Solid Timber Flooring Installation Overview

Flooring Installation Overview

Welcome to our installation guide for solid timber flooring and decking products. Australian species timber installation is dependent on following several guidelines below.

While these guidelines will prove useful, it’s important to remember that installers need to remain in compliance to all BCA requirements, Australian Standards, and other best installation practices.

Moisture and humidity thresholds for underfloor and subfloor must remain within AS 1684 and BCA requirements. Don’t rely exclusively on this guide, especially when it comes to observing any and all safety protocols.

Qualified professionals should always, whenever available, be used to install timber flooring, including any sanding or finishing needed. Licensed carpenters and builders are ideal for installing these hardwood timber materials.


  • Ensure you read all instructions completely prior to beginning any installation.
  • Plan your time accordingly and inspect all materials for defects or faults before you begin installation.
  • As colour and feature will vary naturally in timber, boards will need to be mixed across the installation floor.
  • Your only requirements are your imagination and desire.
  • If you encounter any issues either before laying your timber material or during the installation, stop and discontinue. Contact your timber manufacturer immediately in order to learn how to proceed.

Solid Australian Hardwood Flooring

Installation guidelines for the following solid timber flooring types:

  • 19mm Solid Hardwood Strip Flooring;

  • Overlay Solid Hardwood Flooring;

  • Parquet Flooring; and

  • Hardwood Decking

Please note: this guide does not contain information regarding specialty floor materials such as sports flooring or specific materials related to some commercial applications.

Solid timber floor material is an excellent choice for indoor applications in both residential and commercial buildings. However, when it comes to areas with high levels of moisture such as bathrooms or laundry rooms, you should choose a different material. In the case of any installations over subfloors with radiant heating systems, contact your manufacturer for specific instructions.

19mm Solid Hardwood Strip Flooring

Solid hardwood strip flooring a minimum of 19mm thick is manufactured to be laid upon plywood, battens, or joists over concrete. This material can also be nailed directly to timber flooring that has already been laid. Surfaces are stable and continuous thanks to tongue and groove joints on butt ends as well as both sides of each board in order to reduce waste and eliminate needless cutting. Ends need not fall directly over a batten or joist thanks to end matching. Boards as wide as 130mm can be either top nailed or secret nailed. If your board is 85mm or wider, please refer to secret nailing procedures detailed below. Boards 180mm wide need to be top nailed as described in AS 1684.2.

Appropriate subfloor types

19mm hardwood strip flooring is appropriate for any subfloor type that is clean, dry, flat, level and structurally sound. These include:

  • Strip timber floors already laid;
  • Particleboard, plywood or other sheet flooring;
  • Concrete; and
  • Joists and bearers.

Overlay solid hardwood flooring

Overlay solid hardwood flooring ranges from 10mm thickness to 13-14mm thickness. A solid non-structural hardwood, overlay is a strip flooring material designed to be installed upon solid subfloors.

Available in either 80mm wide or 130mm wide, overlay flooring provides stability thanks to it’s tongue and groove construction.

Appropriate subfloor types

  • 80×10 or 80×13 concrete slabs
  • particleboard, plywood, or other sheet flooring
  • strip timber floor already laid.

Better Parquet Flooring

Parquet flooring, designed to be laid upon particleboard, plywood, or concrete slab flooring, is a solid hardwood timber floor material that comes in solid blocks.

With dimensions of 260mm x 65mm x 18mm, parquet flooring can be used to create attractive designs and patterns by alternating timber species. 65mm square “centre dots” can also be laid individually in order to vary patterns further.

Appropriate subfloor types

Parquet flooring is appropriate for any subfloor type that is clean, dry, flat, level, and structurally sound flooring similar to:

  • Plywood or similar sheet flooring
  • Concrete slabs
  • Acoustaply

Better Hardwood Decking

Better Decking is a solid hardwood timber that is intended to be used in outdoor environments. This product is laid directly upon joists and structural bearers. Additionally, it is appropriate for seating, gates and fencing as well.

This precision milled product features boards with smooth finishes on both sides and rounded edges. A number of widths are available.

These installation instructions are not appropriate for commercial decking or any specialty applications.

