United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

Research

Paper

FPL-RP-489

Moisture Content

and the Shrinkage

of Lumber

David W. Green
Abstract Research Highlights

The basis for the shrinkage factors given in the

American Softwood Lumber Standard, PS 20-70, is

reviewed. Using the PS 20-70 recommendations and

previous work on the shrinkage of Douglas-fir and

redwood 2-in dimension lumber, equations are derived

for calculating the shrinkage of lumber as a function of

moisture content.

Keywords: Shrinkage, moisture content, lumber,

Douglas-fir, redwood.

January 1989

Green, David W. 1989. Moisture content and the shrinkage of

lumber. Res. Pap. FPL-RP-489. Madison, WI: U.S. Department of

Agriculture, Forest Service, Forest Products Laboratory. 11 p.

A limited number of free copies of this publication are available to

the public from the Forest Products Laboratory, One Gifford Pinchot

Drive, Madison, WI 53705-2398. Laboratory publications are sent to

over 1,000 libraries in the United States and elsewhere.

The American Softwood Lumber Standard, PS 20-70,

lists specific shrinkage factors from green to 15-percent

moisture content that were used historically to set green

lumber dimensions for most species (2.35 percent for

thickness and 2.80 percent for width). The standard

does not provide a means of adjusting lumber

dimensions to any other moisture content. The standard

also does not provide specific shrinkage factors for

species such as redwood and the cedars, which shrink

less than most species. Rule-writing grading agencies

need equations for adjusting lumber dimensions to any

moisture content when assigning allowable properties

from in-grade type data (Green 1983, Green and

Evans 1987).

Using the PS 20-70 recommendations and an assumed

green moisture content of 28 percent, we derive

equations that can be used with most species to

calculate the shrinkage of lumber as a function of

percent moisture content M. These equations are

Sw = 6.031 - 0.215M

St

 = 5.062 - 0.181M

where S is the percent shrinkage from green to some

percent moisture content M and subscripts t and w

denote thickness and width of the lumber. These

equations are assumed valid between 8- and 19-percent

moisture content. Results predicted using these

equations compare favorably with data collected in

recent studies.

Using the PS 20-70 recommendations, an assumed

green moisture content of 22 percent, and the

historical studies used to establish those recommendations, similar equations are derived for redwood. These

equations

Sw = 3.457 - 0.157M

St = 2.816 - 0.128M

are also assumed valid between 8- and 19-percent

moisture content.

As additional data become available, we recommend

that the applicability of these equations be evaluated

for a variety of species.

The Forest Products Laboratory is maintained in cooperation with

the University of Wisconsin.
Moisture Content

and the Shrinkage

of Lumber

David W. Green, Engineer

Forest Products Laboratory, Madison, WI

Introduction

Safe structural design with wood is based on the

load-carrying capacity of structural members. To

calculate this capacity, a designer looks up an allowable

member strength (such as the allowable modulus of

rupture, Rbook) and multiplies this by a section

property calculated using assumed dimension at some

reference moisture content (such as the section modulus

in bending, Sbook).1 However, in the in-grade testing

program (Green 1983, Green and Evans 1987) we are

testing real lumber and measuring its actual dimensions

at time of test. For the design process to work

correctly, the product of assumed strength and assumed

section property must equal the product of the

measured values. For bending,

R · S = Rbook · Sbook (1)

where R and S are measured experimentally and Rbook

and Sbook are tabulated values given in engineering

design codes.

All terms in equation (1) are usually calculated at three

standard levels of moisture content: 12 percent,

15 percent, and green. Procedures are available for

adjusting mechanical properties for changes in moisture

content (Green and Evans 1988). The objective of

this report is to establish procedures for similarly

adjusting section properties.

Size Provisions in

the American Softwood

Lumber Standard

Size requirements for softwood lumber of most species

produced in the United States are given in the

American Softwood Lumber Standard (NBS 1986).

