AQ DEPARTMENT BULLETIN 1425, U. 8S. DEPT, OF AGRICULTURE 
chimney 8 inches wide at the top and 22 inches wide at the bottom. 
Random-width 6/4 shop and select western yellow pine stock was 
used in all piles. Pile construction without chimneys resulted in a 
total degrade of 24.6 per cent, as compared with 16.6 per cent from 
the two-chimney method and 9.2 per cent from the use of the flared 
chimney. Most of the depreciation in all piles resulted from stain, 
the rate of drying being fastest in the flared-chimney pile and slowest 
in the no-chimney pile. 
The results obtainable from the common 12-inch center chimney 
were compared with those from piling with five 7-inch chimneys 
evenly distributed across the pile and the boards on a course placed 
approximately solid within the six vertical sections of stock. 
Random-width 4/4 select western white pine stock was used. The 
five-chimney method resulted in 10 per cent less stain development, 
a 3 per cent smaller degrade from stain, and only halt the loss from 
season check. The actual degrade loss was $2.75 per thousand less 
by the five-chimney method, stock reached the air-dry condition two 
weeks earlier, and the final moisture content was shghtly lower. 
As is true with all phases of pile construction, the use of chimneys 
or vents must be adapted to the situation at each plant. It is pos- 
sible, however, to set up some very definite principles as a guide. In 
piles of even-width stock the use of chimneys is not as effective as 
is an equivalent increase in the width of the unbroken vertical fiues 
between the uniformly spaced boards. In piling random-width stock, 
a single straight center chimney at least 12 inches in width is an 
improvement over no chimney; but less piling space is sacrificed and 
much more efficient seasoning is obtained by the use of three or more 
smaller chimneys evenly distributed across the width of the pile. 
Where three or more uniform chimneys are impracticable, as is often 
the case with very wide shop and select grades of California pine, 
a single flared chimney at least 22 inches wide at the bottom will 
prove more effective than a single straight chimney. 
It should be realized that the use of chimneys is only one of sev- 
eral means to obtain more efficient drying within the lumber pile. 
If sluggish drying is to be overcome, any system of chimneys must 
be supplemented by one or more of the other means. 
ROOFS 
A good pile covering improves seasoning by protecting the stock 
from rain and snow and from full exposure to the direct rays of the 
sun. Some operators believe that, at least during seasons of light 
precipitation, lumber seasons more rapidly in unroofed piles. What- 
ever slight advantage there may be in this practice is, however, more 
than offset by its disadvantages. In seasons of sparse rainfall, when 
the most rapid drying can be expected in unroofed piles, the direct 
exposure to the sun and the consequent excessive rate of drying 
cause heavy depreciation from cup, warp, twist, and check in the 
upper portion of the pile. At no time is alternate drying and wet- 
ting of stock an aid to seasoning; generally it only invites 
depreciation. 
Stock is commonly roofed with itself or with special roof boards. 
Special roofing has definite advantages. It is possible to utilize 
material of the size best adapted to the purpose and of the species 

