Monthly Archives: August 2012

Moisture Matters #1

As promised earlier, we are delving into the changing world of concrete subfloor moisture testing in as much detail as we can (without driving you totally insane).

Resilient Flooring Installation Standard AS/NZS 1884 has been reviewed and the revised version was published in June 2012. Obviously, if you wish to properly limit your liability, or avoid major implications in the event of a future floor failure, standards should be followed. In the absence of a specific timber flooring installation AS/NZS Standard, 1884 is the most applicable.

Essentially, the revisions have done away with the time-honoured “moisture content <5.5%” measurement. For reasons will we go into in a later post, it was widely regarded as irrelevant or inaccurate. Relative Humidity (RH) is now the required indices, and the wording of the standard strongly implies that measuring RH within the slab is the preferred route. It does allow for reading RH at the surface under some circumstances (where drilling the slab is restricted), but this method is regarded as less accurate, and even the standards themselves acknowledge this.

But first, lets revisit some concrete subfloor basics.


Concrete starts wet, and has to dry. The water/cement ratio generally should be between 40-50% water, but even small increases in water can lead to disproportionately higher drying times. A 5% increase in water can DOUBLE the drying time of the concrete. 10% increase- TRIPLE the drying time. The same thing occurs when the concrete is thicker- drying times increase disproportionately. (CSIRO – Ron Denning Feb 2012). A dry, old slab which has been re-wet for some reason (poor drainage, flooding, no vapour retarder beneath the slab, plumbing failure etc) will take longer to dry than a new wet slab.


For Timber Flooring, in simple terms, moisture migrating to the surface of the concrete breaks the bond between the adhesive and the concrete.

Some argue that the move away from solvent-based adhesives towards lower- VOC water based types has increased failures in recent years. It’s also interesting to note that the higher water content in adhesives can itself contribute to failures- that is, it’s not the water itself but the alkaline solutions in the concrete surface activated by the water, which attack the adhesive and cause it to delaminate.

Such moisture from adhesives has also been known to cause the timber to swell, the problem being incorrectly (in some cases) blamed on the slab. That said, drying slabs are the most common culprit but again, it’s not the water itself, it’s the fact that the water carries alkaline solutions from the concrete, which are the main detriment to adhesion.(CCAA paper April 2007).

Other flooring types, such as vinyl, are also susceptible to their adhesives being re-emulsified by the alkaline solutions. It can get very ugly, in the case of “Sick Building Syndrome”- moisture migration causes the alkaline solutions to break down the adhesive, and the resulting toxic emissions (including nasty substances like butanol and ethylhexanol) can exceed safe levels. It is no small matter.

In the case of Timber Flooring, timber being the most hygroscopic flooring material around (it takes up and releases water at a higher rate than anything- see our other post on that subject), as well as adhesive failure, you have the inevitable deforming of the timber itself to look forward to.


Firstly, if you’re on a 1000 square meter job, an effective MB will cost at least $8 per sqm. This extra cost can skew quotes rather badly and is no small matter.

Secondly, and we are not trying to be alarmist here, but MBs aren’t necessarily a moisture cure-all. In layman’s terms, a MB doesn’t “block” the transmission of vapour, it simply slows it down to a point which the flooring can handle (which will be specified in the flooring or adhesive manufacturer’s spec sheets- that’s another story!). They all have permeability ratings, usually measured in grams per square meter, per 24 hour period.

Which means, that if the RH in a slab is high enough, it might create enough vapour to compromise a MB. What if your coverage rates were not sufficient to create the required thickness? The main thing here is following the manufacturer’s guidelines so that you are covered, or at least supported, in the event of a failure.  

Which brings us back to the need for properly undertaking a moisture test at the outset. A manufacturer might have a tolerance level of <85% RH for their flooring product (adhesive, etc). You can’t expect them to honour a warranty if you don’t know what the RH level in the slab was- even if you apply a MB. 

We’ll get into the methods of testing, and why some are recommended over others, at a later post.

Timber Moisture Stuff

While it’s a particularly damp time of year, especially here in Victoria, the subject of timber moisture and installation has reared its wet head.

If you don’t already own a moisture meter, you should get one. The most common are “electrical resistance” meters, that is, using two pins which need to be inserted into the timber.

However, moisture meters aren’t the beginning and end of the whole thing, as handy as they are. All they do is give you a starting point from which to make the best possible prediction about the timber’s movement in the future.

The key here is to learn about Equilibrium Moisture Content (EMC). That is, the standard moisture content at which the timber will be happy, so to speak, in its given environment (the “expected service conditions”). Some regard EMC as a figure which applies to the timber itself,  while others regard EMC as a theoretical figure, representing the building environment, but which timber will approach from its own moisture condition.