Footnote 3 of that standard states that the “minimum

green sizes are based on shrinkage factors of

2.35 percent in thickness and 2.80 percent in width

from the fiber saturation point to a 19-percent

maximum moisture content. . . . ” No reference is given

in the standard for these shrinkage factors. Smith and

Wood (1964) stated that various data on shrinkage

related to moisture content were studied by the

American Lumber Standards Committee when

establishing these shrinkage factors. They note that the

factors of 2.35 and 2.80 were based on

recommendations of the Forest Products Laboratory

(FPL) made in April 1963. Further, they stated that

these factors are based on “average shrinkage values to

15-percent average moisture content. . . . ” However,

they did not provide equations for calculating shrinkage

at other moisture content levels and give no definition

for green moisture content.

No specific shrinkage recommendations are made in the

standard for redwood, western redcedar, or northern

white-cedar.2,3 However, after presenting a table of

standard green sizes applicable to most species, it is

noted that “somewhat smaller green sizes” would be

adopted for redwood and western redcedar “in

recognition of smaller shrinkage values.”

1

This argument holds for other material property and section property

products, e.g., modulus of elasticity (MOE), moment of inertia (I), crosssectional area (A).

2

For the purpose of reinspection, shrinkage that may occur after dressing to

standard size is recognized through a tolerance of 0.7-percent shrinkage per

each 4 percentage points of moisture content for redwood and the cedars.

3A batch of lumber with a maximum moisture content of 19 percent is assumed

to have an average moisture content of 15 percent, and a batch of lumber with

a maximum moisture content of 15 percent is assumed to have an average

moisture content of 12 percent (ASTM 1987).
Development of Adjustment

Formulas for Calculating

Lumber Shrinkage

FPL Reports for Lumber

The apparent basis for the FPL recommendation to the

American Lumber Standards Committee was detailed

by Comstock (1965). The study measured dimensional

change for specimens having growth ring angles of

0° (flatsawn), 15°, 30°, and 45°. The 30° results were

in good agreement with other studies using randomly

selected lumber (Comstock 1965, p. 6). For a ring angle

of 30°, shrinkage4 values were 2.80 percent in width

and 2.34 percent in thickness for coast-type Douglas-fir

dried to a 15-percent moisture content (table 1). The

equivalent values for redwood are 1.10 percent in

width and 0.89 percent in thickness. The 30° shrinkage

values for Douglas-fir are almost identical to the

FPL recommendation.

Average regression equations relating percent radial

shrinkage SR and percent tangential shrinkage ST to

percent moisture content M for coast-type Douglas-fir

were derived as (Comstock 1965)

SR = 4.321 - 0.1470M (2)

ST = 6.962 - 0.2622M (3)

For old-growth redwood, the equations are

SR = 2.274 - 0.0991M (4)

ST = 3.951 - 0.1831M (5)

Using equations (2) to (5) and the equations for relating

shrinkage to growth ring orientation (Comstock 1965),

S w = ST cos

2

 O– + SR sin2

 O– (6)

S t = ST sin2 O– + SR cos

2

 O– (7)

where Sw is the percent shrinkage in width, St the

percent shrinkage in thickness, and –O the angle between

growth rings and the flat face of the board. We can

derive equations for Sw and St at a growth ring angle of

30°. For coast-type Douglas-fir, these equations are

Sw = 6.302 - 0.2334M (8)

St = 4.981 - 0.1758M (9)

4

Shrinkage = 100 x (dimension green - dimension dry) ÷ dimension green

and for redwood,

Sw = 3.5318 - 0.1621M (10)

St = 2.6932 - 0.1201M (11)

The 1963 recommendations for most species can be

obtained from equations (8) and (9). However, these

exact formulas should not be used in the development

of section property distributions for two reasons:

1. They assume a growth ring angle of 30°. In general,

the growth ring angle is not known, and it is not

feasible to incorporate such information into design

equations. It seems more appropriate to use linear

regression equations based on the 1963

recommendations but not tied specifically to the

Comstock (1965) equations. Such equations should be

valid for moisture content levels from about 8 to

19 percent.

