Barecore

[edit] Introduction

Barecore is a wood-based panel made by joining pieces of solid timber side by side to form an unfinished core. It is principally used as a component in the manufacture of faced wood-based panels, including blockboard, and can subsequently be covered with timber veneer or other sheet materials.

The individual timber strips are bonded along their edges to form a continuous panel. Depending on the construction and intended application, the resulting core can provide a relatively lightweight and machinable alternative to a core made entirely from a single piece of timber.

The terminology used for these products varies between markets. Barecore is sometimes described as a solid wood core panel or lumber-core panel. Lumber is the North American term corresponding broadly to timber in UK usage. Blockboard, however, generally refers to the completed faced panel rather than the unfinished barecore itself.

[edit] Construction and manufacture

Barecore is manufactured from relatively small pieces of solid timber, which are cut to the required dimensions, dried to an appropriate moisture content and assembled edge to edge. The pieces are bonded to form a panel, normally with their grain running predominantly in the same direction.

The construction differs from plywood, which is made from layers of wood veneer with adjacent layers generally arranged with their grain directions at right angles. Barecore therefore retains characteristics associated with solid timber, while the assembly of multiple pieces allows smaller sections of timber to be used to manufacture larger panels.

The adhesive system is an important part of the specification. Different adhesive systems can provide different levels of bond durability and resistance to moisture. The appropriate adhesive depends on the intended application and service environment. Formaldehyde emissions may also need to be controlled where the finished panel is used in applications subject to relevant emissions requirements.

Barecore is normally supplied as an unfinished core. It can subsequently be faced with veneer, plywood, fibreboard or other sheet materials to produce a finished panel. In blockboard, for example, a core of parallel timber strips is generally enclosed between facing layers.

[edit] Timber species and properties

A range of timber species can be used for barecore. Lightweight species are particularly suitable where low panel weight and ease of machining are required. Albasia, falcata or sengon are common trade names associated with Falcataria species used in timber production in South-East Asia. The botanical classification of this timber has changed over time, and names including Falcataria moluccana, Albizia falcataria and Paraserianthes falcataria are encountered in technical and commercial literature. The currently accepted name in Kew's Plants of the World Online is Falcataria falcata.

Other softwood and hardwood species may also be used. Examples specified for barecore products can include jabon, meranti, balsa, merbau and pine. The suitability of a particular species depends on factors including density, strength, dimensional movement, workability, availability and compatibility with the selected adhesive.

The physical properties of barecore vary considerably according to the timber species, density, moisture content, strip dimensions, bonding method and quality of manufacture. Consequently, a nominal density or strength value should not be assumed for barecore as a generic material.

Barecore should also be distinguished from a finished structural panel. It should not automatically be assumed to be suitable for structural applications merely because it is manufactured from solid timber. Where it forms part of a load-bearing component, the properties of the complete panel and its construction should be assessed against the relevant performance requirements.

[edit] Applications

The principal application of barecore is as the core of composite wood-based panels. After manufacture, the core can be faced with veneer or other sheet materials to provide a finished surface and improve the dimensional stability and appearance of the panel.

Applications can include:

• Blockboard and related core-board products.
• Door leaves and door components.
• Furniture components and carcasses.
• Shelving and joinery components.
• Interior panelling and fittings.
• Other manufactured wood products requiring a solid-timber core.

Blockboard is a closely related but distinct product. It generally consists of a core of parallel bonded timber strips faced on both sides with veneer or another sheet material. Designing Buildings describes conventional blockboard cores as consisting of parallel rectangular timber strips, with the finished panel commonly used for applications including doors, shelves, tables, panelling and partitions.

Laminboard is another related construction in which the timber strips forming the core are generally narrower than those used in blockboard. Designing Buildings distinguishes laminboard from blockboard principally by the dimensions of the strips forming the core.

[edit] Specification

Barecore is not defined by a single universal panel size, thickness or density. Specifications vary according to the manufacturer, timber species, intended application and subsequent processing.

The following table retains the dimensional and material information associated with the product specification from which this article was developed. These values should be regarded as example product specifications rather than general standards applying to all barecore products.

Other relevant specification requirements can include timber grade, strip dimensions, dimensional tolerances, surface quality, adhesive type, bond durability, formaldehyde emissions classification and intended service environment.

Moisture content is particularly important because timber changes dimension as its moisture content changes. A panel manufactured at a moisture content appropriate to its intended environment is less likely to undergo excessive movement after installation. The appropriate moisture content nevertheless depends on the intended service conditions and should not be inferred solely from a nominal product range.

Where barecore is subsequently faced to produce blockboard or another composite panel, the specification of the complete panel should also consider the thickness and properties of the facing materials, adhesive system, balance of the construction and intended use.

[edit] Related articles on Designing Buildings

• Blockboard
• Battenboard
• Laminboard
• Engineered wood products
• Engineered timber
• Plywood
• Veneer
• Furniture
• Physical properties of wood
• Timber core board