Appropriate subfloor types

Hardwood decking is designed for structurally sound joists and bearers as determined by the Building Code of Australia and Australian Standards AS1720.

  • Screws or nails should fix decking directly into hardwood joists and bearers.
  • Timber or steel posts can be used for fencing applications. Decking can be screwed into these posts.

Preparing to Install Solid Hardwood Flooring

Hardwood Properties

Hardwood Timber is hygroscopic. This means that timber will both absorb and expel moisture in the ambient environment depending on local weather and climate.

Timber that absorbs moisture will expand; the opposite is true as well, in that timber will contract as it expels any accumulated moisture. This means that atmospheric moisture conditions, whether natural from weather or artificial such as from air conditioning or inadequate ventilation, can result in timber flooring materials expanding and contracting. Take care to evaluate an installation site before laying floor materials.

Work sites should be maintained and kept in ideal environmental conditions as a result. Additional concerns include providing timber flooring material enough time to acclimatise to a local environment if necessary. Adapting to specific conditions is often a requirement to safeguard against installation problems.

Before you install

Prior to installing your timber floor, be sure to examine the suitability of your site conditions. Timber floors must be installed only in buildings that have been weatherproofed. Projects should be near to complete before installing floors, as this will prevent damage to new floors from heavy traffic.

Construction such as wet trades, exterior cladding, all external windows and doors, and roof need to be completed before installing a timber floor. Storm water systems also must be complete, or at least effective in directing water away from subfloors.

Acclimatisation of Solid Hardwood Flooring

As a natural product, timber can and will expand and contract with environmental changes. Ambient moisture content affects timber flooring. Timber’s moisture content is measured by the percentage of water within the material in comparison to the material’s weight with no water present. Humidity and temperature changes in the air will have a direct result on this moisture content.

It’s normal to have small seasonal changes in timber floor materials. Dry periods can and do lead to small gaps. This is natural and not a defect. However, to ensure hardwood floor movement resulting from moisture fluctuations is minimised, it’s essential to both lay and fix timber flooring that is already close to the environment’s average moisture content.

The following information provides guidance on assessing sites for moisture content and acclimatising solid hardwood flooring materials for ideal results.

Hardwood Flooring Installation. Assessing a Site’s Climate

Every installation site should be assessed before a new timber floor is installed. It is crucial to understand what the relative humidity of a site will be in the long term, as this has a major impact on whether timber flooring material will lose moisture and shrink or if it will take in moisture and expand.

Seasonal changes will be minimal if your timber flooring’s moisture content is close to the site’s relative humidity in the longer term. If there are significant differences between these figures, however, seasonal changes due to moisture content differences can prove problematic.

Hardwood timber flooring materials are typically kiln dried. Moisture content, as regulated by Australian Standard AS2796, is anywhere from 9% to 14%.

A Hygrometer is necessary for measuring relative humidity onsite. Both relative humidity and temperature need to be noted before installation and after.

Local climate information can be obtained from the Australian Bureau of Meteorology website at This will provide you with the equilibrium moisture content, or EMC, for each Australian climate. This figure will reveal timber’s moisture content relative to specific set temperature and relative humidity conditions.

Swelling and shrinkage are naturally higher in locations where there are greater seasonal variations. Regions where high levels of seasonal variation will need to be taken into account, requiring higher allowances for floor expansion upon installation.

Another key factor to reduce hardwood timber cupping and expansion is the amount of subfloor ventilation present at an installation site. Underfloor humidity and subfloor moisture need to be in compliance with requirements set out in AS 1684 and the BCA. High humidity subfloors will result in flooring materials that will absorb this moisture, leading to expansion.

Digital Hygrometer for measuring relative humidity and moisture content in timber

Digital Hygrometer measures relative humidity and moisture content

Important Subfloor Issues

  1. Underfloor humidity and subfloor moisture levels must be in compliance with AS 1684 and BCA guidelines.
  2. There should be no obstructions to any air vents.
  3. Size and number of air vents need to meet BCA requirements at the very minimum.
  4. There should be adequate drainage for the ground level under any flooring
  5. Subfloor grounds need to be level, flat, and clean of any detritus or debris

The ground below subfloors can benefit from being sealed with impervious membranes. Vapour barriers or 200-micron plastic sheeting.

