Salt Damp Free Inspection and Quote

Salt damp in your home isn’t something to fear or shy away from. At Tech-Dry SA we offer treatment solutions that are suitable for all homes. Our work can be completed in stages to assist in keeping costs down.

Furthermore, getting on top of your salt damp and repairing the damage when you first notice it can help you to avoid expensive issues later on.

We completely understand, however, that it can be quite a confusing and scary time. That’s why, from your initial contact with us in the office to when you receive your quote on email, we try to make sure the process is pain-free and that you understand how best to treat and repair your home.

How can I make an appointment?

To make an appointment you can either call our office (on 81321166) or email us (by clicking here). A quick chat with Kim or Kate will determine if we can help (based on factors such as the age of home and location of the damp). If we can help, a suitable day and time is organised for your free inspection and quote. (We pride ourselves on being on time).

What happens during our Free Inspection and Quote?

Once on site our estimators, Neil or David will ask you to show them the areas of concern. They will determine if the issue is in fact Salt Damp (and not an issue caused by drainage, plumbing, backfill or another issue). And they will then assess things like the height of damp, how far spread the issue is and what damage (if any) has been caused to both your plasterwork and external walls.

They will measure up the affected walls and then discuss with you what they propose as a suitable course of action. They will discuss (and answer any questions) about the entire process. The treatment, the product we use, and the followup repairs that we will undertake inside and outside. An indication of price can also be given at this time.

During this time, they may also identify areas of your home that you will need to repair to prevent other damp issues such as leaking gutters, blocked downpipes or drainage issues.

Once they have finished they will draw up a diagram of the affected areas and put their recommendations into a written fixed price quote. This will be emailed to you approx 3 -5 business days after they have been on site.

Why Tech-Dry SA?

I think that is probably the most important question here – why trust us to undertake a free inspection and quote in your home.

Firstly, because of our experience. Both Neil and David have been inspecting and treating salt damp now for over 20 years. They both have a vast amount of experience assessing homes and heritage properties throughout all areas of South Australia. They are both specialists in Heritage. We can work with you to determine the best heritage outcome for your property.

Secondly, we have a Builders Licence, we are fully insured and all of our staff have Police Checks. We are members of the HIA and Master Builders Association of South Australia. We are also on the SA Government register for Heritage Approved Contractors.

Thirdly, it is entirely free (even if you don’t have salt damp). Our time and the advice given comes with no obligation, charge or hard sell. No dodgy tactics or incentives just honest advice based on our experience.

Most important, we will only quote you if you have salt damp!

Still, need some more information? Check out this video of the free inspection we did at the 1910 home of Lucy Cornes from She Shopped.

Restoration of Nic & Janet’s Stone Cottage – Adelaide.

Home restoration is never easy.  First, you need to get advice and then quotes, find a tradesman that is recommended and that will come on site as arranged.  Then you need to wade through the quotes, and check licences and seek feedback.  The process often takes a long time and can be very daunting.  It involves a lot of trust, understanding, and knowledge between the parties involved. As a homeowner I get it….  Our home is everything and I wouldn’t have just anyone repairing it.  

At Tech-Dry we see a lot of houses every day and as we often mention we feel very privileged to be trusted to be working inside and on the walls of our customers’ homes. We take the process seriously and want to ensure that our customers know that.  We like to make sure they understand what we are about to do every step of the way.

Nic and Janet’s restoration story

Nic and Janet were a prime example of this.  They knew they had Salt Damp in their old cottage, but a combination of factors had meant they hadn’t been able to look at the issue until now.  Add to this Janet had uncovered some of the stone underneath the crumbling external render and they wanted to see if the restoration of the original stone and façade was possible.  So, they gave us a call to see how we could help and to understand what was involved.  Finding someone they could trust to fix their home was very important to them.  

Not only were we able to help with the Salt Damp by installing a new barrier at the base of the wall to prevent further moisture and salts from rising into the wall.  We also had our team of qualified trades remove the damaged render, uncover the stone underneath and then lovingly restore the walls back to what they once were.   The process took many few months from the initial quote to the final restoration of the walls, but the result is more than worth it. The homeowners feel like they a new (old) cottage and it is now a perfect reflection of how it would have looked in the 1900’s and will last now for a long time to come. 

Why Tech-Dry SA?

This type of work is what we are experts at.  We understand the issues that these old walls face.  We understand the amount of salt in the old walls and exactly how important it is to get those salts out.  Our stonemasons are experts in matching mortar, mixing heritage approved lime mortars and ensuring the house looks like it once was. We spend a lot of time to ensure the job is done properly and will last.

