Timber comes in many varieties. Even the same timber species can have different varieties, so the wood grading system is used to classify different timber types based on qualities like appearance, strength, usability, etc.
It is a good idea to know how timber grading works to ensure you can select the best timber for your project.
What is Timber Grading and Why is It Important?
Timber grading is the process of assigning grades to wood based on their distinct characteristics. In other words, it involves dividing timber into groups of similar characteristics.
Timber grading makes it possible to choose the right timber for a project based on what you desire or want in your wood material. It allows wood buyers to define what they want in their timber and enables sellers to produce the material that their buyers want.
What Criteria Are Considered in the Timber Grading Process?
The major things to be considered when grading timber include the wood’s utility and its physical properties.
The utility of wood, i.e. how fit the timber is for a particular purpose or for what purposes it is fit to use.
The visual characteristics of timber, include how the wood looks and its physical properties, such as stability, workability, strength, durability, moisture content, and appearance.
Timber ‘Grade Definitions’ define the various parameters used to grade wood.
Types of Timber Grading Methods
If you’re wondering how timber is graded, here are the common types of timber grading methods popular today.
- Visual Grading: In this type of timber grading system, the wood is assigned a grade based on how it looks. A trained assessor visually impacts a piece of timber and assigns a grade based on their understanding of the different elements that might affect wood’s appearance, such as the presence of knots, defects, etc. This wood grading method is particularly suitable for wood that is intended to be used for its appearance, such as interior construction.
- Machine Grading: This type of wood grading system involves the use of machines. Testing machines or sensors are used to compare wood’s characteristics against predefined grading criteria and appropriate grades are assigned accordingly. This is a more accurate and faster method of wood grading, however, it is less commonly used due to its high cost.
- Proof Grading: This grading system is used to re-evaluate and re-grade wood that has already been graded under either of the first two methods. This method is particularly used for construction or structural wood to ensure the wood can take the loads as defined in its grade. The method involves applying the said loads to check the wood’s strength & stiffness.
Grading is usually done after the timber has been dried and surfaced.
Softwood vs Hardwood Grades
Different grades are used for different types of wood, including softwood and hardwood.
Softwoods are woods sourced from coniferous trees, i.e. trees that are evergreen and shaped in the form of a cone. Softwoods are generally less hard and durable than hardwoods.
Hardwoods are procured from deciduous trees, i.e. trees that lose their leaves once a year. These woods are harder and stronger. Hardwoods are generally more expensive than softwoods because of their slow growth rate and limited availability.
Softwood Grading Methods
Softwoods are generally assigned grading based on their usability. Most of the softwood is used for construction purposes and can be divided into appearance timber, stress-graded, and non stress-graded.
Appearance-graded timber is intended for use primarily for its visual aesthetics, while the other two types of softwood timber are judged based on their structural characteristics, such as strength, stability, and durability.
Non-Stress Grading (Common grading)
Pieces that are graded with non stress-grading are judged based on both their appearance and usability (structural). In other words, these pieces are both beautiful and strong.
There are 5 grades of non stress-graded timber:
Grade 1 – Construction timber – contains some tight knots. Good appearance. Paints well. Suitable for shelves, panelling, and siding.
Grade 2 – Standard timber – contains too many large and notable knots. Easy to paint. Used for panelling, cabinets, and siding.
Grade 3 – Utility timber – contains knotholes, cracks, and splits. Difficult to paint. Used for subflooring, sheathing, crates, etc.
Grade 4 – Economy-grade – contains large holes and defects. Doesn’t paint well. Suitable for subflooring, sheathing, etc.
Grade 5 – Economy wood – Most part of the timber is waste wood. Not very usable.
In this type of softwood grading system, the wood is judged primarily based on its physical appearance. This is particularly done for timber intended to be used in applications where it will be exposed, such as softwood furniture. The three major grades in this timber grading system are – finish, select, and common, with the finish being the highest grade wood.
Grade A – Finish – Perfect, smooth lumber with no visible knots, splits, or defects.
Grade B – Select – wood with a few, very small defects or knots.
Grade C – Select – Small but visible knots. One side may be free of defects.
Grade D – Select – Contains pin knots and other minor defects.
Grade 1 – Common – Contains many small, tight knots that might give it a knotty appearance.
Grade 2 – Common – Contains large, tight knots.
This timber grading mechanism is used for wood intended for use in structural applications such as beams, rafters, posts, studs, and joists. In other words, wood that is used in a load-bearing capacity is graded as structural lumber.
Structural Light Framing – suitable for applications where high-strength values are desired.
- Select Structural
- No. 1 & BTR
- No. 1
- No. 2
- No. 3
Light Framing – used for general framing applications such as blocking, wall frames, sills, plates, and cripples.
Stud – For lumber intended for vertical use such as a load-bearing timber wall.
Structural Joists & Planks – large lumber designated for use in flooring, rafters, trusses, joists, and headers.
- Select Structural
- No. 1 & BTR
- No. 1
- No. 2
- No. 3
Hardwood Grading Methods
Hardwoods are generally easier to grade than softwoods.
The factors to consider when grading hardwoods are kind of the same, including the wood’s appearance and physical properties.
In the case of hardwoods, the appearance of the wood is an important factor when grading the timber. Other than the appearance, the size and number of pieces are other crucial factors considered for grading. Trees that can provide large pieces of clear, defect-free wood are graded higher. In other words, high-grade woods will have a major portion of usable material, as opposed to lower-grade woods with lower usable material yield.
High-grade hardwoods can be divided into the following three types:
- FAS (Firsts and Seconds) – the highest grade hardwood with both faces of the board meeting FAS grade requirements.
- FAS/1F (FAS-One-Face) – one face of the board is required to meet the FAS requirement, while the other can have a number 1 common grade.
- Sel (Selects) – same requirements as FAS but reduced length and width.
The higher-grade hardwoods are considered suitable for a range of premium and common timber applications, such as furniture, cabinetry, flooring, outdoor applications, mouldings, etc.
Then, there are common-grade hardwoods, i.e. woods that are not as aesthetically appealing as high-grade woods and also have lower physical qualities, moderate strength and durability, etc. These are divided into two grades – No. 1 Common & No. 2 Common.
- Number 1 Common (No. 1C) – Also called cabinet grade wood, this is particularly used for making kitchen cabinets and furniture.
- Number 2A Common (No. 2AC) – also called economy grade, this wood is suitable for hardwood flooring and is also used for building small furniture parts.
Common grades are considered suitable for common applications, including furniture parts, cabinetwork for kitchens, plank, plywood, strip flooring, etc.
What is the Best Timber Grade for Interior Applications?
Woods that are beautiful-looking and have good to moderate strength are favoured for interior applications. Parts of furniture, cabinets, etc. that remain hidden from the plain eye will not even have to look beautiful.
Softwoods are usually a great option for interior woodwork because they are an affordable, strong and durable option and also look good. However, for premium projects, such as high-end furniture, cabinets, musical instruments, and flooring, hardwoods can also be used.
Make sure to always check the grade of wood before purchasing. If you’re not sure which grade of wood is right for you, consult with an expert or ask your local timber wood supplier.
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