2. The two formulas lead to different implied green

moisture content levels Mg (i.e., 27.0 percent for width

and 28.0 percent for thickness for Douglas-fir and 21.8

and 22.4, respectively, for redwood). Again, it is not

feasible to use more than one Mg value for general

design use.

Note that the Mg values used here are defined as the

value of M that gives zero shrinkage in the linear

regression evaluations.5 Because significant nonlinearity

in the moisture content and shrinkage relationship may

occur near the true fiber saturation point, this value

may not be identical to the true fiber saturation point.

Available data suggest that the Mg value is higher than

the intersection moisture content obtained by applying

a similar assumption of linearity to mechanical

properties data (Wilson 1932).

The results obtained by Wood and Soltis (1964) using

Douglas-fir, western hemlock, and Southern Pine are

comparable to the Comstock (1965) results. Wood and

Soltis fit regression equations to their individual species

data assuming Mg = 28 percent. Using the 1963 FPL

recommendations of 2.35-percent shrinkage in thickness

and 2.80-percent shrinkage in width and assuming

Mg = 28 percent, simultaneous linear regression

5Note that Mg

 defined here is in fact a function of O– for equations derived in

this manner.

2
equations of the form S = a + bM may be solved to

obtain for coast-type Douglas-fir

Sw = 6.031 - 0.215M (12)

St = 5.062 - 0.181M (13)

Development of Adjustment

Formulas for Redwood

Because the American Softwood Lumber Standard does

not list specific shrinkage factors for width and

thickness of redwood, we had to develop factors

compatible with the 1963 FPL recommendations. Using

equations (8) to (11), developed from equations

presented by Comstock (1965), we may compare the

shrinkage from green to 15-percent moisture content

for Douglas-fir and redwood lumber (table 2).

Applying the ratios from table 2 to the shrinkage

factors recommended in 1963 for most species when

dried to 15-percent moisture content,

Sw = 2.8 x 0.393 = 1.100

St = 2.35 x 0.381 = 0.895

Equations (10) and (11) assume Mg = 22 percent.

Using this value of Mg, Sw = 1.100, and St = 0.895, a

general shrinkage equation for redwood may be derived

in a manner similar to that described for equations (12)

and (13):

Sw = 3.454 - 0.157M (14)

St = 2.816 - 0.128M (15)

In the absence of other information, these equations

would seem more appropriate than equations (12) and

(13) for calculating the shrinkage of redwood, western

redcedar, and northern whitecedar.

Additional Shrinkage Information

Forintek study–Barrett and Foschi (1981) presented

equations for adjusting cross-sectional area A, moment

of inertia I, and section modulus S for changes in

moisture content:

A = Ag[1 - 0.005544(Mg - M)] (16)

I = Ig[1 - 0.10674(M g - M)] (17)

S = Sg[1 - 0.008156(M g - M)] (18)

where the subscript g denotes green.

Barrett and Foschi felt that their data were insufficient

to experimentally establish Mg. They assumed Mg = 25

based on shrinkage and moisture content data

presented by Madsen et al. (1980), stating their

assumption was consistent with previous work for

Douglas-fir (table 3).

Stamm (1964, figs. 13-1 and 13-2) investigated

volumetric shrinkage and moisture content relationships

using 2- by 2- by 6-in specimens. For 52 softwoods, the

average green moisture content was 26 percent, while

that for 107 hardwoods was 27 percent. Reanalysis of

the softwood data used by Stamm (table 4) indicates

that a value of Mg = 28 or 29 might be more

applicable to species currently included in the

U.S. in-grade testing program (table 5). Because Barrett

and Foschi (1981) did not give regression equations for

shrinkage in width and thickness, comparison of the

results obtained in various studies must be made on

some other basis. On the basis of cross-sectional area

(fig. 1), the slope of the moisture content and

dimension relationship proposed by Barrett and Foschi

is slightly steeper than those of Wood and Soltis (1964)

and Comstock (1965). The Mg = 25 value assumed by

Barrett and Foschi is lower than those used by Soltis

and Comstock and lower than those measured by

Stamm. Reanalysis of their data using a higher Mg

value would probably bring their results more in line

with the information on which the 1963 FPL

recommendations were based.

