Welcome - Timber acoustics

Recycled timber as far as the eye can see!

As we receive a large number of enquiries concerning the noise level of timber floors we have done a bit of research in this newsletter to put this issue in perspective. The problem is solvable, and the available solutions are not that expensive.

Recent visitors to our warehouse will have noticed that we have a warehouse full of demolition timber stock. A few people are talking about this latest recovery so you will need to hurry into our showroom if you want to see the full range of new recycled floors that we have available. One of them has already sold out!

It is not just the stunning recycled floorboards that are catching everyone's eye - we have also acquired a number of 6 metre long, hand hewn 190mm x 190mm posts. We are wire brushing them so they retain their character. So if you have an idea for building that pergola or gazebo and want to buy-in a bit of character you had better move quickly. You don't find character like this growing on trees!

On a separate matter, Luke Commons who used to work here has returned to Ironwood. He's a terrific addition to our team, very knowledgeable about timber and a timber flooring specialist. Though he is a Kiwi we are glad that he's onboard, even while the World Cup is on!

Message for architects, designers and renovators

Timber floors appreciate, carpets depreciate!

Have you ever noticed that ads for houses often mention polished wooden floors but rarely mention carpets.

The reason is not just attributable to the exquisite beauty of timber. Timber floors appreciate, carpets depreciate!

Furthermore, when it comes to antique timbers, our Australian recycled hardwoods have just been discovered, they are 'flavour of the month' when it comes to floors and outdoor landscape feature timbers. They also look better than any new timber you will ever see and have a bit of character and charm from their earlier life - well that's my opinion and I'm sticking to it!

Strange and fantastic how people in 2003 are discovering the beauty of timbers that are hundreds of years old.

Keith Mackenzie
Managing Director

October specials!

• HAND HEWN POSTS 190 x 190 recycled timbers, reds and creams, plain & wire brushed, up to 6m lengths
  $150 per metre
• 80 x 19 recycled floors, plain end, in creams and reds, STUNNING VALUE
  $65 per sqr mtr

Feature story

Acoustic Solutions for Floors

Timber floors can be quiet as well as attractive.

The Building Code of Australia currently does not specify an acoustic standard, does not have a minimum standard nor does it require floors to be totally noise free. So why are we talking about acoustics? The BCA is about to introduce a minimum level of sound attenuation for all multi-tenant buildings and residences which will really put the cat amongst the pigeons.

Right now the only thing we know is that we have different body corporate standards in each state and that in Sydney an IIC rating of 55 is considered to be acceptable by most body corporates.

The other acoustic thing which is changing is that our Australian 'scales' are being brought into line with European DIN standards. The old measures, which are:

• IIC - onsite 'Impact Insulation Class' measurement - the higher the number the better the rating; and
• STC - 'Sound Transmission Class' measurement - the reduction in airborne sound transmitted through a floor or wall;

are also about to be superceded by the new European measures:

• L'nTw - replacing the IIC. The lower the number the better the acoustic rating;
• Rw - replacing the old STC (similar numbering system).

There are primarily 2 types of sound that acoustic engineers focus on when it comes to floors:

1. Low frequency sounds, such as footsteps. Impact vibration also comes from the bass of a stereo as well as things like vibrating washing machines and dryers that have lost their rubber legs or are leaning directly against the wall. To reduce the sound reverberating through floors they need a degree of separation to reduce the impact vibration which resonates through the building. This is best achieved by separating a timber floor from the concrete structure, using acoustic rubbers that do not crush over time and always rebound to their original thickness.
   
   
2. Airborne sounds, such as voices and music - they are best treated by using materials with mass, such as concrete, CFC sheeting and batts - anything which has the ability to absorb or reflect the sound wave reverberations.

Dealing with the new standard

The new BCA standards will obviously specify an impact insulation class that is considered to be reasonably quiet - there will however be no pleasing some people. The new provisions will ensure builders and developers don't build a timber floor that is pinned directly to the concrete slab. It is also likely that body corporates will start altering and measuring their own tolerances so this whole issue is going to escalate.

Most building designers are currently working on IIC rating of 55 - 60 as their benchmark. Striving for an impact rating above 60 for tiles, timber, vinyl, parquet and other floor coverings becomes exponentially more costly for every point above IIC 60. Additional layers of deflection are required to improve such ratings, which also reduces the 'floor to ceiling' height.

Floating floors are not a new concept. What is however becoming more of an issue is the quality of foams, rubbers, foams and polyesters they use which do not keep their original thickness but crush over time.

