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Hi there, I have had prefinished engineered timber flooring installed for about a year and there are end to end board failures in many areas resulting in vertical movement of these boards. Do you know if this rectification method is acceptable industry standard and is it currently being used in Australia? In addition, there was meant to be a layer of plywood installed between the battens and floorboards. For whatever reason, this plywood layer is missing. The installer has refused to accept the flooring defects are due to this missing supportive plywood layer and is only willing to spot rectify the affected and moving boards by fixing in a long nail to the concrete subfloor and then pouring in glue to push up the sinking boards. I am wondering also whether popping and squeaking noises from loose boards in other areas are caused in relation to the missing layer of plywood. Could you please assist me in recommending someone who is able to carry out destructive testing of the installed boards to investigate whether they are strong enough to withstand residential use when installed directly over battens without a layer of plywood. I am from Adelaide, South Australia. Thank you for your time and assistance.

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Most engineered timber flooring is designed to be laid over a solid base. In your case the proposed rectification method does not sound ideal. We suggest you obtain an installation guide from the manufacturer or importer of the flooring to see how it should be handled. The Australian Timber Flooring Association (ATFA) has published a comprehensive guide to engineered flooring available for download here. The guide points out that "There are a limited number of products that can be fixed direct to joists or battens [ie. without a plywood or particleboard underlay]. For the specifics relating to the preferred installation method, the product supplier’s installation recommendations need to be viewed and then recommendations adhered to".

Select blackbutt flooring was installed throughout the house 2 years ago. In only 1 room, solid black marks have appeared randomly in the last year. The patches are up to the size of 2, 20 cent coins. This room has old hardwood joists which have been retrofitted with a foil sisalation stapled to the u/side of the joists. The underfloor area is not especially damp. Could these marks be a mould and should I remove the sisalation to allow the floor to breathe more? Is there anything I can do to clean the marks up?

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If the marks took a year to appear it sounds as if they are related to site conditions rather than a fault in the timber. When you say the underfloor is not "especially" damp perhaps it isn't quite dry either. The marks are probably not mould but possibly tannin that moisture is bringing out of the wood. Are you able to increase the flow of air under the floor to remove any build-up of moisture in the underfloor space? If moisture is rising from the ground, removing the sisalation will only allow more moisture to be absorbed into the flooring, unless ventilation is improved at the same time. Perhaps a site inspection is warranted as it's hard to be sure that moisture is the problem without testing the timber. If the flooring is exposed to moisture from below one would expect to see some swelling or cupping in the floorboards. With regard to removing the marks, you will need to identify the cause first otherwise the marks may return. Also the required treatment will depend on whether the marks are mould or tannin stains, and whether the flooring is sealed or unsealed. 

Hi, We're looking at using CLT for a house in Sorrento starting next April. I'm interested in the suitability of a polished screed (30mm?) as a finish to go over the CLT floor panels. Does anyone have any experience as to whether this would be a suitable option? I'd also thought of Resin finishes, but am concerned about flex/shrinkage and subsequent cracking. We'd ideally like a polished concrete effect for the flooring over the top of the CLT panels, but are steering away from timber floor boards.

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Our advice is to treat this in the same way as a mortar bed laid over particleboard or plywood in a wet area. The procedure is too detailed to reproduce here, but you will find it outlined in the manuals issued by particleboard producers. Of course this will be subject to a structural check to make sure the CLT is suitably sized to carry the extra weight.

hi Dr. Fred Moshiri,
I recently found out about your research on timber structure from Jane Armstrong and I am deeply inspired by your work.Initially I gained an interest in this subject from working at Taree as a junior engineer. A few questions was raised for me regarding the market for Wood Solutions. Could you kindly comment on the below queries?

How you think wood solution will change engineering?
How would wood structures compare to other structures such as steel (Counsider that fact that Australia is a mining country, it'd be wise to use metal rather than wood?)
How would the cost compare to other structures?(LendLeash shipped their timber from Europe for Barangaroo,Sydney Towers)
What infrastructures do you think would be most suited for wood solutions?
How will the issue of sustainability be tackled by providers of wood solutions?
And finally will there be a seminar soon, I'm keen to listen to your ideas !

Cheers !
Sunny W.

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Dr. Fred Moshiri is actually based at the Timber Development Association, so you will need to contact him there. His LinkedIn profile gives contact details here:

What are the standard hardwood timber sizes?

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Sizes may vary a little from one producer to another, but the Boral size range would be fairly typical. You can access their flyer here. Note that the seasoned (kiln dried) range is the same as the range of structural pine sizes, ie. 90 x 35, 140 x 45 etc. The corresponding sizes in unseasoned ('green') timber would be 100 x 38, 150 x 50 etc, less a sawing tolerance of 3mm. Unseasoned sizes are generally a soft metric conversion of the old imperial sizes, on the basis that 25mm is approximately 1 inch, ie. 100 x 50 = a '4 by 2'.

What is the span for 90x35 on flat ceiling batten?