This sheeting should be continuously taped with an overlap of 200mm. With subfloor conditions subject to change, sealing in this manner can provide high levels of performance improvement for timber floors installed above.

Internal Environmental Assessment

Prior to installation, the internal micro-climate needs to be assessed. Within any building, different climates can and do develop and differ from room to room, and this can cause the same flooring to respond differently depending on where within the dwelling it was installed.

Appliances that vent warm air, air conditioners, refrigerators, fireplaces, or rooms with large glass windows can all lead to the creation of micro-climates within a dwelling. Two storey construction and the aspect of the house can also have an impact, leading to timber flooring expanding and contracting. Floors exposed to high levels of direct sunlight either during installation or after need to be protected. Coolers that work on evaporation raise relative humidity by adding moisture to the air, increasing moisture content in flooring material higher than it would be otherwise.

You should also consider how a floor will likely react after installation. Minute differences in board moisture content as they are being manufactured can be as high as 5% under Australian Standards. Variable house conditions such as rooms that face south instead of facing north, will also have an impact on board size and width.

Figure 1.0 – A simple guide to whether acclimatisation is necessary

Figure 1.0 – A simple guide to whether acclimatisation is necessary

This means that it can be expected to see most boards develop small gaps at their edges. This is especially likely to occur during the dry season. These gaps are unlikely to be uniform but will be different across the flooring material.

In situations where the ambient moisture is lower than the moisture content of your timber, there may be moderate shrinkage. Using wider strip flooring, such as 130mm wide boards, will lead to larger gaps than if you had laid 85mm wide boards instead.  Air conditioning systems that have been installed after laying boards may increase shrinkage gaps if these systems lack humidity control functions.

Regardless, there will be some movement after laying a timber floor, as the new flooring material adjusts naturally to the climate. While some floor finishes may have an impact on how much change may occur, these finishes won’t outright prevent these subtle changes. In regions where seasonal changes are more pronounced or greater movement is expected, take steps to prevent flooring finish acting like an adhesive. Moderate shrinking can, in this case, create wide gaps between groups of boards or even cause some boards to split.

Acclimatisation and Moisture Content at Installation

Australian Standard AS2796 states that hardwood timber must be kiln dried to between 9% and 14% moisture content.

Acclimatisation may not be necessary prior to installation if your flooring’s moisture content is close to the expected average moisture content for the work site. In more dry conditions such as buildings with air conditioning or areas further inland, or in more humid conditions such as higher elevations or coastal regions, you may need to acclimatise your timber to your site.

Acclimatisation allows your timber’s moisture content to partially equalise with the ambient environment whenever the differences between the two are great enough to warrant the procedure.

This process can vary in time according to tree species, making it important to monitor progress on a site-by-site basis. Each specific board needs to be exposed to the ambient atmosphere for acclimatisation to be effective. This means all packs need to be opened and then stacked back together so that there is free air flow between every piece of flooring.

The effectiveness of acclimatisation can be hindered if an air-conditioned site does not have its air conditioning active during this process. Likewise, sites that are normally dry must not be experiencing a period of wet weather.

Once the moisture content of the flooring material is equal to the environment’s relative humidity, acclimatisation is complete. Weather conditions and timber species can alter the amount of time needed, but 14 days is sufficient in most cases. A timber moisture meter will be needed to ensure that your flooring material has reached the appropriate moisture content.

This reading can then be compared to the Relative Humidity (RH) using Table 1.1.


Table 1.1 Relative Humidity

Acclimatising Parquet and Overlay Solid Hardwood Strip Flooring

Parquet flooring and overlay solid strip floor material need to be acclimatised after installation. Leave these flooring materials for 14 days, unsanded, before any sanding and/or coating.

In more dry environments, this can lead to gaps forming between boards. Any of these gaps can be filed with timber flooring putty if deemed necessary. More humid environments, meanwhile, necessitate the use of extra expansion gaps to take swelling into account. Exercise caution under these conditions.

Inspection and Preparation of Site and Subfloor Surface

1. Visually inspect surroundings for moisture caused by rising damp, leaky ceilings, laundry or bathroom overflow problems, window seal leaks, or pipe leaks. Evidence of moisture ingress needs to be investigated and remedied.