As with all jobs, everyone was thrilled to be involved in Nic and Janet’s restoration project.  It was such a pleasure to see a 1900’s cottage being restored because we know what it looked like when we first saw it.  

By why not see for yourself and watch their story below.

Want us to come out and see how we can transform your home then contact us today?

Questions about Salt Damp

Every day we get asked the same Questions about Salt Damp.

Firstly, our customers want to understand what Salt Damp is? And they are also curious as to why Salt Damp is such a problem here in South Australia.
To answer these questions and more we have put together a refresher video (with some help from the lovely Lucy Cornes of She Shopped).

Salt Damp is the same as Rising Damp, but here in South Australia, our problem is amplified due to the high content of salt in our soil partly due to a large amount of land we cleared in our early settlement days.   As moisture from the ground underneath your wall is drawn up and into it so is the salt. And it is these salts that crystallise in the surface of the wall causing damage to your mortar, bricks and stone.

Some Signs to look for:

  If you are concerned that your home has salt damp, there are some signs that you can look for:

  • Wet patches that start at the base of your wall and gradually move upwards in a vertical fashion.
  • Skirting boards or plaster that is damp or rotting.
  • Plaster on your walls that is blistering and flaking awayOutside your home, you may notice that:
  • The mortar between your stone and bricks has disappeared.
  • The stones/ bricks are flaking, and dust falls from the wall when you brush it with your hands.
  • White salt stains that appear on your bricks/stones.

Why Tech-Dry SA?

Here at Tech-Dry, we have treated thousands of bungalows, cottages, villas and, for more than 30 years. We are passionate about preserving our state’s heritage and the homes built by our ancestors. Additionally, renovating and restoring homes is far more environmentally friendly than demolishing and starting anew.

We offer free onsite inspections in all areas.  Neil and David will come out and provide an honest and accurate assessment.  And they will quote you a complete solution including the treatment and the follow-up repairs.We employ a team of qualified and experienced technicians, plasterers and stonemasons.  This means we can make sure that your job is completed to exacting standards.

Tech-Dry SA is a proudly South Australian, family owned company. We are fully licenced and insured and we use an Australian-made water-based product.

Still have Questions about Salt Damp?

You can contact us here or call our office on 81321166 to organise an inspection at your home.

 

 

Rising Damp or Salt Damp?

Do I have Rising Damp or Salt Damp?

Are Rising Damp and Salt Damp different issues?

Can a house have Rising Damp but not Salt Damp?

I don’t have Rising Damp, but I have Salt Damp.  These are common questions or statements we hear from our customers. And understandably there is a great deal of confusion surrounding the two phrases. Hopefully, this article will help to clear that up a little.

So firstly, What is Rising Damp?

According to Wikipedia (Damp (structural) – Wikipedia. https://en.wikipedia.org/wiki/Rising_damp_in_buildings)
“In simple terms rising damp occurs when groundwater travels upwards through porous building materials such as brick, sandstone, or mortar, much in the same way that oil travels upwards through the wick of a lamp. The effect can easily be seen by simply placing a piece of porous brick, stone, or mortar in a shallow tray of water and observing how the water is absorbed into the porous material and is transported above the water line.”

And for the Wikipedia sceptics:
The publication “Salt Attack and Rising Damp” by David Young (2008) states that Rising Damp is “caused by capillary action (or suction) drawing water from the ground through the network of pores in a permeable masonry material”.

Ok, so now you ask – What is Salt Damp?

Salt Damp (as it is referred to in South Australia) is the SAME ISSUE.
So why do we call it something different?
No it’s not because we are from SA and we change names to suit us (yes I am referring to the Fritz / Devon debate) and no, we haven’t consumed too much of our famous Shiraz. On this occasion there is a valid reason.

South Australia suffers from extreme soil salinity because of considerable land clearing in our early settlement days. This has meant that we have close to ground level  water tables full of salt and very salty soils. In turn, this means that when groundwater travels upwards through our porous masonry, it carries with it large quantities of soluble salts. And it is these very salts that cause considerable internal and external damage to mortar, bricks, stone and plaster.

So therefore very early on the issue in SA became known as Salt Damp. Mostly because the damage caused by the salt in the masonry was far more significant in this state than in other states. In other areas of Australia, the UK and Europe their walls are affected by moisture and salt (Rising Damp & Salt Attack), but in South Australia, the decay in our walls happens more dramatically and to a higher degree. The salt content in our walls is considerably higher and the damage caused by Salt Attack greater.

