DESIGN, 

PERFORMANCE, 

AND INSTALLATION 

OF A PRESS-LAM 

BASEMENT BEAM 

IN A FACTORY-BUILT 

HOUSE 

RESEARCH 

PAPER 

FPL 316 

FOREST PRODUCTS LABORATORY 

FOREST SERVICE 

U.S. DEPARTMENT OF AGRICULTURE 

MADISON, WIS. 

1978 
Abstract 

Press-Lam and other parallel-laminatedveneer products exhibit distinct advantages 

when utilized in applications that require welldefined material properties. 

A Press-Lam basement beam was designed and manufactured for a model prebuilt 

house, Design stresses were determined in 

conjunction with another Press-Lam study. The 

finished beam was installed by a regular construction crew using no special equipment or 

techniques. 

Performance of this beam is expected to 

be comparable to other design alternatives, 

and to exceed design requirements for the life 

of the structure. 
DESIGN, PERFORMANCE, 

AND INSTALLATION OF 

A PRESS-LAM BASEMENT BEAM 

IN A FACTORY-BUILT HOUSE1 

By

J. A. YOUNGQUIST, 

D. S. GROMALA, 

R. W. JOKERST, 

R. C. MOODY, 

and 

J. L. TSCHERNITZ 

Forest Products Laboratory,2 Forest Service 

U.S. Department of Agriculture 

Introduction 

As supplies of large, high-quality sawtimber decline, additional raw material supplies 

must be sought for the manufacture of structural-size timbers for items such as basement 

beams. Small or low-grade logs can fill that demand if they can be processed into engineered 

wood products. Press-Lam, a process developed at the Forest Products Laboratory (FPL). 

offers that potential. 

Press-Lam is a parallel-laminated-veneer 

product, made by peeling logs on a veneer 

lathe, drying the veneer in a heated press, applying an adhesive, layering and pressing again 

into a continuous sheet of laminated wood. Research at FPL has examined the effects of veneer peeling, press drying, and laminating on 

product performance (4)3. Other aspects of 

PLV research have been explored by the USDA 

Forest Service's Southern Forest Experiment 

Station and by the Canadian Forest Products 

Laboratories. 

1Research conducted in cooperation with Wausau Homes, 

Inc., Wausau, Wis. 2Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 

3Numbers in parentheses refer to literature cited at the end 

of this report. 

Because the physical dimensions of the 

continuous sheets are limited only by production equipment, sheets can be ripped and 

cross-cut to meet desired end-product requirements. Extensive test programs at FPL on experimentally produced parallel-laminated veneer have established that the mechanical 

properties of this product can be closely controlled. Markets for which PLV may be well 

suited include mobile home center beams and 

truss chords, components for manufactured 

housing, door rails and stiles, tension laminations for glulam beams, and roof decking support systems. 

The beam project described in this report 

covers one of four chosen FPL demonstration 

uses of parallel-laminated veneer for structural 

and/or specialty products. Other reported 

demonstration uses include railroad ties (7), 

electrical distribution crossarms (8), and bridge 

timbers and decking (9). 

To demonstrate the feasibility of incorporating Press-Lam into a house design, the FPL 

entered into a cooperative agreement with 

Wausau Homes, Incorporated, of Wausau, 

Wis., to supply a Press-Lam basement beam for 

installation and use in a prebuilt house. 
Preparation of Material for Beam 

Peelable Coast Douglas-fir No. 2 sawlogs 

were shipped to the Forest Products Laboratory, cut to 52-inch bolt lengths, and rotary 

peeled on a 4-foot lathe to a thickness of 0.42 

inch. This veneer was then clipped to 21-inch 

widths and press dried at 375° F at 50 psi to an 

average moisture content of 15 percent. Drying 

time was either 5.5 minutes or 11 minutes, depending upon whether sapwood or heartwood 

was being processed. Because the drying 

press was not in the same building as the laminating equipment used in producing this material, the dried veneer had to be reheated in a 

conventional veneer drier prior to glue application and lamination. The reheating process 

reduced the moisture content of the veneer to 

about 11 percent. This press-dried veneer was 

then assembled into a continuous sheet of 4­

ply step-pressed dimension stock, using a 

phenol resorcinol adhesive. Veneer placement 

was staggered in each layer to allow for a 12­

inch spacing between adjacent butt joints. The 

wood was at a minimum temperature of 200° F 

prior to adhesive application and was laminated using pressures of 150 psi for approximately 6 minutes. Dimension material, 1 1⁄2 by 20 

inches in cross-section was then cut to lengths 

of 21 feet. Both the length and width of these 

Press-Lam components were constrained by 

laboratory equipment limitations. 