Either way, it’s basic science, and how that information is used produces the same result- namely, whether the timber is ready to lay, and what we can expect it to do once it is.

As we will detail a little further down, it’s not hard to work out the EMC once you know the “expected service conditions”.

The challenge is to determine what the expected service conditions will be, and to what level of regularity these conditions will be maintained throughout the life of the floor. When you turn your heaters off at bedtime, you may have noticed that, in terms of temperature and humidity- what’s outside gets in! Or perhaps your customer is an Eskimo, who will have their house constantly running at a soothing 5 deg C and 80% RH while it’s a billion degrees outside. Our apologies to Eskimos.

Here’s some salient points;

1. Timber is generally released from the Mills at a moisture content of between 9-14% and by the time it arrives to the contractor, it’s generally around 10-12.5%. The key word here is “generally”

2.  Floor boards expand with extra moisture, contract with less, and different density boards will expand at different rates. Therefore, if you install boards with a moisture content of 11%, but the EMC is 13%, they will most probably expand.

Tramex have a good pin resistance meter.

The moisture meter is an essential tool, but it only gets you started. The contractor’s biggest challenge is how to interpret the meter’s findings, and use the information to best advise the customer.

Your first stop should be the Bureau of Meteorology  where you can search the weather data on the property’s region, and calculate a yearly mean temperature and RH (RH is very important!).

You must also take into account the kind of air conditioning the customer’s property will utilize, bearing in mind that this, and the outside weather conditions, will influence each other.

Fortunately, the ATFA have published a very useful paper on this subject, Acclimatisation of solid T&G Flooring . Make sure you real the WHOLE thing, but note that it has a useful EMC chart which will tell you what the timber is most likely to do, once you know the property’s “expected service conditions”. We’ve reproduced it here:

(Note that the timber’s EMC is far more influenced by RH than by temperature). Here you will see that, if the property’s expected service conditions are to be 60% RH and 20 degrees, the timber’s EMC will be 11%. If your tests produce readings of around 9-10%, the timber will most likely expand. The ATFA’s resident guru on timber moisture (and lots of other stuff), David Hayward, advises that the timber may never fully reach the EMC figure. However, it is very important to calculate an average temperature and RH scenario for the building- because it changes all the time, therefore so does the EMC.

The ATFA paper will give you an idea of how much, in terms of mm, the boards are likely to expand (what they can’t tell you is how quickly- that will depend on the species).

So, when you hear talk of “acclimatisation”, know that the devil is in the details. So the timber flooring was stacked, with spacers, in the property itself for a whole four weeks prior to install- does this mean it has been properly acclimatised? Not necessarily! The question is, were those four weeks subject to expected service conditions? Equally, timber only left on site for a few days, but moisture tests to within the calculated EMC, may require no acclimatisation at all.

This is, of course, not taking into account other moisture sources, such as the concrete subfloor-that’s another story.

It’s important to make sure your customer know that their timber floor WILL move, that is as inevitable as death, taxes, and Hollywood cliches. But being armed with this information will ensure that you install timber flooring within an acceptable moisture range, and you can all but eliminate the worst timber movement.

ANZAC Friendship game, Vietnam

As mentioned in a previous post, Lagler Australia are sponsors of the VIETNAM SWANS.

Recently, Lagler’s Cameron Luke took the trip to Vung Tau, the place where it all began during the Vietnam War, and took part in some of the footy festivities as build-up to the traditional ANZAC Friendship Match.

The teams line up to do battle

This year, the friendly was slugged out between the Vietnam Swans and the China Reds. A full report can be found on the Swannies’ website.

A swan practices at the “Lagler End” of the legendary Vung Tau oval.

As for Cameron’s game, he was just glad to survive. “It was oppresively hot” he said afterwards.

Cameron makes it through to the best bit

Spare a thought for the China Reds though- they had enjoyed snow in China three weeks earlier, and now had to contend with searing Vietnamese heat and a pumped up bunch of Swans!

The Reds lost, but as the saying goes, it isn’t who wins and loses. It’s about how much money the matches raised for vital community projects in Vietnam- such as swimming lessons for the kids. They also raised money for some key orphanages. One in particular is run by My Huong Le, an Aussie woman born in Vietnam during the war, and given up by her Vietnamese mother to be raised by a foster family in Australia. She eventually returned to Vietnam, found her mother and established an orphanage in Vung Tau.

We will be posting more about My Huong as we go. Lagler Australia are determined to garner some support for My Huong’s work. Meanwhile, her touching story can be found here.

Vung Tau oval, where diggers first played AFL during the Vietnam War.