Conclusion

So to conclude, whether you call it Rising Damp or Salt Damp then, either way, you are calling it the correct thing. There is no difference in the issue itself –  Salt Damp is just the term referred to by most South Australians.

However, one issue does remain, and that is you have a problem that needs to be repaired.   And to minimise the damage that occurs you are better to do this sooner rather than later. We would recommend that you will need to have it checked and repaired by a licenced and experienced professional.

Want us to come out for a free inspection; then either call us on 81321166 or click here to contact us. 

Case Study: Salt Damp Repair – Clarence Park

Case Study:  Salt Damp Repair Clarence Park

Location: Clarence Park

Type of Home: 1920’s Bungalow – Sandstone front, red brick to sides

Project Manager: Neil Williams

Issue: Severe damage to sandstone and bricks at base of the wall due to long-term exposure to salt damp.

Solution: Tech-Dry rebuilt some areas of wall before injecting a new damp proof barrier at the base of the walls.    The client then waited 6 months to allow time for trapped moisture and salts to evaporate to the surface.   Tech-Dry then repaired the front stonework and side brick walls of the home.

Details from Neil:

Marie asked us to inspect due to concerns about the condition of her walls.   The first thing I noticed was the damage that had occured to the sandstones on the front verandah and walls.  These  stones had been eaten away by the salts and some of these were almost completely gone.   On the side walls the mortar between the bricks had become crumbly and had eroded to the point that i could put my in between the bricks.  And this was happening up to 11 courses of bricks from the ground.   This is quite severe for salt damp.

The first thing I determined was that injection was not going to be possible until we had rebuilt some of the walls.    We proposed to the client therefore that we needed to rebuild sections of her wall, then inject a new Tech-Dry chemical damp proof barrier at the base of the wall.  The new barrier would stop any new moisture (and salts) from rising into the wall.  Once the barrier had been created we would need to wait 6 months.  This time allows for the walls above this barrier to “dry” before we can get our stonemasons back onsite to start the repairs.

Once the 6 months was complete our stonemasons returned onsite to work their magic.  They began the slow process of removing the salt affected pointing and replacing it with new lime mortar.  They also removed any of the affected sandstones and bricks and carefully choose their replacements.  This means the new stones will blend in with the existing stones in the wall.   Where necessary they also cut blocks of sandstone by hand to place into the wall so that they fit.   As a part of our overall repair service they also completely replaced the verandah floor as the previous slab had moved and cracked.

From the Client:

“I would like to pass on my appreciation of the magnificent job done by your staff, who I found to work together very well.  I am more than pleased with the work they did and I will certainly be more than happy to recommend Tech-Dry and your employees to anyone who is looking for damp proof work to be done.  Thanking you, Marie”.

Ready to get a quote for your home then click here to contact us to organise a suitable time. 

VLOG: Tech-Dry SA Heritage Interview

Heritage in South Australia
Tech-Dry SA and the National Trust of South Australia

Recently our General Manager, Neil Williams sat down with Dr Darren Peacock, Chief Executive Officer of the National Trust of South Australia to discuss all things Heritage.

Looking for some more information on how we can help you heritage property then check out our page on Heritage Buildings or click here to contact us.

Slab Edge Dampness – It’s not Salt Damp! (but it is still a significant problem)

Slab Edge Dampness

Disclaimer:  Please note this is general advice only.  The issue of Slab Edge Dampness is not Salt Damp and therefore we are not experts on this issue. We recommend involving a building inspector or engineer to assist in identifying and rectifying this problem.

Symptoms of Slab Edge Dampness

Are you experiencing any of the following?  

  • A persistently damp concrete slab
  • A damp line appearing on the surface of your concrete slab
  • White, furry, salts appearing on the edge of your concrete
  • Render on your foundation blistering and bubbling and falling off
  • Bad odours (due to dampness in floor coverings such as thick carpets)
  • Rusting and Corrosion of Metals around the slab edge.These symptoms could be an indication that your property has an issue with Slab Edge Dampness.  Slab Edge Dampness can also be referred to as Efflorescence or Slab Edge Wetness.   All of which are a problem that is becoming more prevalent in properties throughout SA.

(And despite the common confusion – it is not Salt Damp, and therefore we are unfortunately unable to assist or treat by the usual means of treating Salt Damp).

So what causes it?

Slab edge dampness can be a result of a variety of factors such as:

  • poor quality concrete,
  • incorrect slab construction and drying,
  • poor drainage,
  • inadequate and lack of a waterproof membrane,
  • weather events,
  • post-construction landscaping or paving.Most of these factors allow the slab edge to become affected by contact with water and the salt contained within it. It is this that can cause the concrete to erode.