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There are no span tables in the Supplements to Australian Standard 1684, Residential timber-framed construction, that are specifically for ceiling battens. However, we consider Table 32 for roof battens would be suitable. Appendix A of AS 1684 (Table A1.2) gives typical masses for 10 mm plasterboard of 7.5 kg/m², and 13 mm plasterboard 10.0 kg/m². The 'sheet roof' section of Table 32 is based on a roof mass of 10 kg/m², as stated in the footnotes to Table 32.

We have an existing Tallowwood flooring internally which has been waxed or oiled (I think), and is scratched. Would you know what the most likely (if it was the most appropriate) finish would have been (ie not polyurethane), and what the best treatment would be to conceal the scratches?

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It's difficult to know what your floor might be coated with. Oil would give a dull finish unless freshly applied. If it is waxed you might be able to scratch off some wax with your fingernail since wax tends to build up with repeated applications, whereas oil soaks into the wood. In any case, wax will probably work best to conceal the scratches - oil might actually accentuate them. Companies such as Whittle have suitable products for waxing floors. You can contact the distributor, Austral Flooring, via their website here: Note that once a floor is waxed it is very difficult to apply a polyurethane since the wax prevents it from bonding to the wood.

Hi, do you have publications regarding the pros and cons of staining an interior floor?

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We don't know of a publication that specifically addresses this issue, but it's certainly possible to stain a timber floor. The main 'con' factor is that it's more difficult to resurface the floor later if the stain wears through in high traffic areas. A clear coating can sometimes be touched up by simply re-coating the worn area, using the tongue and groove joint as a natural boundary. If a stained floor becomes worn it's usually necessary to resurface the whole floor. So if you intend to stain a timber floor it's advisable to place rugs or mats in areas where there is a lot of foot traffic, or where furniture is moved around, eg. chairs around a dining table.

Are there any resources on the effects of fire on timber and repairs recommended?

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The effect of fire damage can be assessed according to Australian Standard 1720 Timber structures, Part 4: Fire resistance for structural adequacy of timber members.

Could you please tell me which of the suppliers of Tasmanian Oak listed on your web site are located in the Central Coast of New South Wales? If none, then in Sydney. Thanks.

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You don’t specify whether you are looking for flooring, or just PAR sections of Tasmanian oak, but Walker Bros should be able to help. You will find details on their website at this location:


Can you recommend the use of a 150 wide pine strip flooring (match existing t&g on joists) over plywood on a Concrete slab - cannot source a supplier and all install info relates to narrower boards?

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Floorboards of 150mm should be available from timber merchants in your area who deal in Baltic pine. It’s a little wider than the 135mm width, recommended as the maximum for fixing to a plywood underlay, but should be OK if adhesive is used in conjunction with mechanical fasteners, eg. staples. For a detailed specification on fixing strip flooring to plywood, refer to our Technical Design Guide no. 9, available for download here. Note that you will have to log in to access the guide. Fixing to a plywood underlay is covered on p. 28 onwards.


With the engineer specifying a GL10 (F11) Durabeam of 378 x 110mm (7m in length) is there a way for me to find out what section I would need for an GL21 Spotted Gum Glulam alternative beam?

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It's possible the supplier of the GL21 glulam has span tables which would allow you to check the size needed for your particular application. However, unless you are familiar with using span tables it might be better to go back to the engineer who specified the GL10 beam and ask how GL21 would compare.

Hi Wood Solutions...

I am an architect trying to find industry definitions for "select grade" + "standard grade" timbers, for use in strip timber floors + internal joinery.

I have looked on your website, but am unable to find.

Can you please email me a link or PDF to answer my query.


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Grades of hardwood joinery timber are defined in Australian Standard 2796, Timber - Hardwood - Sawn and milled products, Part 2: Grade description. The Standard provides for three grades, Select Grade, Medium Feature Grade (Standard) and High Feature Grade. You can, of course, add requirements specific to your project by agreement with the supplier. For example, you might specify 'timber flooring to comply with Select Grade as described in AS 2796.2 but with knots limited to 10mm in diameter'.

Can I seal or paint particle board flooring. with what?

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Particleboard flooring can be sealed with the usual range of floor finishes (polyurethane, oil, etc.) but it is more absorbent than timber. This means it is likely to take a number of coats to build up a high gloss 'natural' finish, if that is what you want to achieve. If you don't want a clear finish, paving paint will give you an opaque finish but will show scuff marks and scratches more than a clear finish.

An architect has specified (and used) Western Red Cedar for the interior of a commercial building.
The private certifier for the project wants "the fire hazard report that was originally prepared by a nationally accredited body", that shows that Western Red Cedar is a Group 3 product.
I have sent the information that i usually send...but it is insufficient for this certifier.
Please can you assist, with the requested report, as he will not sign off the project without it.
Many thanks
Russell Mead

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The attached report shows that western red cedar in a minimum thickness of 9mm achieves Group 3 status.