3
Figure 1–Predicted ratio of cross-sectional area at

the indicated moisture content A to that when green,

Ag. Data from (1) Barrett and Foschi (1981),

(2) Comstock (1965), and (3) Wood and Soltis

(1964). (ML88 5456)

Douglas-fir moisture content study- The cooperative

study between FPL and Forintek6 on the influence of

moisture content on the flexural properties of

Douglas-fir dimension lumber (Aplin et al. 1985)

provides additional data with which to judge the

adequacy of the 1963 FPL recommendations. We

conducted preliminary analysis of these data using the

dimensions from the matched samples7 (table 6). Plots

of the dimensions predicted using equation (12) as

functions of the measured dimensions are shown in

figure 2. In general, the equations appear to adequately

predict the experimental results. The results indicate

that a slightly lower Mg value might bring the 2-by-8

values closer to the 1 to 1 line (fig. 2c). However, data

for other species are needed to justify such changes.

6

The use of trade or firm names in this publication is for reader information

and does not imply endorsement by the U.S. Department of Agriculture of any

product or service.

7

In this analysis, only the average values of the matched sample dimensions

were used. A more complete analysis could be obtained using the dimensions

for the same pieces at two moisture content levels.

Figure 2–Comparison of actual and predicted widths for

Douglas-fir lumber, predicted from equation

(12) using data from Aplin et al. (1985). (a) 2 by 4, (b) 2 by

6, and (c) 2 by 8. (ML88 5457)

4
Conclusions and

Recommendations

Princes Risborough studies – Covington and Fewell

(1975) measured shrinkage between green and

15-percent moisture content for 2,008 joists of

European redwood and whitewood,8

 Canadian western

hemlock, and western white spruce. Sizes ranged from

44 by 100 mm (1.7 by 3.9 in) to 44 by 300 mm (1.7 by

11.8 in). Equations of the form

d1 = d2[1 - C(M2 - M1 )] (19)

were fit to the data, where d is a geometrical property,

C a shrinkage coefficient, and the subscripts 1 and 2

denote a lower and a higher moisture content value,

respectively; Mg = 28 percent was assumed. Table 7

lists average shrinkage coefficients for all sizes.

Dry-green ratios at 15 and 28 percent predicted by

equations (12) and (13) agree very well with those

predicted by equation (19) (table 8). Differences are less

than 1 percent.

Wood and Soltis study – As previously mentioned,

Wood and Soltis (1964) obtained shrinkage data on

lumber having a random growth ring orientation. The

study used a total of 360 pieces of three species

(Douglas-fir, western hemlock, and southern pine),

three grades (Construction, Standard, and Utility), and

two sizes (2 by 6 and 2 by 10) of lumber. The average

shrinkage to 15-percent moisture content compares

favorably with the 2.8-percent shrinkage in width and

2.35-percent shrinkage in thickness obtained from

equations (12) and (13) (table 9).

From the available data, the recommendations on

moisture and shrinkage relationships made by the FPL

in 1963 appear to provide an adequate basis for

adjusting test dimensions in the in-grade testing

program to design moisture content levels. Equations

(12) and (13) with an assumed green moisture content

of 28 percent are recommended for most species.

Equations (14) and (15) with an assumed green

moisture content of 22 percent are recommended for

redwood, western redcedar, and northern whitecedar.

We believe the equations are valid for predicting

average trends in the moisture content and

dimension relationship between 8- and 19-percent

moisture content.

As the data become available, we recommend that the

applicability of these equations to species other than

Douglas-fir and redwood be evaluated. 

5

8

Names used here are in accordance with established European custom.

Redwood refers to Pinus sylvestris, also called Scots pine. Whitewood refers to

Picea alba, or white spruce.
Literature Cited

ASTM. 1987. Standard methods for establishing

structural grades and related allowable properties of

visually graded lumber. ASTM designation D 245-81,

vol. 04.09. Philadelphia, PA: American Society for

Testing and Materials.

