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Appendix II

Conversion Factors for Wood Products

The conversion factors in this appendix are those used in the USFS publication, An Analysis of the Timber Situation in the United States: 1989-2040 (Haynes 1990). They are a weighted average of the following influences:  (1) mix of species used, (2) various states of manufactured products as they enter commerce, (3) regional differences in production quantity, and (4) various manufacturing technologies.

A.  Average product weights.

     

Weight of wood

 
     

per standard unit

 
 

Product

Standard unit

(short tons)

 
 

Roundwood productsa

     
 

    Softwoodb

Thousand cubic feet

              15.500

 
 

    Hardwoodc

Thousand cubic feet

              20.000

 
         
 

    Softwoodb

Cord (80 cubic feet)

                1.400

 
 

    Hardwoodc

Cord (80 cubic feet)

                1.600

 
         
 

Lumber

     
 

    Softwood          

Thousand board feet                                         

                0.974

 
 

    Hardwood

Thousand board feet                                         

                1.680

 
         
 

Structural panels

 

                          

 
 

    Softwood plywood

Thousand square feet, 3/8 inch basis

                0.544

 
 

    Waferboard and OSB

Thousand square feet, 3/8 inch basis

                0.866

 
         
 

Nonstructural panels

     
 

    Hardboard

Thousand square feet, 3/8 inch basis

                1.140

 
 

    Insulation board

Thousand square feet, 3/8 inch basis

                0.275

 
 

    Particleboard

Thousand square feet, 3/8 inch basis

                0.289

 
 

    Hardwood plywood

Thousand square feet, 3/8 inch basis

                0.657

 
Source:  Haynes (1990, Table B-7).

Note:
 Lumber weights are weighted averages for the species and volumes of production as reported by the Bureau of the Census for 1986. Average weights per thousand board feet, at 15% moisture content (USFS 1987), were used to convert volumes, by species, to tons. The weight of dressed lumber was used for softwoods because the product is ordinarily sold as surfaced-dry, while rough-dry hardwood lumber weights were used because this product is ordinarily marketed in that form.

Plywood weights are averages for the species and volumes of production for 1986. Average weights per cubic foot (15% moisture content) were used to convert volume, by species, to tons at 31.25 cubic feet per thousand square feet, 3/8 inch basis. The weight of hardwood plywood was adjusted for a raw material mix of 62% hardwood and 38% softwood (Haynes, 1990, Table B-6).

Particleboard weight is based  on a bone-dry weight of 46 pounds per cubic foot of product, and is adjusted to air-dry moisture content and to delete the weight of resins, waxes, and additives (8.5% of bone-dry weight). Hardboard and insulating board weights are those reported by the Bureau of the Census in 1986, with the weights of resins, waxes, and other additives deleted.

a
Logs, bolts, pulpwood, fuelwood, and miscellaneous industrial roundwood.

b
At 35 pounds per cubic foot, air dry.

cAt 40 pounds per cubic foot, air dry.



B. 
Volume per product unit factors.

Product

Units

Value

 

Cord

ft3solid per cord

79.2

 
 

Cord of pulpwood per ton pulp

1.50

 

Rail  crosstie

Board feet per tie

40

 
 

ft3 per tie

3.5

 
 

m3 per tie

0.10

 

Rail bridge/switch tie

board feet per tie

63

 
 

ft3 per tie

5.25

 
 

m3 per tie

0.15

 

Pallet

Board feet lumber per pallet

17

 
 

ft2(3/8 basis) structural panel per pallet

0.86

 
 

ft2 (3/8 basis) nonstructural panel per pallet

0.50

 

Pulp

Ton of wood pulp per ton of paper and paperboard

1.02

 
 

Cord of pulpwood per ton of wood pulp

1.50

 

C.  Use of wood products in new U.S. housing by product and type of unit, 1986.

 

Average        area

 

