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Types of Carcassing Timber

Carcassing timber is a term used to refer to timber processed for use in structural applications including floor joists, roof battens, roof trusses, cladding, decking supports and studwork for partitioned walls.

What is Carcassing Timber? 

Structural timber comes in a wide range of strengths, sizes, and lengths and can be treated with a preservative or left untreated depending on the project.

carcassing timberHere are the different types of carcassing timber:

  1. Treated regularised kiln dried C16

This type of timber is used for structural applications including timber framing, floor/ceiling joists, and roof rafters. It is also ideal for use in general construction where load-bearing is required.


  • Is regularised for dimensional consistency and to ease handling.
  • Strength graded to C16 for structural performance.
  • Is kiln dried for a better-machined finish and greater stability.
  • Pressure treated to prevent rot and decay.
  1. Sawn kiln dried C16

This timber is used in load bearing projects and internal building work including mid-level flooring joists and partitioning.


  • Is graded to C16 strength for structural use.
  • Planed to regular widths for accuracy.
  • Slow grown for higher strength and durability.
  1. Treated sawn

Treated sawn timber can be applied in different construction projects including stud partition for walls, floor/roof joists, and general joinery. The timber can also be used in applications where extra protection and lifespan is required. These applications include outdoor or garden projects such as repairing a shed and trellis work.


  • Treated to protect against fungal attack.
  1. Sawn kiln dried

Sawn kiln dried timber can be used in internal construction projects such as framework and boxing in pipes.


  • Is slow grown for better strength and durability.
  • kiln dried for greater stability.
  1. Treated studwork

This timber works well in general structural applications including stud wall partitioning.


  • Pressure-treated to protect against fungal and insect attack.
  • Is regularised for dimensional consistency.
  • Is graded to C16 for use in applications where support and load bearing is required.
  1. Studwork

Studwork timber is ideal for use in wall partitioning, particularly in high moisture areas such as basements.


  • Is rounded on four edges for easy handling.
  • Is graded to C16 for applications where support and load bearing is required.
  1. Roof battens

Roofing battens provide a good fixing point for roofing sheet and tiles.


  • Is pressure treated to protect against decay.
  • Pre-graded to comply with BS5534.

The Application of Carcassing Timber and the Options Available

Carcassing timber is also referred to as structural timber because it is machined purposely for structural applications such as floor/ceiling joists, roof trusses and decking support. It is often referred to as the first set wood and may be visible but sometimes not with it being an integral part of any building structure.

Carcassing timberStructural wood has many applications, which involve using it as background material. It is an integral part of any construction project, and the timber may be seen or not, depending on the plan. In most cases, the timber covers a substrate or is over clad, which is why it is not suitable for painting or other direct decoration. Spruce and pine are two of the softwoods used to create this type of timber. The engineering of the timber pieces depends on the specific applications. Structural timber comes in various forms to suit the different elements of construction.

Carcassing Treatment

Structural timber can be treated or not. The treated of timber applies extreme pressure to inject preservatives. Therefore, pressure-treated carcassing will last longer than the untreated variety because it has protection against rot and fungal decay. The strength of treated timber is another reason it has become a more popular choice than untreated wood. Due to its resistance to pest damage and moisture penetration, pressure-treated wood has low maintenance demands.

The pressure treatment of carcassing may vary from one manufacturer to another. Typically, customers get treated structural wood, depending on its uses. For example, timber that is used above ground and may be exposed to wetting such as decking supports is treated differently than wood that will stay permanently dry.

Timber Grading

Carcassing timber can also vary on whether it is graded or not. Graded timber is suitable for load-bearing applications. The grading process divides timber into several classes, depending on their strengths. In the UK, customers can choose between C16, C24 and TR26 with the last two ranking higher in structure grade than C16. Graded timber is achieved by drying it in a kiln, which means that the excess moisture is removed. British carcassing is only able to achieve a C16 strength class because this type of wood grows in a warmer climate, which results in a faster growth rate than other kinds of structural wood. Machine grading requires the timber to undergo specific tests, including deflection under applied pressure. After the grading process, a manufacturer stamps the wood piece to indicate the producer, grade, condition and ID number. This stamp is what customers use to tell the timber quality.

carcassing timberDimensional accuracy, proper classification and preservation are important considerations when selecting the ideal wood for the project. Each asset has several variables that can have a significant impact on the value of wood. Sometimes its value suffices to justify the harvest, sometimes not. From the point of view of size, type and environmental concerns, at Theo’s Timber, we think they are things to consider. Let’s inspect each one.

The Size of tree or timber

The diameter and the length of the trees vary. We relate these changes to species and age. Diameter at Breast Height is a standard measure of trunk width. Depending on the end use of the wood the sawmill may require a minimum diameter of 8 inches, which is the minimum size required to cut most types of construction panels. The sawmill must therefore have a minimum width of 4 inches.

If you are looking for a tree with many branches, you may not have enough value to carcassing timber. We can use the wood up for paper pulp, which is usually the least important end use. Big trees are better.

Species of the tree

Forest species have a significant impact on the value of the carcasssed wood. If the tree is different, the wood is different. If the wood is different, the end use will be different the market value varies depending on the application. For simplicity, the simplest way is to divide the tree type into two basic categories: hardwood and softwood/conifer.

  • Hardwoods

In most cases, hardwoods are harder than conifers. This may not always be the case, but it is. As a result, hardwoods are more durable than conifers. It applies to certain applications where conifer is not suitable. Hardwood has many important uses. We use this wood in the manufacture of fuels, tools, furniture, barrels, musical instruments and many more.

  • Softwoods

They account for about 80% of the world’s timber production. Most conifers have needles or no broad leaves. Conifers grow much faster than hardwood. People commonly use them for structures, floors, woodwork, beams, strips, pulp, etc. they include;

Eucalyptus, pine, Himalayan cedar, cypress, spruce and kauri.

When buying carcassing timber, be clear about the exact type of wood required for the application; is it treated or untreated, graded or ungraded.

Environmental Concerns on Carcassing Timber

For those who raise concerns about the impact of harvesting on the environment, please note that cutting trees can also affect the environment. However, it is important to note that over the last century, the timber harvesting strategy has become more environmentally friendly. In areas where we still need continuous forests, the current harvesting method is to leave many small trees and let them grow on shorter time.

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