It can be difficult to determine what has been the exact cause of the problem and that is why we always recommend engaging an expert to undertake a thorough investigation.

Why Salts?

Salts are damaging when in contact with masonry or concrete.   And water-soluble salts can be found in many sources, most commonly groundwater.   When this groundwater is in direct contact with foundations, slabs, or retaining walls the moisture and salts pass through the masonry at a rate dependent on their porosity.  As moisture passes through the slab and evaporates, salts are left behind and crystallise below or on the surface. This creates a build-up of white powdery fluff known as efflorescence.

It can take years for any evidence of efflorescence from groundwater to appear, or it can take very little time at all.

Another potential source is that salts can exist in the mixing water that was used in the mortar, render or concrete.   Or the concrete was exposed directly to the elements and moisture was allowed to absorb before construction.

Effect of Salts?

These salts if left unchecked will begin to affect the overall appearance of the masonry/concrete. Firstly the salts themselves look unsightly.

Secondly, the efflorescence will harden and will slowly begin to erode away the affected surface.    This will crumble, pit and potentially expose the aggregate.

What can I do about this?

Yes, we keep banging on about this, but we recommend, firstly engaging a licenced and experienced consultant to assist you with identifying the cause of your issue and then offering possible solutions to help rectify or prevent further damage.

Some of the options they may suggest include:

  • Increasing drainage around the perimeter of your slab.
  • Correct surface water flow when landscaping
  • Digging down and installing a waterproof barrier between the edge of the slab and the ground below.
  • Sealing the external perimeter of the slab.
  • Fixing any guttering, storm-water or down-pipe issues.Ultimately, you will need to remove any sources of excess water. And create a barrier between any groundwater and the edges of your concrete slab.

Need more information then follow this link to another data sheet from the CCCA.  

Your Damp House Winter Checklist

Last winter in Adelaide it rained.  I mean it really rained.  The storms were quick and ferocious.   Now, our house has small leaks that we know about and thanks to lots of gum trees, gutters that overflow.  Its all pretty typical for an older house and a busy family with other priorities.  What do they say about builders that never get around to fixing their own home? Well, damp specialists never getting around to fixing their own damp house. 

But last winter something else happened that caused my husband and I to sit back and decide it was time to do something about it.     It was a particularly heavy rain event and we were having some friends over for dinner.  Their son came out of our toilet and complained that hot water had been falling on his head.   We both rushed to look and discovered that water was leaking from our roof through the ceiling light onto the floor.  We made the area safe at the time but decided that night it was time to waterproof our damp house.

 Luckily as damp specialists we knew where to start but we have prepared this checklist for you to check your home this winter and avoid any nasty surprises. 

WINTER MAINTENANCE CHECKLIST

  1. Clean out and check your gutters

gutter blocked with leavesNow that the autumn leaves have stopped falling it is time to check and clean out your gutters.   Empty them of leaves, mud and debris and hose clean where possible.

Cleaning your gutters means that rain can drain away easily and it won’t overflow as quickly.   This prevents water damage to your eaves, inside your roof or below on your pavers and foundations.

Check your gutters for rust spots, holes and breaks also and fix and/or replace if required.

  1. Check your down pipes

Whilst you are up on the ladder it is a great chance to check all your homes down pipes as well.    Are they connected properly?  Are there any holes or breaks?   Do they drain away to storm water at the base.

By ensuring that your down pipes are attached properly you prevent incidences of what is commonly called falling damp.  Continual moisture against your masonry from a leaking pipe can cause rising damp type symptoms such as salt stains, blistering paint, plaster and erosion of mortar.   In extreme cases you can also get mould.

Fix any issues if required – you may need to call a specialist for this.

  1. Check your roof

And finally, check your roof for any cracked, broken or missing roof tiles.   Ensure that the flashing is in place and that ridge tiles are secure and unbroken.

If you have any damp patches on your ceilings that could be a sign that you have a cracked tile, ridge or a leak somewhere in your roof.  It is worth at this point calling in a roof expert to thoroughly check over the area and determine where the leak is occurring.

  1. Check drainage around your home

Are there any areas that water pools up against your home?  Or do you find water seeping in during heavy rain?

If so now might be the time to improve the drainage around your home.  You may need to investigate installing a series of Ag drains to direct water away from the area of concern.

Do you have drains blocked with debris?    Clean them out to allow water to drain away easily.

  1. Rain Water Tank

Is your rain water tank securely attached?  Do you know where it overflows?   Does it flow down and away from your house?