2. Subfloor areas must be dry and clear of all debris and contaminants. This includes sawdust or metal shavings, oil, grease, paint, and anything else.

3. Subfloor must be fully scraped using a wide blade scraper. This will remove all mortar excess, residues from plasterboard setting, or cement render spoil.

4. Ensure concrete slabs are flat. Australian Standard AS3600 – 2001: Concrete structures requires a maximum deviation of +/- 3mm over a 3m radius. Any deviations in excess need to be filled with self-levelling compounds or ground down to the appropriate level. If timber flooring is being installed over battens, you have the option of planing these battens down or using packers to remedy any unevenness in concrete subfloors.

5. AS1884 – 1985 requires concrete subfloors to have less than a 5.5% moisture content. In instances where moisture content is higher, vapour barriers need to be applied. Additionally, the use of builders plastic (200-micron membrane) is recommended before installing plywood substrate or battens. This reduces the risk of timber flooring absorbing moisture from the concrete slab. This plastic barrier should reach 75mm up the walls of the subfloor and should have 200mm of overlap. Duct tape should be used to seal joins. Follow manufacturer instructions when installing vapour barriers. Use compatible adhesives.

6. Plywood or particleboard substrates or existing timber floors need to be both clean and flat, sanded where necessary. Any plywood used needs to be in compliance with AS/NZS 2269 Part 0.

7. Installation over a platform floor or joists and bearers requires high levels of subfloor ventilation. High humidity areas underneath timber flooring can lead to high levels of swelling, cupping, and expansion. Minimum ventilation levels should meet Building Code of Australia standards, though high humidity areas may need more robust ventilation to increase subfloor ventilation. Vents need to provide opportunities for subfloor cross ventilation and should never be placed on just one side of a structure.


Ensure that all your construction materials are free from any defects or faults before beginning installation. Boards should be mixed across your floor by feature and colour. This is at your discretion to create the aesthetics of your choice. If you encounter problems prior to or during the installation process, stop and contact your manufacturer for instructions or advice on how to proceed.

Control Joints and Expansion gaps

Always plan perimeter fixings and expansion gaps prior to beginning installation. With timber being hygroscopic in nature, moisture content changes will lead to your flooring both expanding and contracting. This makes it essential to have expansion gaps at the perimeter walls and wherever there are obstructions in order to provide space for the floor to move. Not enough gaps, or gaps that are too small, may result in your flooring becoming buckled or deformed.

Minimum expansion gaps, whether at an obstruction or at a perimeter wall, should be set at 12mm.

Australian Standard AS1684 requires intermediate expansion joints for floor widths more than 6m in domestic applications. In more humid locations where you need even extra allowance, consider clamping pressure.

An alternative to this would be to ensure that more expansion gaps are included every 800mm to 1000mm, which can provide the same amount of spacing. Cork expansion joints should protrude 2mm above the floor surface at installation, with the excess being removed during sanding. The exception to this is at the perimeter, where cork should be installed level with your timber flooring. You can use thicker beading or skirting or undercut plasterboard walls to increase expansion gaps. Meanwhile, the rule of thumb is to allow room for as much expansion as possible during installation.

It is best to place expansion joints in line with an internal wall or at a doorway. These joints are ideal for breaking larger floors into smaller, more manageable sections.

Specialty Flooring Considerations

Commercial applications, sports floors, and other specialty applications may need additional expansion gaps. This should be determined on a case-by-case basis.

expansion gaps timber flooring installation

Acoustic Underlays

The number of acoustic underlays available on the open market is large. We recommend Acoustaply, one that is specifically manufactured to be compatible with the entire range of Better Timber Flooring. Using Acoustaply, will ensure your flooring underlay either meets or exceeds BCA requirements of 62 Lnw+C for solid timber underlays. Alternative product systems in compliance with AS ISO 717.2 – 2004’s ISO 140.6 and 140.48 are similarly ideal.

Always follow all installation instructions as provided. If you have questions, contact your manufacturer.

Installation Instructions for Solid Hardwood Flooring

  • 19mm Solid Hardwood Strip Flooring;

  • Overlay Solid Hardwood Flooring;

  • Parquet Flooring; and

  • Hardwood Decking

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