Much of the discussion below relating to the construction of “box” (or “flat”) stacked
(or “piled”) square-
The correct CONSTRUCTION and ORIENTATION of stacks of timber is very important as
it influences the air circulation, which is a significant determinator of the rate
and even-
Stacks of sawn timber should not be built directly on the ground but should be raised off the ground on bearers (or foundations) – usually of brick or concrete (but it should be ensured that lower boards in a stack are not damaged, by indentation, due to the resilience of such hard materials) or treated hardwoods (to avoid the possibility of fungal or insect infection). These stack foundations must lie all in same plane, so the boards are not caused to distort.
In some countries it is useful to be able to look underneath stacks of timber in the yard to check for evidence of insect attack – dust might be seen suggesting that termites are at work within the stack!
Stickers
These are the pieces of wood which are used to separate layers of pieces of timber in the stack so that air can gain intimate contact with the surfaces of all the boards.
The cross-
The stickers must be of a wood species that is softer than the stock being dried
as otherwise “sticker marks” will be left on the dried pieces of timber where the
stickers have embedded themselves into the board surfaces.The closeness of stickering
(i.e. how far apart they are – or how many stickers are used along the length of
the stack) can be used to control any distortion that the boards might sustain (“bow
etc – see later). Thus “close-
The closeness of stickering (i.e. how far apart they are – or how many stickers are
used along the length of the stack) can be used to control any distortion that the
boards might sustain (“bow etc – see later). Thus “close-
HOME
A well stickered stack (here ready to enter a kiln). Note the stickers are aligned vertically above each other.
The volume of timber comprising the numerous stickers that are required in a timber yard is considerable and it is sensible therefore to look after the stickers, protecting them from breakage etc.
"Close piling" – where no stickers are used (attempting to separate drying stock by using the boards themselves) is a poor technique as unacceptably large areas of the boards remain wet and prone to degrade.
A number of methods are used to stack square edged sawn timber, although some are uncommon nowadays:
· Flat (or box) piling: This is the commonest method. A rectangular “box” of boards is built up, usually less than 6 feet (2 metres) wide and less than 3 times as high (to reduce compression damage in lower boards and to ensure stack stability). Sometimes weights are used on the top of the stacks to reduce the possibility of distortion occurring in some species as they dry (e.g. elm, beech). These stacks might be built “by hand” (when it is important to ensure the principles of good stack construction are followed – see above) or in large mills “stickering machines” can be used at the end of the sawing line.
· “Crib” piling: Less common than the above. Sometimes used to stack dimensioned
stock. Not a good method. No stickers are used -
· Bristol piling: Used in the past to stack dry timber at a port as a ship is unloaded.
The “self-
· End and Cross Racking: Useful to achieve the fast, superficial drying of board surfaces where necessary to protect them from stain (sycamore is prone to a damaging stain if the board surfaces are not rapidly dried).
Uncommon methods of stacking timber. Left to right: Bristol stacking, end racking and cross racking.
Stacking square edged sawn timber
A number of methods are used to stack square edged sawn timber, although some are uncommon nowadays:
· Flat (or box) piling: This is the commonest method. A rectangular “box” of boards is built up, usually less than 6 feet (2 metres) wide and less than 3 times as high (to reduce compression damage in lower boards and to ensure stack stability). Sometimes weights are used on the top of the stacks to reduce the possibility of distortion occurring in some species as they dry (e.g. elm, beech). These stacks might be built “by hand” (when it is important to ensure the principles of good stack construction are followed – see above) or in large mills “stickering machines” can be used at the end of the sawing line.
· “Crib” piling: Less common than the above. Sometimes used to stack dimensioned
stock. Not a good method. No stickers are used -
· Bristol piling: Used in the past to stack dry timber at a port as a ship is unloaded.
The “self-
· End and Cross Racking: Useful to achieve the fast, superficial drying of board surfaces where necessary to protect them from stain (sycamore is prone to a damaging stain if the board surfaces are not rapidly dried).
Reasons to Dry Timber: An Introduction to Timber Drying
Timber Drying -
Factors controlling the Drying of Wood
The Structures of Softwoods and Hardwoods and their effect on Wood Drying
An Introduction to the Air Seasoning of Timber
Layout of a Timber Drying Yard
Design of Stacks in the Timber Drying Yard
Types of Kiln Drying Equipment
Benefits of Kiln Dried Timber production compared to Air Seasoning Timber
Using a Dehumidifier to Dry Wood
High Temperature Timber Drying
Avoiding Case Hardening by Monitoring the Drying of Timber. Also Collapse & Staining of Timber