Aplin, N.; Green, D. W.; Evans, J. W.; Barrett, J. D.

1985. Moisture content and the flexural properties of

Douglas Fir dimension lumber. Res. Pap. FPL 475.

Madison, WI: U.S. Department of Agriculture,

Forest Service, Forest Products Laboratory.

Barrett, J. D.; Foschi, R. O. 1981. Moisture-stiffness

adjustment factors for Douglas-fir dimension lumber.

Res. Rep. Vancouver, BC: Forintek Canada Corp.,

Western Laboratory.

Comstock, G. L. 1965. Shrinkage of coast-type

Douglas-fir and old-growth redwood boards. Res.

Pap. FPL 30. Madison, WI: U.S. Forest Service,

Forest Products Laboratory.

Covington, S. A.: Fewell, A. R. 1975. The effect of

change in moisture content on the geometrical

properties, modulus of elasticity and stiffness of

timber. Current Paper CP21/75. Building Research

Establishment, Princes Risborough Laboratory.

Green, D. W. 1983. In-grade testing: impetus for

change in the utilization of structural lumber. In:

Proceedings, From stump thru mill: recent advances

in spruce-fir utilization technology; 1983 August

17-19; Orono, ME. Bethesda, MD: American Society

of Foresters; 191-200.

Green, D. W.; Evans, J. W. 1987. Mechanical

properties of visually graded lumber. Vol. 1. A

Summary Report. 131 p. Available from NTIS,

5285 Port Royal Road, Springfield, VA 22161;

$14.95; PB-88-159-389.

Green, D. W.; Evans, J. W. 1988. Moisture

content-property relationships for dimension lumber.

In: Proceedings of the workshop on the in-grade

testing of structural lumber, 1988 April 25-26,

Madison, WI: Forest Products Research Society.

(In production).

Madsen, B.; Jansen, W.; Zwaagstra, J. 1980. Moisture

effect in lumber. Struct. Res. Series Rep. No. 27.

Vancouver, BC: University of British Columbia,

Department of Civil Engineering.

NBS. 1986, amended. American softwood lumber

standard. Voluntary Product Standard PS 20-70.

Washington, DC: National Bureau of Standards.

Smith, L. W.; Wood, L. W. 1964. History of yard

lumber size standards. Unnumbered Rep. Madison,

WI: U.S. Forest Service, Forest Products Laboratory.

Stamm, A. J. 1964. Wood and cellulose science. New

York: Ronald Press.

Wilson, T.R.C. 1932. Strength-moisture relations for

wood. Tech. Bull. No. 282. Madison, WI: U.S.

Forest Service, Forest Products Laboratory.

Wood, L. W.; Soltis, L. A. 1964. Stiffness and

shrinkage of green and dry joists. Res. Pap. FPL 15.

Madison, WI: U.S. Forest Service, Forest

Products Laboratory.

6
Table 1 – Shrinkage from green to 15-percent Table 3 – Estimates of the fiber saturation point and

moisture content for various ring angles intersection point for Douglas-fir defect-free specimens

(Comstock 1965) (Barrett and Foschi 1981)

Species

Shrinkage (percent) for

various ring angles

0° 15° 30° 45°

Douglas-fir

Width 3.03 2.97 2.80 2.57

Thickness 2.12 2.18 2.34 2.57

Redwood

Width 1.20 1.18 1.10 1.00

Thickness 0.79 0.82 0.89 1.00

Table 2 – Shrinkage from green to 15-percent

moisture content

Dimension

Shrinkage (percent) Ratio

Douglas-fir Redwood (Redwood/

Douglas-fir)

Property Method

Intersection Mechanical test

point (Mp) Shrinkage test

Fiber Electrical

saturation conductivity

point

Moisture

content Reference

(percent)

24 Wilson (1932)

25.8 Wilson (1932)

30.5 Wilson (1932)

Equilibrium moisture 28 Stamm (1964)

content as a function

of relative humidity 

7

Width 2.801 1.100 0.393

Thickness 2.344 0.892 0.381
Table 4 – Green moisture content estimates (Stamm 1964)