Solving the riddle

There are a few variables in the acoustics equation, the sum of which determines the acoustic effectiveness of a floor system:

1. Mass of the Subfloor. Since much of today's construction is on concrete slabs, buildings are assured of a decent airborne sound rating. It's the sound deflection and physical separation that requires attention. The thickness of the slab is the most important criteria for a good acoustic flooring system. A 170mm concrete slab provides an STC rating in the low 50's.
   
   
2. Ceiling Height and its connectivity to the above sub-floor. A sheet of 13mm gyprock nailed directly into the underside of joists or a slab will give little additional benefit to the IIC rating. However, an acoustic plasterboard ceiling fixed to a rubber mounted track system, suspended 100mm under a slab with polyester insulation in the ceiling cavity, can yield a benefit of 5-8 IIC points. This cavity can be used for other building services if built into the design.
   
   
3. Finished Floor Level (FFL) that architects and designers have allowed for an acoustic timber floor to be built to. It is difficult to produce a solid acoustic timber flooring system in a 40mm space, when standard installations of 19mm thick floorboards are nailed to 19mm thick battens. 50-55mm of Floor Height is required to allow for either sheet rubber and plywood or an acoustic batten system installations - though some savings can be achieved by using a 10mm recycled floor on plywood solution.
   
   
4. Flanking - all one needs to do is to separate the floor and battens from the skirting and side walls. The problem is akin to holding a cup against a wall to hear what's on the other side.

Technology advances

Solid timber floors are already being laid using a variety of ingenious systems to improve acoustic ratings - such as abs6619 from Innovative Acoustic Solutions. There are now a number of good quality insulation products that are evolving and reducing in thickness (such as Quiet Step and the Regupol range of acoustic underlays). Combined with modern batten systems and the use of plywood they effectively allow solid timber floors to be installed so that they too float (both on concrete slabs or bearers) without compromising the structural integrity required by solid timber floors.

These systems do however come with an increased price tag, which will become the norm as people focus more on acoustic standards. The consumer is demanding a higher quality finish today than ten years ago - across the board and they are also prepared to pay for it. As with everything, if done right the first time, quality products will do the job and last the life of the building.

What also makes sense

1. Systems such as abs6619 (batten system) and ceiling cavities are not that expensive, are practical and have design advantages;
   
   
2. Most foam underlays do not pass the crushability test and do not offer long term acoustic solutions;
   
   
3. Timber floors can be quiet, very quiet if designed correctly!
   
   

Species	Colour	Hardness Rating	Durability Rating	Strength Group
Alpine Ash #	Light straw	5	4	SD4
Mountain Ash #	Light straw	4.9	4	SD3
Blackbutt	Pale yellowish brown	9.2	2	SD2
Box - Grey	Dark browns & reds	13.1	1	SD1
Brush Box	Pinkish grey / reds / browns	9.1	3	SD3
Ironbark - Grey	Dark browns & reds	16.3	1	SD1
Ironbark - Red	Dark reds	14.0	1	SD3
Kauri - N.Z.	Pale pink / reddish brown	3.3	4	SD8
Karri -W.A.	Pink / dark reddish brown	9.0	3	SD2
Mahogany - Red	Dark red	12.0	1	SD3
Messmate	Yellowish to greyish brown	7.1	3	SD3
Pines - Baltic	White / pale yellow	2.5	4	SD8
Pines - Cypress	Pale/dark yellow	6.6	4	SD6
Spotted Gum	Pale to dark browns	11.0	2	SD2
Sydney Blue Gum	Dark pink to red brown	9.0	3	SD3
Tallowwood	Yellowish brown / olive tinge	8.6	1	SD2
Turpentine	Dark pink to reddish brown	12.0	1	SD3
# These Ash varieties are collectively and commonly referred to as Victorian Ash. Tasmanian Oak is a combination of these and other distinctive ash varieties found in Tasmania. ## When it comes to structural beams and posts, strength, toughness, elasticity, shrinkage, weight, stability, lyctid borer susceptibility, edge splintering all need to be taken into account. Further details are available on the internet. ### Ironwood's feature beams and posts are old timbers that have usually been modified in their previous fitting. We therefore do not provide ratings on these timbers as they are sold purely for aesthetic purposes.

Our warehouse and display rooms are conveniently located in Rozelle (near the ANZAC Bridge). Come in and visit us, we are open Mon-Fri 7:30 a.m. - 5:00 p.m. and Saturday 9:00 a.m. - 3:00 p.m