Panel products

Applications

Flooring and sheathing

Panel materials are most often used as flooring (typically particle board) or sheathing (particle board or MDF) to carry face loads that are applied perpendicular to the surface.

Design of flooring is a combination of calculation and prototype testing with point loads on defined small surface areas where the behaviour is difficult to calculate accurately. 

Refer to the manufacturers’ literature for span tables and design information.

Bracing

For domestic dwellings, sheet materials fixed according to the requirements of NZS 3604 provide excellent wind and earthquake bracing.

The sheet materials used should have durability in excess of code requirements for structural use, and designers should consider what happens if windows fail in cyclone or high wind conditions, and the sheet material gets wet.

Some panel adhesives or binders have limited durability in wet conditions.

Care must be taken to ensure that reactions in the bracing panels are distributed to the foundations with nailed steel strap or other suitable fixings.

With inadequate holding-down details, the panel is free to overturn and provides little resistance to lateral loads.

Shear walls are larger versions of wall bracing where special attention must be given to jointing and splicing of critical members, and holding down to the foundations.

Diaphragms

Many floors or ceilings are required to behave as horizontal diaphragms, to assist in transferring lateral loads to vertical bracing.

To create a structural diaphragm from a floor or ceiling, the cost of more detailed jointing is often the only additional cost since the sheet material is already required for the flooring, sarking, decking or sheathing, and the lateral load resistance is achieved by detailing to distribute the loads.

Likewise sheet ceiling bracing must be correctly fixed to the wall bracing panels if it is required to distribute loads.

Wall and ceiling panels

Triboard is used for wall and ceiling panels, typically in pre-fabricated housing applications. 

Tempered hardboard and fibre cement are used as a substrate for wet area panel sheathings.

Flameguard is a low density softboard insulating product with fire retardant.

Triple S is softboard with bitumen emulsion for sub sheathing, replacing less rigid roofing papers or building papers under plaster or brick veneer. 

Perforated hardboard panel (pegboard) with 4.8mm diameter holes in staggered rows, is used as ceiling or wall panels.

Engineered  I-Joists

OSB is a common web material in I-joist manufacture.

Formwork

Tempered hardboard can be used for formwork. 

Particleboards are not generally suited except when they are used in sacrificial applications (e.g in foundations) where the additional deflection of a wet board is acceptable.

Furniture and Joinery

MDF is used extensively in furniture and joinery, because it has higher strength than conventional particleboards and it can be given a superior edge.

Manufacture

Particleboards, wafer boards, strandboards and fibreboards are composed of particles of various sizes or fibres obtained from refinement of wood chips.

There are basically two ways of making these materials. Particleboard and MDF (medium density fibreboard) are made in a “dry” process with added adhesives, whereas hardboard and softboard type fibreboards use water as a processing medium in a “wet” process to form hydrogen bonding (softboard) or lignin bonding (hot process hardboard).

Adhesives are sometimes used to enhance the quality of wet process boards.

Final board properties are influenced by particle size and orientation, binder type, additives such as wax or emulsifiers, distribution of particles in the board, layering, final density, and a range of pressing variables.

All these may vary between product and manufacturer, and are usually optimised for a given resource of a species or raw material, be it sawmill waste or purpose made chips or flakes from logs.

Most New Zealand boards are made from radiata pine but may contain proportions of willow, poplar, beech or other species to achieve desired properties or economies.

These boards have a tendency to swell more than solid wood on exposure to moist environments. This can be reduced by use of high quality adhesives and additives such as wax.

Developments in board and particle composite products include incorporating particle alignment to improve strength, addition of fire retardants and stabilisers, and the development of linear lumber composites such as laminated strand lumber and Parallam.

Download the PDF below for further information on the manufacture of the following:

• Particle type boards.

• Medium Density Fibreboard.

• Triboard.

• Hardboard and Softboard.

• Laminated Strand Lumber.

• Parallel Strand Lumber.

• Oriented Strand Board.

• Cement Fibreboard.

Manufacture of Panel Products - Printable PDF

Availability

Most panel products are manufactured in 1.2 m x 2.4 m size, with some flooring particle boards 1.8 m x 3.6 m.

Some products are still made to the old imperial measure of 1.22 m x 2.44 m (4 feet x 8 feet). Consult manufacturers’ literature to check available sizes.

Some will manufacture non-standard sizes.

Suppliers Database

Performance

General

Some panel products have excellent shear properties in the plane of the sheet. When nailed to a timber frame, they provide excellent racking resistance.

By careful design of the sheeting, the fixing (nails and/or gluing) and the framing members, these properties can be exploited with great economy in both small and very large components. 

For structural design with panels, special study should be made to determine board and fastener properties as well as adhesive durability for structural performance and control of creep deformation. 

Particleboards and fibre boards are highly prone to creep.

Test data derived for board quality control using appropriate standards for particle boards or fibreboards as appropriate is given in manufacturers’ literature.

Particleboard and fibreboard composites tend to have low stiffness for their strength and so deflection often governs designs in bending.

Before characteristic stresses can be published, more must be known about the load duration, creep and large panel strength of the materials.

Data needs to be evaluated for each panel product to obtain characteristic stresses and fastener loads.

Designers should ensure that the panels chosen for each application have an adhesive bond that meets structural durability requirements for the given environment. 

Phenolic glue is a proven structural exterior adhesive (weather and boil proof) whereas glues like PVA are non durable in humidity cycles, and non-structural. 

Some urea based glues have limited durability, others are melamine fortified and have better performance.

Particle and fibre boards have much lower fibre strength (e.g MoR) and stiffness (e.g. MoE) than solid wood or plywood, so need to be much thicker for the same spans and loadings, but they can be cheaper.

Flooring design

For specific design of flooring for other than NZS 3604 applications refer to the manufacturers literature:

The Laminex Group website

Kopine website

Durability

Movement of panel products

Linear expansion and contraction that occurs in panel products with changes in moisture content is generally smaller than in solid wood because of the influence of adhesives and manufacturing processes. Table 1 gives typical values.

Moisture content and movement properties of some panel products.