Species

External Green

volumetric Specific moisture

shrinkage1

gravity2content3

(percent) (percent)

Douglas-fir

Coast

Intermediate

Rocky Mountain

Western larch

11.8

11.2

10.6

13.2

Southern Pine

Loblolly 12.3 0.47 26.2

Longleaf 12.2

Shortleaf 12.3

Slash 12.2

Hem-Fir

Western hemlock

California red fir

Grand fir

Noble fir

Pacific silver fir

White fir

11.9

11.8

–

12.5

14.1

9.4

Spruce-Pine-Fir

Alpine fir

Balsam fir

Black spruce

Englemann spruce

Jack pine

Lodgepole pine

Red spruce

White spruce

9.0

10.8

11.3

10.4

10.4

11.5

11.8

13.7

Mixed species

Eastern hemlock

Tamarack

Sitka spruce

Red pine

Eastern white pine

Western white pine

Ponderosa pine

Sugar pine

9.7

13.6

11.5

11.5

8.2

11.8

9.6

7.9

0.45 26.2

0.41 27.3

0.40 26.5

0.48 27.5

Mean 26.9

0.54 22.6

0.46 26.7

0.56 21.8

Mean 24.3

0.38 31.3

0.37 31.9

– –

0.35 35.7

0.35 40.3

0.35 26.9

Mean 33.2

0.31 29.0

0.34 31.8

0.38 29.7

0.31 33.5

0.39 26.1

0.38 30.3

0.38 31.1

0.37 37.0

Mean 31.1

0.38 25.5

0.49 27.8

0.37 31.1

0.44 26.1

0.34 24.1

0.36 32.8

0.38 25.3

0.35 22.6

Mean 26.9

Hardwoods

Aspen, trembling

Aspen, bigtooth

Cottonwood

Red alder

Yellow-poplar

Cedars

Northern white

Alaskan

Incense

Port-Orford

Western red

Other species

Eastern redcedar

Southern redcedar

Southern white cedar

Southern cypress

Cookbark fir

Lowland white fir

Mountain hemlock

Alligator juniper

Jeffrey pine

Limber pine

Mountain pine

Pitch pine

Pond pine

Sand pine

Pinyon pine

Redwood

Virgin

2nd, open

2nd, close

Pacific yew

11.5

11.8

14.1

12.6

12.3

0.35 32.9

0.35 33.1

0.37 38.1

0.37 34.1

0.38 32.4

Mean 34.2

7.0

9.2

7.6

10.1

7.7

0.29 24.1

0.42 21.9

0.35 21.7

0.40 25.3

0.31 24.8

Mean 23.6

7.8 0.44 17.7

7.0 0.42 16.7

8.4 0.31 27.1

10.5 0.42 25.0

9.0 0.28 32.1

10.6 0.37 28.6

11.4 0.43 26.5

7.8 0.48 16.3

9.9 0.37 26.8

8.2 0.37 22.2

10.9 0.49 22.2

10.9 0.45 24.2

11.2 0.50 22.4

10.0 0.45 22.2

9.9 0.50 19.8

6.8

6.3

7.4

9.7

0.38 17.9

0.28 22.5

0.32 23.1

0.60 16.2

Mean 22.6

Species

External Green

volumetric Specific moisture

shrinkage1gravity2

content3

(percent) (percent)

1Green volume, ovendry weight basis.

2Green basis.

3Volumetric shrinkage divided by specific gravity.

