Timber Treatment

TIMBER TREATMENT & GRADING SERVICES

Wood and wood-based products can be processed or refined in various ways to change some of their attributes. There are various ways by which we can influence or affect important properties of wood, including timber durability, dimension stability, hardness, and moisture absorption. Some of these popular ways or timber treatment methods to change timber properties include:

• Fire protection timber treatment
• Dimensional stabilization
• Timber treatment against fungal and insect attack
• Hardening

Timber Prevention Approach

Timber protection or prevention generally refers to the process of protecting wood or wood-based items from harmful attacks made by wood-decaying fungi, insects, mould, blue stain and marine pests like shipworm.

While preparing wood-based material, the structuring should be done in such a manner that it supports the wood protection practices exercised against wood-decaying insects or fungi. This is also known as structural protection of wood against harmful fungal or insect attack.

The primary goal behind such practice is to limit the amount of moisture content in wood for a longer time period. Temporary damp should also be made so that moisture quickly dries out from timber and returns to its normal level.

Wood with better durability can also be considered in scenarios where structural timber protection and high moisture elimination is not possible.

There are certain kinds of woods and tree trunks that offer much better durability. Some timber treatment tricks can also be applied to modify the wood for increasing its durability value. Adding chemicals in wood is also one way to level up the durability.

Timber Treatment Grading Services

There are two popular methods, which are used globally for grading of sawn timber:

1. Grading per piece of wood on the basis of the number of “standard” defects with respect to its size.
2. Timber Grading on the basis of clear surfaces in the wood. In other words, the grader determines the total percentage of undefeated square surfaces in relation to the whole surface of the wood piece. Following such a method, the grader is able to calculate the total percentage of defect-free surface, which also helps in determining the grade of the piece. This method is popularly followed across many grading associations, including the National Hardwood Lumber Association Rules (NHLA), Malaysian Grading rules (MGR), and the SATA Rules Sciages Avivés Tropicaux Africains: Traditional African Sawn Timber. This also creates confusion among people purchasing wood as different quality lumber carries the same name.

Such confusion has started from Britain, a dominant trading country of hardwood and softwood. Wood traders from the UK for long have used an oral “system” for grading of wood until certain producers have transformed into written form, but it never became a uniform rule.

In order to avoid all disputes and interpretation differences arising due to the (original, oral) timber grading system, ATIBT’s Commission III has decided to form clear rules for wood grading.

General Timber Treatment Grading Rules

1. Timber should always be well-sawn while having dimensions above the contractual ones so that it can be shrunk to dry easily and also meet the expected moisture content level of 20% as per the contractual dimensions.

• Each parcel in totality should be a sum of individual species and grades.
• Apart from being stipulated, each piece must be graded on its worst face.
• Percentages should always be calculated based on the volume unless specified otherwise.
• According to the parcels, the quantity should always be within the limit of ± 10% of the total volume with a max fluctuation of 20 m3 (or 700 cubic feet). Although for fixed dimensions the quality should stay within the limit of ± 5% of the volume and a max variation of 10 m3 (or 350 cubic feet).

For Standard Timber Grades

1. First and Second Grade – (FAS)

The FAS wood grade should not have defects and sapwood more than 60% whereas not less than 40%. The clear sapwood should not exceed 10% of the total width of a particular piece. The grade should be of good texture whereas 3% of the volume of interlocked grain is expected as tolerance.

• Total defects can be 1 In a piece under 1.00 m² (less than 10 square feet)
• Total defects can be 2 In a piece 1.00 m² to 1.50 m² (10 to 16 square feet)
• Total defects can be 1  3 in a piece over 1.50 m² (over 16 square feet)

2. Number 1 Common and select Grade

Clear sapwood should not exceed 20% of the width. Some variation in texture and grain is allowed in grade:

• Total defects can not be more than 1 in a piece under 0.60 m² (less than 6 square feet)
•  Overall defects can be 2 in a piece 0.60 m² to 1.00 m² (6 to 10 square feet)
• Total defects can be 3 in a piece 1.00 m² to 1.50 m² (10 to 15 square feet)
• Total defects can be 4 in a piece over 1.50 m² (over 16 square feet)

3. Number 2 Common Grade

No restriction on the amount of clear sapwood. Light to medium blue stains, dead pinholes (isolated and/or in clusters, not more than half of the surface plus a max of 10% of the piece in the single parcel) are allowed in the piece. Abnormal grains are also allowed considering it does not deteriorate the flatness and strength of the piece. Colour and density variation is also allowed.

• Total defects are limited to 1 in a piece under 0.60 m² (less than 6 square feet)
• Total defects are limited to 2  in a piece 0.60 m² to 1.00 m² (6 to 10 square feet)
• Total defects are limited to 3 in a piece 1.00 m² to 1.50 m² (10 to 15 square feet)
• Total defects are limited to 3 in a piece over 1.50 m² (over 16 square feet)

SPECIAL TIMBER TREATMENT GRADES

1. Prime Grade must be defect-free with sapwood ranging at least 80% whereas up to 20% with defects below the set limits.

2. Prime Narrows Grade: straight and defects fee grades are permitted only.

3. First and Second (FAS) Shorts Grade: In specs of 15 cm (6 in.), pieces de 20 cm (8 in.), or wider are permitted with one defect. In specs of 7.5 cm(3 inc.), pieces de 15 cm (6 in.) or wider are permitted with one defect.

4. Prime Strips Grade:  Better face should be defect-free. The reverse side and 1/3 of the thickness of its adjacent edges can only have one defect for each 1.20 m (4 ft) of length.

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