RTI

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 products^a
Softwood^b	Thousand cubic feet	15.500
Hardwood^c	Thousand cubic feet	20.000

Softwood^b	Cord (80 cubic feet)	1.400
Hardwood^c	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. ^aLogs, bolts, pulpwood, fuelwood, and miscellaneous industrial roundwood. ^bAt 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 ft² 3/8 per			Nonstructural panel use,^b ft² 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. ^aSoftwood plywood, waferboard, OSB, composite board. ^bHardwood 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	ft³ panel per MSF 3/8	MSF 3/8 per ft³panel	Log ft³ per MSF 3/8	SF 3/8 per log ft³ VRF	Log ft³ per panel ft³	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 ft³log 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 ft³	log ft³ per MSF 3/8	SF 3/8 per log ft³	log ft³ per panel ft³	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	NA^c
Insulation board	31.25	32	14.3	69.93	0.46^b	NA^c
Hardboard	31.25	32	45.9	21.79	1.47	NA^c

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. ^aFinished panel. ^bThat is, 0.46 ft³ of log is expanded to 1 ft³ of panel. ^cCannot be expressed due to panel densification.

2. OSB/Wafterboard recovery factors by region, 1985

	Region	ft³3/8 product per ft³log input

	North	17.9

	South	16.9

G. Wood pulp factors:

Appendix II