Particleboard Structural Flooring Design Manual

For best viewing and printing open this file (360k), in adobe acrobat format.

Return to Contents

Particleboard flooring can provide an attractive hard wearing floor in retail areas such as this timber products store in Adelaide.

and in institutional building such as the gym at 
Tuggeranong College in Canberra

Return to Contents

3.6 Minimum Property Values

Flooring usage tables (Safe Load Tables-Section 4) are based on the minimum requirements of the Interim Australian Particleboard Standard (AS/NZS 1860 Part 1 2002).

Sheets should be pushed firmly together by hand - mechanical cramping is unnecessary

Table 1 . Allowable Concentrated Live Load - kN Max Deflection - Span/200 or 3mm whichever is greater
Table 2 . Allowable Long Term Uniformly Distributed Load - kPa Max Deflection - Span/200 or 3mm whichever is greater
Table 3. Allowable Concentrated Live Load - kN Max Deflection - Span/300 or 2mm whichever is greater
Table 4. Allowable Long Term Uniformly Distributed Load - kPa Max Deflection - Span/300 or 2mm whichever is greater

4.1 Notes relating to Safe Load Tables

4.2 Additional Requirements

The following additional requirements should be noted:

When all edges must be supported it may be more economical to use the larger square edge sheets (3600 x 1800mm) than the usual T & G sheets.

4.3 Punching Shear

If concentrated loads act on a small bearing area, there may be a risk of punching the load point through the particleboard sheet. This is termed Punching Shear.

Table 5 gives Safe Concentrated Loads assuming maximum spans for each board thickness. Support dimension is diameter for circular supports or the side for square supports.

If design involves small support sizes and loads higher than those given in Table 5, pads should be placed under the load point. A guide to pad size required can be obtained from Table 5.

4.4 Double Layers

Allowable Loads for double layers can be obtained by adding together the Allowable Loads for each individual layer from Tables 1-4 as appropriate. This is a conservative approach, but installation procedures to achieve composite action from the two layers are complex and difficult to verify and long term behaviour too is uncertain.

The additional fixing and support details of Sect 4.2 are required at Concentrated Loads higher than 6kN or Uniformly Distributed Loads higher than 20kPa. In this case the bottom sheet only requires screw fixing and full support on all edges.

Figure 2. Standard Fixing

Figure 3. Close Fixing

Particleboard Flooring is manufactured in three thicknesses - 19, 22 and 25mm and in various sheet sizes. Sheets are factory machined to produce a groove in the two long edges and a plastic tongue or spline is inserted in one side. The plastic tongue allows easier, more accurate installation and is resistant to handling and transport damage. Square edged sheets are available as specified or on request.

Particleboard Flooring is also available with fungicide and termiticide treatment. However not all companies manufacture all sizes or treated product.

AWPA Member Companies use distinctive colours of the plastic tongue to enable easier product identification. Particleboard Flooring may be factory edge sealed and again some companies use a colouring in the sealant for product identification.

The following procedure relates to the design of particleboard floor sheeting. Design of timber or metal sub-floor joists is not covered in this Manual. Joists must be designed to meet the specific load/deflection criteria.

Step 1. Loads and Performance

Determine the maximum Concentrated Loads (CL) and Uniformly Distributed Loads (UDL) to be carried by the Particleboard Flooring. Decide deflection limits to apply -usually span/300 for general traffic areas, span/200 for restricted areas or industrial floors.

Step 2. Preliminary Design

Consult the appropriate Safe Load Tables for Standard Particleboard Flooring and determine thickness/span options for the design CL and for the design UDL. There may be three CL thickness/ span solutions and three UDL thickness/span solutions.

Step 3. Refining the Design

If more than one thickness/span solution is possible, check total floor cost and select the most economic sheet thickness and joist span. If the solution indicates close joist spacing, review design CL. Does design CL apply generally over the floor, or does it represent a specific load? Would economy be served by designing special support for a specific load; does the whole floor need to be designed to carry it?

Step 4. Check Punching Shear

Consult Table 5 and determine if CL is below the safe maximum value for Punching Shear. If not, specify larger bearing areas.

Example 1
Design a hotel floor with maximum Uniformly Distributed Load (UDL) of 5kPa and Concentrated Load (CL) of 3.6kN.

Installation should be in accordance with Sect 4.2.

Example 2
An office is to be constructed in an existing building. The floor is 22mm Particleboard on joists at 450mm centres. Inspection shows that all timbers are sound, but the office floor loads are assessed at UDL = 5kPa. CL = 4.5kN.

Example 3
Single axle trolleys are being considered for use on an existing floor of 19mm particleboard on joists at 450mm centres. Trolleys carry up to 400kg load. Can the floor carry these loads?

8.1 Site Storage

Packs of Particleboard Flooring should be protected from the weather before installation. Particleboard Flooring is resistant to moisture and there is often a tendency to leave packs unprotected on building sites. Water absorption will cause expansion of the sheets and this will lead to gaps in the floor later when the particleboard sheets dry out.

As shown in Figure 4, packs should be clear of the ground with supports about 600mm apart. Covering should allow some air circulation during the storage period.