Dimension boards were abrasive planed 

and cold-laminated into structural-size timbers 

for use in concurrent studies aimed at determining the properties of large Press-Lam members 

Establishing Design Stresses 

Eighteen beams were loaded to failure (9) 

in two-point edgewise bending in accordance 

with ASTM D 198 (1). Load and midspan deflection were monitored continuously to failure. 

Test beams, 41⁄2 inches wide by 20 inches deep, 

were tested on spans ranging from 17.5 to 19 

feet. The average modulus of rupture (MOR) 

was 5,450 psi, with a coefficient of variation of 

about 9 percent. 

An additional 18 beams were similarly 

loaded to evaluate their moduli of elasticity 

(MOE). The average MOE for the 36 beams was 

1.7 million psi, with a coefficient of variation of 

less than 7 percent. 

The allowable bending stress was derived 

by methods outlined in ASTM D 2915 (2). The 

near-minimum strength of the population (5th 

percentile) was divided by a factor of 2.1 to account for long-term loading and the possibility 

of accidental overloading of the member. The 

resultant allowable bending stress was 2,200 

psi. This value was then multiplied by factors to 

account for duration of load (1.15) and size effects (1.06) to arrive at the final allowable stress 

of 2,680 psi. Deflection calculations were 

based on the average MOE (1.7 million psi), as 

specified in the National Design Specification 

(NDS) (3).

Because none of the test beams failed in 

shear, it is difficult to assess the allowable 

shear stress for these members. The average 

shear stress at failure was calculated to be 330 

psi. If these beams had failed in shear, the design shear stress would be 130 psi. This value 

was chosen to represent a conservative estimate of allowable shear stress. 

Basement Beam Design 

Because the Press-Lam basement beam 

was to be installed as a minor modification in a 

factory-designed house, its dimensions were 

necessarily made compatible with the existing 

design (fig. 1). The primary constraint from a 

design standpoint was that the beam depth 

could not exceed 12 inches. This restriction 

produced a beam that was less material-efficient than a deeper member. 

Design Requirements 

The design loadings currently employed by 

the commercial designers involved in this project are: 

Floor Load: 40 psf live; 8 psf dead 

Roof Load: 30 psf live; 8 psf dead 

Maximum allowabledeflection is 1/240th of the 

span under full load and 1/360th of the span 

under live load only. 

The standard basement beam for this 

model would be either four glue-nailed 2 by 8's 

over five intermediate supports (fig. 2a), or a 

steel beam, 8 inches deep, over three interme2 
 
Figure 1.–Basement floor plan of test house. 

M 146 565 

diate supports (fig. 2b). The Press-Lam beam 

was intended to provide an alternative to !he 

steel beam when three intermediate supports 

are specified (fig. 2c). 

of the column supports, and assurance of the 

adequacy of the joint design was required. As 

outlined in the appendix, the joint was designed 

such that bending stresses in a ply, rather than 

Design Calculations 

the torsional shear stresses in the lap, would be 

critical. 

A beam section 51⁄2 inches wide by 10 

The final beam was designed to be 6 

inches wide by 12 inches deep. Two sections 

inches deep by 91⁄2 feet long with a lap joint at 

midspan was tested to examine its failure 

were manufactured. Beam sections A and 6 

(fig. 3) were field-spliced over a support with an 

mode. It was loaded in center point bending on 

a 9-foot span. The specimen failed in a bending 

array of nails. These nails provide little transfer mode, similar to other Press-Lam members with 

of bending moment at small joint rotations. For 

this reason, the joint over the column at R3 (fig. 

2) was considered to be nonrigid and was assumed to be a simple support for design purposes. However, a rigid structural joint was provided over the column adjacent to the longest 

span (R4, fig. 2) to minimize deflections on the 

long span. The final beam dimensions and lapjoint configuration are shown in figure 3. 

butt joints. The MOR on the gross section was 

3,150 psi, and the MOE was 2.0 x 106 psi. Assuming that the outer four plies (the last leg of 

the lap joint) cannot transmit bending stresses, 

the MOR on the net section becomes 4,200 psi. 

