information/FAQs

Fig 1(a) No vapour barrier

Fig 1(b) Alternative to 1(a)

Fig 1(c) Vapour barrier

Plywood flooring over battens on concrete

One way of installing a floor over concrete is to fix battens to the concrete, then attach plywood flooring over the battens. This system requires greater floor to ceiling height than attaching the plywood directly to the concrete. The batten solution is particularly attractive for the following reasons:

It provides alternatives as to the way in which the moisture content of the slab can be controlled
Allows the floor to retain at least some of the resilience for which timber floors are noted
Allows relatively easy levelling of the floor surface through sizing of the battens
Allows ventilation of the floor if required
It provides a cost-effective solution.

NOTE: Minimum structural plywood flooring thickness versus stress grade and batten spacing must be as recommended in AS1684 - Timber Framing Code and the information contained in the article "Plywood: Installation of residential flooring".

Three cases involving the use of battens are considered. Figures 1 (a), (b) and (c) show plywood/batten/slab arrangements with the vapour barrier in various locations.

Case 1(a)

The preferred construction procedure to be followed if a vapour barrier has not been provided under the slab is shown in Figure 1 (a). Table 1 gives the fixing requirements for attachment of the plywood sheathing to the battens.

Case 1(b)

An alternative method available if a vapour barrier has not been provided under the slab is shown in Figure 1(b): Fixing of the plywood to the battens should be done by nailing only as specified in Table 1.

Case 1(c)

The third option, where the vapour barrier is provided under the slab, is illustrated in Figure 1(c). Table 1 gives the fixing requirements for attachment of the plywood sheathing to the battens.

NOTE: The glued option is the most difficult to implement because of the need to apply uniform downward pressure.

Finishing

Sanding should produce the desired surface finish. For a high quality finish it is recommended that a professional sander be used. It must be remembered that a veneer is being sanded not a solid piece of timber. To protect the quality of the wood surface from deterioration due to weathering or construction dirt, it is recommended that a 20% strength coating of the final finish be applied to the surface as soon as possible after laying. This is particularly important in new buildings in which the flooring is exposed to finishing trades. This protective coating is sanded off prior to the final finishing coat leaving a high quality surface ready for finishing.

Reference: Plywood Association of Australia brochure "Timber tops for concrete slabs"

TABLE 1: INTERCONNECTION REQUIREMENTS - PLYWOOD TO BATTENS

PLYWOOD SPECIFICATIONS				NAILING SPECIFICATION		GLUING SPECIFICATION
Stress grade	Thickness minimum (mm)	Batten Spacing(mm)	Connection type	Type	Centres(mm)	Type	Bead Width (mm)
F11	13	450	nailed only	Deformed shank or bullet head, 2.8mm dia. ´ 50mm long	150 along ends 300 on intermediate battens
F14	12.5 NOTE: normal to use 15mm			NOTE: Where pine battens are used, deformed shank nails are recommended
as above	as above	450	glued only NOTE: Vertically downward pressure must be applied to the plywood surface during curing to ensure a good glue bond			must meet or exceed American Plywood Association requirements for AFG-O testing	10mm
as above	as above	450	glue/nailed	as for nailed only	300	as above	10mm
					450 centres
F11	18.5	600	nailed only	as for nailed only	150 ends 300 intermediate
F14	17	450 centres
as above	as above	600	glued only (as above for 450 centres)			as for 450 centres above	10mm
as above	as above	600	glue/nailed	as for nailed only	300	as for 450 centres above	10mm
					450 centres

Fig 1(a) No vapour barrier Fig 1(b) Alternative to 1(a) Fig 1(c) Vapour barrier

Plywood flooring over battens on concrete

Fig 1(a) No vapour barrier

Fig 1(b) Alternative to 1(a)

Fig 1(c) Vapour barrier