Vertical spacing.

TM 38-400/NAVSUP PUB 572/AFMAN 23-210 MCO 4450.14/DLAM 4145.12

from the weather by adequate roofing. Roofing should

(3) Spacing of storage rows. Generally, at

be placed on the top draft and lashed down prior to

machine-stacked lumber yards there are no rear aisles,

placing the draft on the stack. A good roof always has

and spaces between the ends of the stacks are provided

been considered an essential feature of good air-drying

by spacing the rows. Spaces between rows of unitized

practice. A roof shields the stack from direct sunshine

lumber stacks vary from 2 to 3 feet in air-drying yards.

and precipitation, particularly the upper lumber courses,

Here also, it is not feasible to recommend an optimum

and to a lesser extent, the lower part of the stack.

spacing, but a spacing of 2 to 3 feet should be sufficient

Without a roof, the upper courses of lumber become

at stack ends to induce sufficient air currents between,

warped and checked, and rain is permitted to penetrate

through, and under the stacks to carry off moisture

the stack from the top or to drive in from the ends and

saturated air.

sides. A leaky roof will afford protection against direct

b. Vertical spacing.

sunshine but will permit water to wet the upper lumber

(1) Space required for use of forklift trucks.

courses and to penetrate the stack. To afford maximum

Spacers (dunnage) used in connection with the stacking

protection, a roof should project 12 to 18 inches at the

of lumber in drafts may be considered to be a part of the

ends of the stack and approximately 6 inches over the

stack foundation. When a draft of lumber is picked up

sides.

or set down, space for the insertion or removal of the

(1) Staggered board protection method. A

forks must be provided. Usually, this space is about 6

good low-cost roof, adequate for lower grades of lumber,

inches wide in slope stacked lumber, but may be

dimension stock, or lumber which will not remain in

narrower when the new model of forklift truck is used.

storage for a long period of time, can be built into each

These newer trucks have an arrangement for tilting the

draft as it is formed. To form this roof, one piece of

forks through an angle of 5 degrees for picking drafts

lumber is left out of the top layer and the remaining

from sloped stacks of lumber; however, tilting

lumber is staggered or placed so that each board covers

mechanism is not required if 6-inch spacing is

an opening between the tiers of lumber (fig 5-13). Thus,

maintained between drafts.

moisture is prevented from entering the draft and the

(2) Placing of spacers. When building a

two layers of each unit load becomes the roof. Since

stack of prepared drafts of lumber, the spacers are

drafts are built with a 15/s-inch pitch per foot of height

placed (directly over the stickers) on top of each draft or

and stored on foundations which provide 1 inch of slope

on top of the upper one when handling two at a time,

per lineal foot, this roof will afford good protection for

before stacking. Of course, this need not be done with

normal storage requirements. This roof does not afford

the lower draft of the stack where the top is reached

quite as much protection from the weather as roofs with

readily from the ground. When the stack is completed,

extended ends and sides. This is compensated for in

the channels caused by the placement of these spacers

several ways (e.g., lumber is always roofed and cannot

provide additional area for air passage through the

be accidentally left uncovered; permanent roofs are not

stack.

Thus, these passages conceivably may

maintained or stored when not in use; man-hours are not

counteract the disadvantages of the relatively high

expended in subsequent roofing operations; and, as unit

stacks usually found in mechanized lumber yards.

loads are bound, additional lashings are not required to

c. Roofing protection for stacks. Lumber, which

keep roofs in place).

cannot be stored undercover, should be protected

5-14