Do you have any recommendations for internal timber flooring floating on structural ply floor attached to concrete FOR DIFFERENT ENVIRONMENTS. In a hinterland environment close to the coast where humidity can get quite high from surrounding trees, and a fireplace will be installed within the premises,which timber flooring type would be recommended : real timber hardwood, engineering timber flooring or bamboo???? If you could respond or call 0418721982 that would be appreciated.

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Engineered timber flooring is generally the most stable product since it is manufactured like plywood with the grain changing direction in each layer. Nevertheless, for best results any flooring product should start with a moisture content suited to its environment. You will find some guidelines in a technical data sheet produced by Timber Queensland titled Timber Floors - Pre-Installation Assessment. Copies can be downloaded by writing TQL 17 in your browser. You will also find Wood Solutions Design Guide #09 helpful. It can be downloaded here.

We are laying 19m x 80mm jarrah T&G boards to a split level floor with one step and a landing which is 1.5m wide at one end and reduces to 1.1m at the other end. The step nosing is therefore fixed at an angle and the landing floorboards are to be fixed at 90 degrees into the groove of the nosing.
Because the nosing is fixed at an angle the tongue of the boards do not fix square into the groove at the back of the nosing.
What in your opinion would be my best option?

Thanks in advance

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Thank you for sending the sketch. We see now what the layout will be. However, if the floorboards are laid in the direction of the arrows, the ends of the boards will butt into the nosing from both sides. Floorboards don’t generally have a tongue on the end, so when they are cut to the required angle they would just butt up tightly to the nosing.

I want to have a European Oak floor stuck directly to the concrete slab floor in a family room. The room is about 5 metres wide. Please advise how much space needs to be left each side of the floor to allow for expansion - I assume this would be corked.

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Floorboards only expand and contract noticeably across the grain, not along their length. This means expansion gaps are only needed at walls parallel to the floorboards.

The Code for Residential Timber-Framed Construction calls for a minimum 10 mm gap, plus an intermediate expansion gap for floor widths over 6 m. The need for expansion gaps varies according to the local climate and the initial moisture content of the timber. For example, dry timber installed in a humid climate where indoor conditions are uncontrolled may expand.

In most parts of Australia, timber that has been properly kiln-dried and acclimatised is unlikely to expand if installed onto a dry concrete or timber base, in a controlled indoor environment. Nevertheless, expansion gaps are a useful precaution.

Gaps at the sides are usually covered by skirting boards and do not need to be filled with cork. Intermediate gaps can be filled with a compressible material such as cork, or covered with a decorative brass strip.

For more information about the design, construction and maintenance of timber flooring, download the free WoodSolutions guide Timber flooring – design guide for installation.

Floorboards, Expansion gaps, moisture content, skirting boards

I am preparing to lay 80mm brushbox flooring on a particleboard platform floor secret nailed with adhesive.I have bostik ultra set in sausage form and 15 gauge x 38 mm staples. How is the adhesive best applied and what c/c should I be stapling?

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To secret fix 80 x 19 flooring to particleboard, space your staples at 450 mm centres. The adhesive should be applied in a zigzag pattern to achieve approx. 25% glue contact area. Apply the adhesive midway between fixing points at 90° to the length of the boards to minimise possible squeaks and provide secure fixing.

For more information about the design, construction and maintenance of timber flooring, download the free WoodSolutions guide Timber flooring – design guide for installation.

Brushbox flooring, Secret nailing, Particleboard, Adhesive, platform floor, particleboard

Hello, I am considering using WA Karri as a solid timber floor. I have heard conflicting reports that Karri "moves" a lot more that other similar timbers (eg Sydney blue gum, Jarrah).

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When we talk about timber products "moving" we are referring to the swelling (or shrinkage) that takes place with a change in moisture content. If there is little or no change in moisture content, there is little or no shrinkage.

Timber responds slowly to changes in atmospheric humidity, particularly if it's sealed, so if there are a couple of dry days followed by a couple of wet or humid days, there probably won't be any movement at all.

If there is a prolonged period of dry or damp weather, it's true that karri "moves" slightly more than some other timbers, but the difference is small. Australian Standards quote movement figures of 0.3% of the width of the board, per 1% change in moisture content for jarrah, 0.35% for Sydney blue gum, and 0.4% for karri.

This means if there is a 2% change in moisture content from summer to winter, a 100 mm wide karri floorboard is likely to "move" by up to 2 x 0.4% x 100 mm = 0.8 mm.

The most important thing is to make sure the flooring has a suitable moisture content when it is installed, so movement is kept to a minimum. For most of the southern parts of Australia the moisture content should be in the range 10% to 12%, but this may vary depending where you live. Your timber supplier and/or installer should be able to carry out some random checks with a moisture meter to confirm that the timber is in the right range.

For more information about the design, construction and maintenance of timber flooring, download the free WoodSolutions guide Timber flooring – design guide for installation.

Flooring, Karri, Blue Gum, Jarrah, Swelling, Moisture content, shrinkage

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