This value is 23 percent less than the mean 

strength of 5,450 psi found for the beams without a lap joint. 

Even with this reduction in strength the 

An evaluation of the design strength and joint exhibited nearly twice the required design 

stiffness of the three beams shown in figure 2 is 

given in the appendix. 

strength and failed in a bending mode. Based 

on these considerations, the structural lap joint 

Verification of Lap-Joint Design 

As noted, beam section B (fig. 3) was dewas considered adequate. 

The measured MOE in this test also served 

to verify the hypothesis that butt or lap joints 

did not reduce the gross section bending stiffsigned to be structurally continuous over one ness. 

3 
Figure 2.–Three typical basement beam designs. 
 

M 146 566 
 

Figure 3.–Plan view of beam section dimensions and lap joint configuration. 
 

M 146 564 
 

4 
 
Installation of Basement Beam 

The beam was delivered in January, 1977, 

to the Wausau Homes plant in Wausau. Wis., in 

two sections--section A measuring 18 feet, 

101⁄2 inches; section B measuring 28 feet, 41⁄2 

inches. Each had one staggered end (fig. 3) to 

allow for the field splice. 

At the erection site near Wausau, the two 

sections of the beam were removed from the 

truck and placed at ground level on the edge of 

the foundation. The sections were connected 

with an array of nails. The top course of the 

foundation served as a leveling device to align 

the splice. When the two pieces were joined, 

the finished beam measured a nominal 6 inches 

wide by 12 inches deep by 47 feet, 61⁄2 inches 

long. A deflection line was installed on the 

beam at that time. The beam was then installed 

in precut pockets in the concrete block foundation (fig. 4). Steel shims were used to level 

the beam. Although the construction crew had 

had no prior experience with beams of this 

length, no erection problems were encountered. 

As various housing components were assembled on the structure, beam deflection 

measurements were taken. With all of the exterior and interior walls in place, the floor panels 

secured, and the roof panels in place, no beam 

deflection was detectable. The owner's impressions of overall beam performance will be monitored periodically. 

Figure 4.–Press-Lam beam installed in test house. 

M 145 290-3A 

5 
Summary 

A main basement beam, manufactured of 

Press-Lam, was designed for a specific loading 

configuration and installed as the main supporting member for a factory-built house. The 

beam was installed by the regular construction 

crew using no special equipment or techniques. The structural continuity of the PressLam beam provides greater effective span stiffness, resulting in a larger column-free basement area than is possible using the standard 

glue-nailed beams. In designs where the additional beam depth can be tolerated, Press-Lam 

can be used as an alternative to a steel beam. 

LiteratureCited 

1. American Society for Testing and Materials. 

1967. 	 Standard tests of timbers in structural sizes. ASTM Stand. Desig. D 198­

67. ASTM, Philadelphia, Penn. 

2. American Society for Testing and Materials. 

1974. 	 Evaluating allowable properties for 

grades of structural lumber. ASTM 

Stand. Desig. D 2915-74. ASTM, Philadelphia, Penn. 

3. National Forest Products Association. 

1977. 	 National design specification for 

wood construction. NFPA, Washington, 

D.C. 

4. Schaffer, E. L., R. W. Jokerst, R. C. Moody, 

C. C. Peters, J. L. Tschernitz, and J. J. Zahn. 

1977. 	 Press-Lam: Progress in technical 

development of laminated veneer structural products. USDA For. Serv. Res. 

Pap. FPL 279. For. Prod. Lab., Madison, 

Wis. 

5. Schaffer, E. L., J. L. Tschernitz, C. C. Peters, 

R. C. Moody, R. W. Jokerst, and J. J. Zahn. 

1972. 	 Feasibility of producing a high-yield 

laminated structural product: General 

summary. USDA For. Serv. Res. Pap. 

FPL 175. For. Prod. Lab., Madison, Wis. 

6. Seely, F. B., and J. O. Smith. 

1932. 	 Advanced mechanics of materials. 

John Wiley and Sons, Inc., New York. 

7. 	 Tschernitz, J. L., E. L. Schaffer, R. C. Moody, 

R. W. Jokerst. D. S Gromala, C. C. Peters, 

and W. T. Henry. 

1979. Hardwood Press-Lam crossties: 

Processing and performance. USDA 

For. Serv. Res. Pap. FPL 313. For. Prod. 