 Lumber use, BF per

    Structural panel use,a
          ft
2 3/8 per

  Nonstructural panel use,b
            ft
2 3/8 per

 

Type of unit

(ft2)

Unit

ft2

Unit

ft2

Unit

ft2

 

Single family

1,825

12,975

7.11

6,770

3.71

2,755

1.51

 
                 

Multifamily

 911

 4,720

5.18

2,505

2.75

 850

0.93

 
                 

Mobile home

1,110

 4,340

3.91

1,610

1.45

3,805

3.43

 

Combined

1,460

9,419

6.45

4,851

3.32

2,296

1.57

 
Source:  Haynes (1990, Tables 1, 2, and calculated from data on pp. 9-10).

Note:
  Volumes include allowances for on-site and manufacturing waste.

a
Softwood plywood, waferboard, OSB, composite board.

b
Hardwood plywood, hardboard, insulation board, particleboard, MDF.



D. 
Lumber factors:

1.  Composite national averages

       

ft3lumber per

ft3log per

ft3log per

Lumber

BFFR

LRF

CRR

MBF lumber

MBF lumber

ft3lumber

 

Softwood

16.67

6.44

0.362

60.00

155.1

2.76

Hardwood

12.00

5.26

0.499

83.33

189.9

2.00

 
See Chapter 4 for definition of BFFR, LRF, and CRR.

Note: 
The softwood CRR is lower than that for hardwood since most softwood lumber leaves the sawmill surfaced, dried, or both whereas most
hardwood lumber leaves the sawmill rough green.


2.  Lumber recovery factor (LRF) by region, 1985

 

BF lumber per ft3 log input

 

Region

Softwood

Hardwood

 

          North

          South

          Rocky Mountains

          Pacific Coast:   West

                                     East

          Pacific Southwest

NA

6.02

6.80

7.87

6.33

6.80

NA

NA

NA

NA

NA

NA

 

E. Plywood factors:

1.  Composite national averages



Lumber


ft
3 panel per
MSF 3/8


MSF 3/8 per
ft
3panel


Log ft
3 per
MSF 3/8

SF 3/8 per
log ft
3
VRF


Log ft
3 per
panel ft
3



CRR %
a

 

Softwood

31.25

32

71.1

14.1

2.25

44.5

Hardwood

31.25

32

64.2

15.6

2.06

48.6

 
aFinished panel. See Chapter 5 for discussion of plywood terminology.



2.  Veneer recovery factor (VRF) by region, 1985

 

ft2 3/8 plywood per ft3 log input

 

Region

Softwood

Hardwood

 

          North
          South
          Rocky Mountains
          Pacific Coast:   West
                                     East
          Pacific Southwest

NA
13.9
14.3
14.5
17.2
14.3

NA
NA
NA
NA
NA
NA

 

F. Nonveneer panel factors:

1.  Composite national averages


Panel

ft3 per MSF
     3/8

MSF
3/8 per ft
3

log ft3 per MSF
3/8

SF 3/8 per
log ft
3

log ft3 per
panel ft
3


CRR %
a

 

OSB/waferboard

31.25

32

62.3

16.0

1.99

50.1

 

Particleboard

31.25

32

45.6

21.92

1.46

NAc

 

Insulation board

31.25

32

14.3

69.93

0.46b

NAc

 

Hardboard

31.25

32

45.9

21.79

1.47

NAc

 
Note:   While the term "log ft3" is used in the table to indicate that these factors reflect roundwood equivalent, in fact much of the raw material used by
these processes is by-product residues from other wood industries, not roundwood logs.      

a
Finished panel.      

b
That is, 0.46 ft3 of log is expanded  to 1 ft3 of panel.      

c
Cannot be expressed due to panel densification.



2.  OSB/Wafterboard recovery factors by region, 1985

 

Region

ft33/8 product per ft3 log input

 
 

North

17.9

 
       
 

South

16.9

 


G.
Wood pulp factors:


 
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