scribe methods, 

long logs can be debarked by hand and then built up row by row to create the final 

shell (Husky Logwork 2008). Other techniques might require more careful control 

of MC; for example, log home kits in which processed logs are in close contact with 

windows, exterior doors, and other components that have likely been kiln-dried. 

Many other variations of log home production are possible including turned logs 

(Rocky Mountain Log Homes 2008) and glulam members (Glu-lam-log 2008).
House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

13

Our current study of air-drying house logs in Ketchikan, Alaska, has shown 

that a leading option for local producers would be to peel Sitka spruce logs, then 

air-dry indoors for between 8 and 12 months. Doing so should allow sufficient 

reductions in shipping weight and would minimize shrinkage as logs dry to their 

final MC in-service. Another very good option would be to peel western hemlock 

logs, then air-dry indoors for 12 months. If outdoor storage is the only option for 

air-drying, our study strongly suggests using only peeled logs. Unpeeled logs 

should not be air-dried outside in environments similar to Ketchikan, given the very 

low drying potential during the first 8 months (and relatively little drying during 12 

months). 

These results might be different for outside storage if rainfall were considerably different from that experienced in this study. However, Ketchikan is one of the 

highest rainfall locations in southeast Alaska, and EMC conditions for logs often 

exceed 20 percent (see table 1). Further, the logs dried in this study were “short” 

logs, approximately 16 feet long. Log home producers using longer logs (or fulllength logs) could experience considerably different results under similar air-drying 

conditions. A limitation of this study was that the log-drying period started and 

ended during summer months. It is not known how this would compare to a similar 

(12 month) air-drying study that was started and ended during other seasons.

The above discussion illustrates that there are many important variables influencing log-drying rates in uncontrolled, outdoor conditions. Therefore, these drying 

results must be considered on a case-by-case basis, according to the log resources 

and production processes of individual manufacturers.

Significance for Log Home Production

Whether logs are used for custom home construction, for log home kits, or for other 

uses could influence strategies for air drying as well as required final MCs. For log 

home producers considering air drying house logs from southeast Alaska, several 

capital investment decisions could be relevant. Some of these investment decisions 

could include:

• Whether to debark logs (by using either manual labor for scribing, or by 

using a mechanical debarker)

• Whether to dedicate land for use as an air-drying yard (vs. potentially 

higher value uses)

• Whether to dedicate building or warehouse space for air drying (vs. potentially higher value uses)

• Whether to air-dry for 8 months, 12 months, or some other period 

Peeling logs, then 

air-drying indoors 

for between 8 and 12 

months, should allow 

sufficient reductions 

in shipping weight
14

GENERAL TECHNICAL REPORT PNW-GTR-782 

• Whether to invest in predrying shed, dry kiln, or other structure having 

controlled heat and air flow for accelerated drying

• Whether to invest in an open, covered storage structure (i.e., a “T” shed), 

that could protect the peeled logs from periodic rewetting, while allowing 

air flow to aid in drying (note that this option would be less expensive than 

building enclosed, controlled-environment structures).

Acknowledgments

This research was conducted under the terms of Joint Venture PNW-06-JV11261975-287, between the USDA Forest Service, Pacific Northwest Research 

Station, Alaska Wood Utilization and Research Development Center in Sitka, 

Alaska, and the Ketchikan Wood Technology Center in Ketchikan, Alaska. We 

recognize the contributions of Dr. Kevin Curtis and Michael Hannan of the 

Ketchikan Wood Technology Center.

Metric Equivalents

When you know: Multiply by: To find:

Inches 2.54 Centimeters

Feet .3048 Meters

Miles 1.609 Kilometers

Acres .405 Hectares

Pounds 454 Grams

Degrees Fahrenheit .56(°F - 32) Degrees Celsius

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House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

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House Log Drying Rates in Southeast Alaska for Covered and Uncovered Softwood Logs

17

Appendix 

Sitka Spruce and Western Hemlock House Log Air-Drying Study 

Moisture Content Adjustment Procedures

1. The basic formula used to calculate moisture content (USDA FS 1999) is:

MC = [((WG – WOD)/WOD)] × 100

where:

MC = moisture content (percent),

WG = initial green weight, and

WOD = ovendry weight (stabilized condition when dried at 100 °C ± 5 °C).

Because the entire log cannot be used to measure ovendry weight (that would 

prevent leaving any drying material to be measured), samples are cut from the 

log and used to determine MC. The cutting of samples for MC determination is a 

destructive process and the samples must be collected so that the integrity of the 

log is maintained during the period of drying. 

2. In this study, MC was calculated by cutting samples (“cookies”) from the ends 

and midpoints of the 35-foot house logs. The initial green weight (WG) and ovendry weight (WOD) of the cookies were measured and used in the formula above to 

calculate MC. Log MC was considered as the average of the butt and top disk from 

each 16-foot section. Given the average green MC from the cookies, the projected 

dry log weight was calculated by using algebra to solve for WOD in the formula 

presented in step 1. In this example that follows, log 1B was a 16-foot Sitka spruce 

with an initial green weight of 442 pounds. The initial MC from the cookies was 

95.9 percent. Given these values, the estimated dry weight of the log was calculated 

using the following formula:

WOD = WG/[(1.0 + (MC/100))]

The estimated ovendry weight of the above log would be calculated as:

WOD = 442 lbs/[1.0 + (95.9/100)]

WOD = 442 lbs/1.959

WOD = 226 pounds

3. When the final log weight measurements were obtained, it was determined that 

some of the dry weights (two logs exposed to the most severe drying conditions) 

were lower than the initially estimated dry weights, as calculated in step 2 above. 

This result may have been due to drying of the logs (and sampled portions) prior 

to initial measurements. It is noted that the logs were harvested in late May and 
18

GENERAL TECHNICAL REPORT PNW-GTR-782

delivered to Ketchikan in June, and this period was during some of the best drying days during the summer of 2006. Another possibility is the use of samples, 

although precise, may not provide accurate estimates of log MC. Regardless, the 

final weights lower than the predicted dry log weights indicated that the original 

green weights needed to be adjusted upward.

4. A check of the conditions of log storage indicate that for the drying period the 

logs that were stored under cover were in a building that historically had a yearround temperature of 65 °F and a relative humidity of 60 percent. These conditions 

are similar to a system that would have a wood equilibrium moisture content of 

12 percent. Given these facts, it was assumed that the best approach to adjusting 

MC was to increase green log weights, until the final equilibrium minimum MC of 

peeled Sitka spruce logs was equal to 12 percent. 

5. The minimum final MC of the logs stored in the inside location were therefore 

adjusted to be no lower than 12 percent. All logs inside and outside were adjusted to 

reflect a uniform rate of drying in all logs, prior to the weighing in Ketchikan. The 

factor required to create the above relationship was a 17-percent increase in initial 

green weights. The green MC (MC of freshly cut wood) calculated by using either 

the estimated green log weight or the adjusted green log weight, both create average 

values that are well within the reported range of green MC for these two species. 

The relative change in log weights is the same regardless of the estimated basis of 

green material that is used to calculate change in moisture content over the period 

of the study.
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