Thread: Controlling timber movement

chipboard flooring

Ceramic tiles.

Most books on timber will list some properties, strength, density, hardness and shrinkage from green. The shrinkage is related to the stability, and is a percentage from green to 8 or 12% MC. The less srinkage then generally the more stable the wood. Also look at the difference between radial and tangential shrinkage, a large difference there is worse than just a high but even shrinkage.

So if you look at bluegum (E.saligna) it has shrinkage values of 7% (tan.) and 3.8% (rad.) Compare to Tassie blackwood at 2.7 and 1.3%.

So blackwood is more stable than bluegum. No surprise there
The other figures will let you compare hardness, strength and density.

You can look up a lot of the Aussie wood properties here.
http://www2.dpi.qld.gov.au/hardwoodsqld/7680.html

Cheers

Ian

another rule of thumb could he to look at species that tool makers use. eg ebony, casurina, jarrah, rosewood etc.

eg colen clenton uses ebony and casurina - i understand he buys a "whole trees worth of casuria" and works his way thru it...

cheers

G'day.
Unit of shrinkage.

mm movement per 1% moisture loss or gain.
Blackbutt = 0.3mm. This means that for every 1%moisture loss or gain, Blackbutt that has been Kiln dried will move .3mm per 1% moisture content change.

Thus BBT @ 12% manufacture 80mm cover width.
BBT @ 14% = 80.6mm cover width.

BBT= 0.3mm
S/Gum= 0.28mm
GIBK= 0.26mm
Blue Gum= 0.31mm
Rose Gum= 0.33mm

As usual, excellent info! Thanks all.

Originally Posted by Carpenter

I've just been reading an article in "Australian Wood Review" titled "Why Wood Moves". It makes mention of using species with low unit shrinkage or shrinkage gradient, & so I am wondering if any of the experts out there have some kind of timber species reference that has this info. It would be very handy to know which species provide the best level of stability, particularly with a situation like T&G flooring.

As a timber floor installer, over the years i have noticed that the softer woods seem to shrink more, however all timbers shrink . I should say that all timbers , and i am only refering to tongue and grove, will stabilise to its enviorment depending of the content of moisture in the air. In the buisness of ensuring that a floor wont shrink or expand out side its required working conditions, we need a E.M.C (equilibreim mosture content) to be in effect. All flooring should be kiln dried and arrive on site withn a content of moisture between 9 to 13 percent. Whilst on site, and stacked correctly over a period of about 2 weeks, E.M.C will be achieved. Prior to installation, consideration has to be given in regard to large glass surfaces that will have direct sun shining through it onto the floor for long periods of time. this factor will cause a kiln effect and dry that section of floor out and you will experence shrinkage confined to that area. The same may apply to areas that are exposed to heated areas caused by gas or elec heaters. In my opinion, all species a good to use, we have a rich source of textures and colours to choose from here in Australia, all you need to do is correctly install it with consideration to its working enviorment.

What Larry saws is correct about acclimatization on site, but recently State Forest NSW (Charlie Herbart) has been saying that it is OK to install a floor that has been delivered as the new drying techniques ensure that the flooring is more stable and less likely to be effected by moisture.

Gapping of a floor is more like to happen in a wide board floor (ie 130mm / 180mm +) than a 80mm wide floor as the boards have a greater surface / face area to be effected thus change. Gapping also occurs when flooring is installed incorrectly ie no glue (polyurethane ONLY) or where the subsurface is incorrect.

My own house has 80mm brushbox which was installed correctly and has gapped but the reason is it is cooled in summer to 18deg then heated in winter to 25deg. Gaps are no big deal to me just part and part of having the floor and heat/cooling.

G'day.
Yep.
We dry to suit insitu conditions with an EMC of 10%.

So, laying direct from the pack is fine, provided conditions are right.

If a floor is laid in a location that has a higher EMC, intermediate expansion gaps need to be left every 1000mm across a floor 6 metres or wider.

It takes a pro installer who can read conditions and make an educated guess as to the climatisation needs of the floor.

So many floor problems come from flybynight installers or builders who think floor laying is not important.

Even knowing what I know about timber flooring, I would not install a floor myself. I would get a pro to do it.

This discussion indicates the importance of knowing the moisture content of you're timber, which leads me to another question; whats the best type of moisture meter? There are spike/probe units & I've seen one from Carbatec that uses some other method. Which one would give the most accurate indication of EMC - I'm supposing that the one which can measure deepest would give the best indication?