8.2 Sub - Floor

Particleboard Flooring can be installed over timber or metal joists to form a load bearing floor system. Joists must be installed such that their top surfaces are level. Timber joists must be kiln dried. Joists that are not seasoned at the time of construction may shrink unevenly as they dry out, which may lead to localised high deflection and squeaking of the finished floor. These problems can be extremely expensive to remedy some years after the project has been finished.

8.3 Sheet Layout

Particleboard Flooring sheets are laid with their long side across floor joists and ends butted over a joist. Sheet end joints should be staggered (as illustrated in Figure 5) because any slight rounding of sheet corners may present a hole in the floor if four corners come together. Select a starting point for laying and set a string line to ensure the first sheet is square with the joists. Position the first sheet with its tongued edge to the string line and note the printed information on the sheets regarding top surface.

Each sheet must be supported by at least three joists. If this is not possible (cutting in around the room perimeter) then nogging should be fixed under the edges of these smaller pieces.

8.4 Expansion Joints

Particleboard Flooring will expand and contract as sheets respond to changes in atmospheric moisture. Allowance for this movement must be made throughout the floor area by providing gaps and special joints as appropriate to accommodate sheet expansion.

A clearance of 10-15mm must be allowed along all walls and around columns or other fixtures. These gaps may later be covered by skirting.

An expansion joint is a 20mm gap in flooring sheets located above a wide (50mm minimum) or double joist. Extra joist area is necessary so that sheet ends can be properly fixed while still allowing the 20mm gap. The joint may be covered by a metal or plastic moulding, screwed into the joist, or partitioning may be located over the joint. See Figure 6.

It is difficult to provide general guidance about frequency of expansion joints. Particleboard Flooring would be supplied from the factory with a moisture content in the range of 8-11%. Long term storage in regional warehouses may raise or lower this figure but such "acclimatisation" should be of benefit in local applications.

Care must be taken to ensure that there is no likelihood of moisture build-up under the floor. Particleboard Flooring will absorb moisture (and so expand slightly) in tropical areas. Even in air-conditioned buildings, any concrete work may take a long time to dry out and cause a moist environment during this drying period. Installation procedures are based on sheets being conditioned to the building environment.

Spacing of expansion joints should be between 10 and 20m with the final decision depending upon the following assessment.

8.5 Fixing

Particleboard Flooring should be fixed with construction grade adhesive and mechanical fasteners.

A bead of adhesive is applied from the cartridge applicator to joists before positioning particleboard sheets. The bead should be 5-6mm across and must not be laid too far ahead as it may cure quickly. The time available for laying sheets before the adhesive bead becomes too hard and dry will depend on temperature and ventilation. These conditions may restrict advance adhesive application to the amount required for one sheet only.

A bead of adhesive should also be applied along the tongue before sheets are pushed together, to ensure a squeak-free floor. Sheets should be pushed firmly together by hand - mechanical cramping is unnecessary.

Solvent based adhesives should be used on steel joists due to the possibility of traces of petroleum based lubricants remaining on the steel.

8.6 Fastening

Fasteners (nails or screws) should be spaced according to the Standard Fixing or Close Fixing pattern as required in Section 4.2 (refer to Figures 2 and 3). Fasteners should not be placed closer than 25mm from tongued or grooved edges and 10mm from the short, butt jointed ends.

Nails may be driven by hand or by nailing gun. With gun nailing, care should be taken to adjust the air pressure for softwood or hardwood joists, so that nails do not penetrate the surface by more than 1mm.

Table 7. Fasteners for Particleboard Flooring

Nails may be Bullet, Jolt, Flat or Countersunk heads for hand driving or Tee or Finishing head for power driving. Countersunk, self-drilling screws should be used for timber joists, while steel joists require countersunk, self-drilling screws with self breaking cutter nibs. Twist shank hardened nails should be used for power driving into steel joists.

Number of Fasteners per Sheet 

450mm joist spacing - 42 Standard Fixing

                               - 62 Close Fixing

600mm joist spacing - 34 Standard Fixing

                               - 50 Close Fixing

8.7 Double Layers

Install the first layer as specified in this Section. The second layer should be laid so that the long joins are staggered between the two layers and end joins meet on a different floor joist (see Figure 7). Run a bead of adhesive on the first layer at joist positions and fasten through both layers into floor joists. Fastener length for the second layer should provide at least 30mm penetration into joists.

Figure 7.  Double Layer Layout

Wood Panel Products

Normal health and safety precautions should be taken when working with wood panel products. Machine tools should be fitted with dust extractors and work areas kept clean.  If dust levels exceed the National Occupational Health and Safety Commission (NOHSC) standards, the wearing of a dust mask (AS1715 and AS1716) and safety glasses (AS1337) is recommended.

Storage and work areas should be adequately ventilated.  If large quantities of Particleboard and Medium Density Fibreboard are stored in non-ventilated areas, formaldehyde emissions could accumulate to levels which may irritate some people.

For further information, please contact one of the manufacturers listed below for a copy of a Material Safety Data Sheet or download from www.woodpanels.org.au .