8
Table 5 – Summary of green moisture contents based on data of Stamm (1964)

Type

Number

of

species Average

Mg (percent)

Standard

deviation Minimum Maximum

All softwoods 54 26.1 5.1 16.2 40.3

All in-grade softwoods

except cedar’

29 28.8 4.3 21.8 40.3

All in-grade softwoods

All in-grade woods

(including hardwoods)

34 28.0 4.4 21.7 40.3

39 28.8 4.7 21.7 40.3 

 9

1

Green (1983).
Table 6 – Predicted (eqs. (12) and (13)) and actual dimensions for Douglas Fir lumber based on average values from

Aplin et al. (1985)

Nominal

size (in) Grade

Moisture

content

(percent) Measured value (M, in) Predicted (P, in)

Thickness Width Thickness Width

percent)

Thickness Width

2 by 4 Select

Structural

No. 2

No. 3

2 by 6 Select

Structural

No. 2

No. 3

2 by 8 Select

Structural

No. 2

No. 3

67.0 1.576 3.576

20.4 1.558 3.524

15.8 1.540 3.476

10.2 1.527 3.441

69.9 1.598 3.577

19.3 1.554 3.516

15.6 1.540 3.484

10.2 1.531 3.443

80.1 1.575 3.575

21.7 1.565 3.534

15.9 1.550 3.494

10.2 1.535 3.448

66.0 1.562 5.636

18.6 1.544 5.528

14.3 1.527 5.458

11.0 1.517 5.412

76.1 1.571 5.651

19.0 1.553 5.547

14.6 1.533 5.493

10.8 1.528 5.434

76.2 1.569 5.630

19.1 1.554 5.558

14.4 1.537 5.488

10.7 1.520 5.428

56.4 1.580 7.545

18.7 1.557 7.415

14.9 1.545 7.343

10.2 1.529 7.242

62.4 1.579 7.524

18.6 1.552 7.409

14.5 1.547 7.336

10.2 1.530 7.269

69.0 1.574 7.521

17.8 1.552 7.389

14.5 1.546 7.347

10.3 1.529 7.264

– – – –

1.546 3.517 -0.8 -0.2

1.532 3.482 -0.5 0.2

1.517 3.439 -0.7 -0.1

– –

1.553 3.510

1.543 3.481

1.527 3.440

–

-0.1

0.2

-0.3

–

-0.2

-0.1

-0.1

– – – –

1.557 3.526 -0.5 -0.2

1.541 3.482 -0.6 -0.3

1.524 3.438 -0.7 -0.3

– – – –

1.535 5.522 -0.6 -0.1

1.523 5.470 -0.3 -0.2

1.514 5.430 0.2 0.3

– –

1.545 5.541

1.533 5.488

1.522 5.442

–

-0.5

0

-0.4

–

-0.1

-0.1

0.1

– – – –

1.544 5.522 -0.6 -0.6

1.530 5.465 -0.5 -0.4

1.520 5.420 0 -0.1

– –

1.553 7.394

1.543 7.332

1.529 7.256

–

-0.3

-0.1

0

–

-0.3

-0.1

0.2

– –

1.552 7.372

1.540 7.305

1.528 7.236

–

0

-0.5

-0.1

–

-0.5

-0.4

-0.5

– – – –

1.545 7.356 -0.5 -0.4

1.536 7.302 -0.6 -0.6

1.524 7.234 -0.3 -0.4

1 0
Table 7 – Shrinkage coefficients from Covington and

Fewell (1975)

Species

Average shrinkage

coefficient C

Thickness Width

Redwood-whitewood 0.00257 0.00196

Western hemlock 0.00207 0.00214

Western white spruce 0.00220 0.00164

Table 8 – Comparison of dry-green ratios predicted by this study and those determined by

Covington and Fewell (1975)

Dry-green ratio (15 and 28 percent)

Species Thickness Width

Equation Equation Equation Equation

(13) (19) (12) (19)

European redwood-whitewood 0.9765 0.9666 0.9719 0.9745

Canadian hemlock 0.9765 0.9731 0.9719 0.9722

Canadian white spruce 0.9765 0.9714 0.9719 0.9787

Table 9 – Average shrinkage to 15-percent moisture content

(Wood and Soltis 1964)

Species

Douglas-fir

Western hemlock

Southern Pine

Average

Shrinkage

in width

(percent)

2.7

3.1

2.5

2.8

Shrinkage

in thickness

(percent)

2.2

2.3

2.9

2.5

2.2-1/89

11