Kiln-Dried vs Unseasoned Timber: What's the Difference?

Timber is supplied in a variety of forms depending on how it will be used, with moisture content being an important consideration when selecting the right product.

Two terms that are commonly encountered are kiln-dried and unseasoned timber. While both have their place across the timber industry, the difference between them can influence how timber performs, moves and should be used.

Understanding the distinction can help architects, contractors, manufacturers and merchants make more informed decisions when specifying timber for different applications.

Unseasoned timber, sometimes referred to as green timber, is timber that has not been deliberately dried to reduce its moisture content after conversion.

Because it retains a higher level of moisture, its weight and dimensions can change as it dries. Timber naturally responds to changes in its surrounding environment, with moisture loss or uptake causing it to shrink or swell.

This doesn't make unseasoned timber unsuitable. In fact, it remains widely used across a range of applications where its characteristics are appropriate.

Taylor Maxwell supplies unseasoned timber for a variety of purposes, including fencing, landscaping, pallet and packaging applications and general construction products. Its general construction timber range, for example, includes both unseasoned and kiln-dried boards for uses such as gravel boards, path edging, sarking and bracing.

The important consideration is whether the timber's moisture content and expected movement are appropriate for its intended application.

Kiln drying is a controlled process used to reduce the moisture content of timber.

Rather than relying solely on natural drying, timber is placed in a controlled environment where temperature, humidity and air movement can be managed. This allows the moisture content to be reduced to a level appropriate for its intended end use.

Moisture content has an important influence on timber's properties, including its weight, workability and dimensional stability. The Timber Research and Development Association (TRADA) identifies moisture content as one of the most important factors affecting the performance of wood.

Kiln drying can therefore provide greater control over the moisture content of timber before it reaches the point of use.

Taylor Maxwell supplies a range of kiln-dried products, including C16, C24, CLS and TR26 construction timber, as well as kiln-dried hardwoods such as European Oak, American White Oak, Sapele and Tulipwood.

Timber is a natural material, so it doesn't remain completely dimensionally static.

As timber gains or loses moisture, it can expand or contract. The extent of this movement varies depending on factors including the species, grain direction and the difference between the timber's moisture content and the conditions in its intended environment.

This is particularly important when timber is being incorporated into applications where dimensional stability is important.

Moisture content as a key consideration in timber specification. Drying, shrinkage, movement, and the measurement of moisture content all need to be considered when selecting and using timber.

For example, timber intended for an internal environment may need to reach a moisture content closer to the conditions it will experience in service. Simply specifying timber as "kiln dried" is not necessarily enough; the required moisture content should be considered in relation to its end use.

There isn't a single answer. The choice between kiln-dried and unseasoned timber depends on the application, required moisture content, expected environmental conditions and the characteristics required from the finished product.

For some external applications, unseasoned timber is an established and appropriate choice. Taylor Maxwell's fencing range, for example, includes both unseasoned and kiln-dried redwood and whitewood, with treatment options available in Use Classes 3 and 4.

For applications where greater control over moisture content and dimensional movement is required, kiln-dried timber may be more appropriate.

The same principle applies across manufacturing. Taylor Maxwell supplies timber to the pallet and packaging sector as unseasoned, heat treated or kiln dried, depending on customer requirements and application.

Therefore, it is not simply choosing between "dry" and "wet" timber, but understanding what the timber’s purpose is once it reaches its final environment.

Selecting the right timber involves more than choosing a species, size or grade. Moisture content, drying method and the conditions in which the timber will be used can all influence how the material performs. Considering these factors at the specification stage can help minimise unwanted movement and ensure the timber is suitable for its intended application.

For architects, contractors, manufacturers and merchants, understanding the difference between kiln-dried and unseasoned timber provides another useful consideration when selecting materials.

Taylor Maxwell supplies a broad range of timber products through established UK and European sawmill partnerships, covering construction, fencing and landscaping, pallet and packaging, hardwoods and flooring. With over 60 years' experience in the timber industry, the team can support customers in identifying products to meet their specific requirements.

Whether timber is kiln dried or unseasoned, the right choice starts with understanding how and where it will be used.

Speak to the Taylor Maxwell Timber team to discuss your timber requirements and find the right solution for your application. Get in touch here.