Wood is a fibrous organic material the properties of which will vary with the tree from which it was taken, the geographical (and geological) location in which it grew and its greenwood moisture content, which can vary between 10% and >100% of the [solid] cellular material. The properties listed in Woods are average values based upon oven-dry condition (12% moisture content).
All woods comprise between 40% to 50% cellulose. However, lignin normally varies between 15% to 35% and hemicellulose varies between 20% to 35% dependent upon wood type and origin. All woods contain less than 1% mineral naturally.

The trees from which wood is taken are normally divided into two types; hard and soft. Hardwood normally comes from deciduous (broadleaf) trees and softwood normally comes from coniferous (narrowleaf or evergreen) trees.
But there is also another type of wood used for structures called pseudo-wood, which comes from heavy-duty reeds and grasses such as bamboo and palm trees.

Physical Properties

The most useful descriptions and properties of woods may be defined below.

Moisture Content

The moisture content of wood is normally expressed as the percentage of water-weight compared to the weight of oven-dry wood. Green wood can have between 30% and over 100% moisture content, dependent upon temperature and ambient conditions.
By way of clarification, 100% moisture content means that the entrained weight of water is the same as the weight of oven-dry wood, or 62% (50%+12%) of the weight of wood with 100% moisture content is water.

Names

The common names in the woods database are in English, and the scientific names are in Latin.

Density

This property may vary by up to ±5% with age, condition and origin.

MoE

Modulus of elasticity defines the expected tensile strain (bending) for a given load in undamaged condition, which may vary by up to ±10% with the wood's age and origin.
Its plastic and metal equivalent is tensile or Young's modulus.

MoR

Modulus of rigidity represents the expected limiting tensile strain (bending) for a given load in undamaged condition, which may vary by up to ±10% with the wood's age and origin.
Its plastic and metal equivalent is maximum tensile or yield stress.

Compression Strength

This property defines the expected axial [compressed] deflection for a given load in undamaged condition, which may vary by up to ±2% with the wood's age and origin.
Its plastic and metal equivalent is maximum compressive or yield stress in the longitudinal direction.

Thermal Conductivity

This property defines the expected transmission of heat through sectional thickness in undamaged condition, which may vary by up to ±15% with the wood's age and origin, and also with surface treatment. It also affects the expected ignition temperature of the wood.

Hardness

This property defines the expected surface deflection for a given load (localised surface stiffness) in undamaged condition, which may vary by up to ±5% with the wood's age and origin.
The values provided here are based upon the Janka hardness measurement method, which is defined by the load required to impress half the diameter of a 0.444 inch (11.28mm) steel ball into the wood's surface.

Durability

The durability of wood is defined in EN 350:2016 by its ability to withstand weathering and abrasion, and is classified thus:

Class 1: Very Durable - life span of 25+ years.

Class 2: Durable - life span of 15 to 25 years.

Class 3: Moderately durable - life span of 10 to 15 years.

Class 4: Slightly durable - life span of 5 to 10 years.

Class 5: Not durable (perishable) - life span of 0 to 5 years.

Two or three coats of varnish or synthetic lacquer can decrease the durability classification (i.e. increase its durability) by one or two classes.
Sited internally with protection from fungi and insects, the life of some woods, such as oak, greenwood, ironwood, etc., can be extended almost indefinitely.

Shrinkage

The shrinkage defined in Woods describes the expected percentage dimensional change in the wood during drying from green to oven-dry condition.
Shrinkage is normally defined in two planes only; radial and tangential. Add the two values together and you will get an approximate volumetric shrinkage. Longitudinal shrinkage in all woods varies between 0.1% and 0.3%, and is usually ignored.
The direction parallel to the grain is referred to as the longitudinal direction and the two axes normal to the grain are referred to as radial and tangential with respect to the cylinder of the tree stem (Fig 1).

Plywood

Woods includes a number of plywoods, the properties of which vary with the wood veneer and resin bonding agent used in their manufacture.
The three types of bonding resin used in the plywoods included in the woods database are urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) and phenol-formaldehyde (PF).
Plywood is generally referred to as either normal or marine quality; boiling water resistant (BWR) and boiling water proof (BWP) respectively.
In reality, marine ply is simply higher quality normal plywood, neither is resistant to boiling - or any other water - unless it is suitably treated and maintained.

Fibreboard

Woods includes two fibreboards; medium-density (mdf) and high-density (hdf), both of which comprise small wood chips bound together with MUF resin.

Wood Properties Database - Technical Help

You may select any wood by its "name" and sort any numerical property from minimum to maximum from the "sort options" dropdown box.
In almost all cases, the structural properties of wood improve with age if protected from environmental attack, such as insects, fungi and moisture.

Applicability

The woods database is applicable specifically to those woods included within it, but will vary to some extent dependent upon age, thickness, origin and condition.
For example, all woods will harden and strengthen with age if they are not decayed. The properties described here are based upon relatively new, oven-dried condition.

Validity

The values quoted in Woods are believed correct by CalQlata from its own historical information. There are many sources of information for the properties some of which may vary to a greater or lesser extent.
Therefore, CalQlata would recommend that you perform those calculations you need using the material specifications in the database and then go directly to your local supplier to finalise all your material requirements and ensure specification compliance.

Further Reading

You will find further reading on this subject in reference publications^{(1, 2, 3, 12 & 17)}