Originally Posted by Carpenter

This discussion indicates the importance of knowing the moisture content of you're timber, which leads me to another question; whats the best type of moisture meter? There are spike/probe units & I've seen one from Carbatec that uses some other method. Which one would give the most accurate indication of EMC - I'm supposing that the one which can measure deepest would give the best indication?

Good question......I have used a probe moisture meter for years.But recently i have used the rule of thumb of two weeks on site. There is a other meter that has no probes but uses sound waves simular to a depth finder on a boat. all u do is place the meter against the surface , press da button and a digital reading appears. I recon they are cool to use. It is good to hear that installation from the pack is reconised,I have done that a few times just recently with huge sucess, however on one ocasion the boards grew wide ways and closed a expansion gap at a sliding door. I prefer to settle the boards on site for those two weeks because i can get more accuracy at different locations ...what i mean is some times the builder wants me to provide a butt finnish at newell posts or stringers, or i enjoy providing a 3mm to 1 mm finnish line at thresholds , even butt finish them at those arears that require a joinery finish. i can achieve this neatness easly because i know that the timber wont react excessivly, unless there is a mechanicly intro of water. when ever i see a cupping of a board 80mm or 180mm, i know it is water. always is and always will be , you then find the soarce of wter.... a you will find a mop in the corner, to spilt water out of a fridge to a open window and a sprinkler system on automatic. i have seen 100 year old secret nailed hoop pine and is as tightly fitted as the day as it was laid. it all gets down to the installation.... trevor was right when he mentioned about poorly installed floor ...even by chippies. the installer needs to know and understand the science of the wood, he needs to see into the timber and not just look at it. He needs to develop a working relationship with timber and know and understand reactions. The installation of timber is call a finnishing trade, it is furniture. The client dreams and has a mental picture of their floor even before it is built... our job is to give them their dream. Personally, i love working in timber and watching the clients reaction to them walking on their new floor for the first time . I am also a floor sander as well, so i get to see the finnished product as well..............awesome.

Originally Posted by Carpenter

This discussion indicates the importance of knowing the moisture content of you're timber, which leads me to another question; whats the best type of moisture meter? There are spike/probe units & I've seen one from Carbatec that uses some other method. Which one would give the most accurate indication of EMC - I'm supposing that the one which can measure deepest would give the best indication?

The one thing is though........ a good chippie is good to watch his work. I love working along side of carpenters and doing work that gains their aproval.

Here is something else for ya all....... when i know that the internal enviorment of a house or comercial office is going to be under constant refridgated air conditioning...... i will doa site conditioning of the tounge and grove in a refridgerated container.........................u see, airconditioners dry out the timber to much lower levels, down to nearly nothing some times. so it makes sence to gain emc to that air enviorment.i will also make sure the air con is on when installation takes place. The end result is a perfect floor no gapping . You dont even need expansion gaps. The floor stays permantly stable. You can go from cold to hot conditioning with out any adverse reactions. This is only achieveable when the floor is in a totally enclosed and a controlled conditioned site. Offices in big buildings are great for this. NO humidity, the only water is when some one spills a cup of coffe on the floor....

Here is something else for ya all....... when i know that the internal enviorment of a house or comercial office is going to be under constant refridgated air conditioning...... i will doa site conditioning of the tounge and grove in a refridgerated container.........................u see, airconditioners dry out the timber to much lower levels, down to nearly nothing some times. so it makes sence to gain emc to that air enviorment.i will also make sure the air con is on when installation takes place. The end result is a perfect floor no gapping . You dont even need expansion gaps. The floor stays permantly stable. You can go from cold to hot conditioning with out any adverse reactions. This is only achieveable when the floor is in a totally enclosed and a controlled conditioned site. Offices in big buildings are great for this. NO humidity, the only water is when some one spills a cup of coffe on the floor....

To true but builders don't understand the that the AC needs to be hooked up and working prior to floor installation. Its hard enough getting all the wet trades finished. (floor/wall tilers timber floor nightmare).

A major Timber floor company in Sydney has a big flash show room with a wide board floor sure enough there is significant gapping of the floor due to AC (upto 3mm per row)

Today were laying a 6in floor in an extension it butt end on to a floor that was laid within last 5 yrs. when we lined the rows of boards up the first couple of rows matched no problem, but as went further across the opening the new floor was about 3mm out from the existing. This is because the existing floor had opened up over the last 5yrs. Result we laid the new floor with a small spacer so that the boards look like a continuous run dived by a 3mm flat bar,