Layout of a Timber Drying Yard

The following are important principles for the design and efficient functioning of an area used to air season timber (a “timber drying yard”).

Where possible:

· Good drainage of a timber drying yard is important – so a slight sloping of the yard is desirable.

· The timber drying yard and its stock should be located well away from ponds and rivers which elevate the relative humidity.· A good yard surface is very desirable: soft, damp yard surfaces (mud etc.) must be avoided. This is to reduce the possibility of fungi developing and infecting the drying stock. Tarmac or concrete surfaces of the yard are ideal, but cinders or even well -compacted earth are acceptable.

· Obstructions impeding air movement should be avoided. Thus hedges might be removed and stacks should not be constructed in the lee of buildings.

· Good "housekeeping" in the timber drying yard helps avoid contamination of stock by fungi and insects and is also sensible from a point of view of health and safety of workers.

· It is important to ensure that suitable fire breaks are provided to contain fires.

· In some climates it is necessary to retard the rate of drying as too rapid drying can lead to various forms of drying defects. Thus water sprays might be used to moisten the timber and roofs constructed to shade stacks from the sun (thatch etc. can be used – but NOT corrugated iron, which can get very hot).

· The short axis of a timber drying yard should be parallel to the prevailing wind so that the wind can blow through the maximum number of stacks of timber and across the width of the boards:

Diagram showing two timber stacks aligned with the boards' long axes perpendicular to the prevailing wind.

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Diagram showing two timber stacks aligned with the boards' long axes perpendicular to the prevailing wind. The small wooden “stickers” (“sticks”) separating the layers of timber pieces are aligned parallel to the prevailing wind so as not to impede air flow through the stack.

For valuable stock, stacks might be build inside specially designed “drying sheds” (having e.g. movable louvres to control air flow). Simple “Dutch barns” can also be used – it is important however that such sheds are not overcrowded – this would be a false economy as relatively easy access is necessary to remove individual stacks when required.

Note that large diameter logs are best sawn ‘green' (little or no drying has occurred). However if they are stored for a long time a log may 'end-split':-

To avoid end-splitting it might be tempting to nail metal sheets on the ends of the logs: this is in fact bad practice as the restraining metal will cause damage to the wood as it shrinks. It is much more preferable to inhibit drying of the logs by painting their ends with a flexible bituminous or rubber based paint.

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Contents

Reasons to Dry Timber: An Introduction to Timber Drying

Timber Drying - Fundamentals Concepts and Definitions

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

Kiln Drying of Timber

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

Solar Kilns for Drying Timber

Drying Defects in Sawn Timber

Case Hardening of Timber

Avoiding Case Hardening by Monitoring the Drying of Timber. Also Collapse & Staining of Timber