Lab., Madison, Wis. 

8. Youngquist, John, Frank Brey, Joseph 

Jung. 

1977, 	 Structural feasibility of parallel-laminated veneer crossarms. USDA For. 

Serv. Res. Pap. FPL 303. For. Prod. 

Lab., Madison, Wis. 

9. Youngquist, J. A., D. S. Gromala, R. W. 

Jokerst, R. C. Moody, and J. L. Tschernitz. 

1978. The design. fabrication, testing, and 

installation of a Press-Lam bridge. 

USDA For. Serv. Res. Pap. FPL 332. 

For. Prod. Lab., Madison, Wis. 

6 
Appendix 

Bending Stresses and Deflections 

The design of this house was based on a 

24-foot bay width (dimension perpendicular to 

the beam axis). Half of this width contributes 

load to the beam, while the rest is distributed 

between the foundation walls. 

Thus, design loads convert to uniform distributed loads as follows: 

Floor: 40 psf x 12 ft = 480 Ib/linear ft, 

live 

8 psf x 12 ft = 96 Ib/linear ft, 

dead 

Roof: 30 psf x 12 ft = 360 Ib/linear ft, 

live 

8 psf x 12 ft = 96 Ib/linear ft, 

dead 

The 18-foot, 101⁄2-inchspan nearest the garage is subject to floor loads only, as a ridge 

beam across the living room carries the roof 

load above this span. All other spans are beneath a load-bearing partition and carry both 

floor and roof loads. 

NDS permits a 15 percent increase in nominal design stresses when designing for snow 

loads. The snow load is 35 percent of the total 

load for this design, thus it is the critical design 

case. 

Analyses were performed on the three 

beam configurations with the following 

assumptions: 

(a) Glue-nailed 2 by 8's: 

Allowable bending stress = 

1650 psi4 

Increase for snow duration 

= 1.15 x 1650 = 1900 psi 

Modulus of elasticity (MOE) 

= 1.7 million psi 

All spans simply supported. 

(b) 8-inch wide-flange steel beam: 

Yield stress (fy) = 36,000 psi 

Allowable bending stress = 

0.6 x fy = 21,600 psi 

MOE = 29 million psi. 

4No. 2 Douglas-fir. repetitive use. 

(c) 12-inch-deep Press-Lam beam: 

Allowable bending stress = 

2330 psi 

Increase for snow duration 

= 1.15 x 2330 = 2680 psi 

MOE = 1.7 million psi. 

Conventional engineering mechanics formulae were used to analyze the beams. Maximum bending stresses and deflections expressed as a fraction of the allowable are 

shown for the three design alternatives in figure 

A1. For each beam section, stresses and deflections shown are for the most critical loading 

combination. 

Design of Lap Joint 

The lap joint was designed such that the 

theoretical strength of a single glueline with an 

area of b (lap length) times h (beam depth) 

would transmit bending stresses equal to the 

moment capacity of a single leg of the joint (4 

plies). These stresses are transmitted through 

torsional shear in the joint. 

Both bending and torsional shear stresses 

are linear functions of the applied moment at 

the joint: 

s

where 

max = maximum bending 

stress (psi) 

Mmax = maximum bending 

moment (inch-pounds) 

S = section modulus 

(in.3) 

= th2 

6 

t = beam width (in.) 

h = beam depth (in.) 

b = lap length (in.) 

t max = maximum torsional 

shear stress (psi) 

a = factor tabulated in mechanics text dependent upon 

joint geometry. 

It was assumed that the ratio of bending 

strength to shear strength of this Press-Lam 

material is about 12 to 1, i.e., 

smax = 12 tmax 

(2A) 

7 
1 

Then, substituting values of a tabulated in smax = M 21,660 lb-ft = 2,400 psi max 

mechanics of materials textbooks (e.g., 6), and S 108 in.3 

iterating yields (4A)

bmin = 15 in. 

(3A) 

Assuming that one leg of the joint (4 plies) 

is ineffective in resisting bending stresses at 

the joint, the bending stress is 

This stress is less than the allowable value 

previously derived, and the lap length of 15 

inches is adequate. 

Figure A1.–Normalized stresses ( s ) and deflections ( d ) for 3 beam configurations expressed as a 

percentage of the allowable. 

M 146 567 

8 US GOVERNMENT PRINTING OFFICE 1978-750126/36