Check all connections for your rain water tank.  Are they free of debris and in good working order and is the overflow working as it should.  If your tank is full it could be worth using some of that water now or draining some of the water in preparation for heavy rains.

  1. Prune your trees

It is worth pruning any branches that are dead or overhanging the house or power lines now.  Better to do it now than have heavy branches fall on your roof in the middle of a storm.

  1. Chimney

If you have a working chimney make sure it is cleaned out prior to winter. Every couple of years get it inspected by a professional to prevent safety issues and fire hazards.

These maintenance steps will obviously not protect you from a severe thunderstorm event or from flooding but it may help to prevent a damp house this year.      To help you take measures to protect your family and pets during severe storms then click on this link to the SES website for further information.  

Cost of Fixing Salt Damp

WHAT IS THE COST OF FIXING SALT DAMP?  

We understand that there is a lot of confusion and misinformation regarding the cost of fixing salt damp.   And whilst a free inspection and quote is helpful we get that you are researching firstly to determine if it’s within your budget.    Or maybe a building inspector has just alerted you to an issue in a house you are considering buying and you need to know what it will cost to fix.

Our aim with this article is to provide you with up-to-date honest and reliable information to help you budget for your project and understand the hidden costs involved.

Please remember that this is a guide only.  It is not a quote and prices will vary at your property. 

Firstly there a few things to consider:

  1. Is your problem definitely Salt Damp?
    It is worth reading our checklist first. Click here to read. Often the issue relates to another form of damp, condensation, mould or musty smells and so therefore these costs won’t apply.
  2. Will maintenance fix the Salt Damp?  Are there other tasks around the home that will fix the issue?  For e.g. Could you lower the pavers and expose the existing damp proof course?   Or could you improve the issue with increased drainage?
  1. Will you be removing these walls in the next 1 -3 years?
  2. And lastly how badly affected are the walls?  In some rare occasions it may be impossible to inject a wall for structural reasons and it will therefore need to be rebuilt first.

COST OF FIXING SALT DAMP?

Now let’s get down to the reason you are still reading… what is the cost of fixing Salt Damp?     Our advice relates to the injection of a waterproof cream barrier to the base of your walls to prevent the rise of moisture and salts.

The cost of injection does vary significantly from property to property and is dependent on things such as:

  • Thickness of walls

    Treatment with cream is done from one side of the wall only regardless of the situation.  The price increases as the thickness of the wall increases.  A single brick wall is charged a lot less than a double brick / double brick with cavity.
    Price Guide:
    Single Brick                                                                  $70 – $95 per lineal metre
    Double Brick/Block                                                    $85 – $105 per lineal metre

  • Fabric of the walls

    There are many types of masonry and each has its own issues.   Limestone is more porous and may have greater damage but bluestone is harder to drill into and requires more product.
    Price Guide:
    Brick:                                                                                as above
    Block:                                                                               as above
    Stone below 450mm thickness:                                 $120 – $150 per lineal metre
    Stone above 450mm thickness:                                 $150 – $200 per lineal metre

  • Damage to the wall

    Treatment only stops further moisture and salt from rising into the wall.    After the initial treatment  follow-up internal and external repairs are required.  e.g. removing and replacing damaged plastering, removing and replacing damaged render, replacing missing mortar or badly affected stones.   These costs should be considered in your overall budget and you should request a quotation for these at the time of inspection.  The amount you pay for these repairs will be determined by the client and is dependant on how far you wish to take the repairs.  Some people only wish to repair damaged areas others wish to restore the home fully.    Dependent on the damage too some tasks will take a couple of days others will take a few weeks.

  • Height of the problem

    Salt Damp normally does not rise any higher than 1 metre.   However, sometimes the issue has been left for a long time and the height of the problem has risen beyond what is considered normal.   The repairs of this could therefore cost more.

  • Number of metres
    You may find also the more metres you do the less it will cost.     Also a minimum charge to cover setup may apply.

ADDITIONAL COSTS:

As with any building project there are additional costs which may be relevant in your situation and these should therefore by factored in.   These can include (but are not limited to).  It is important to ask about these at the time of your onsite inspection.
– Removing and replacing power points, data points and telephone points.
– Removal , refitting and/or replacement of skirting boards and tiles
– Temporary relocation of air-conditioning unit
– Painting / flushing joints
– Generator Hire
– Rubble / Waste removal

There is a lot to consider yes.   But by using a fully licenced and trusted professional the fear and uncertainty regarding the treatment and repairs should be less.       An onsite inspection, fixed price quotation and discussion with professionals should give you all the information you need for your project.

Ready to get a quote? – click here to request a call to organise a time. 

Tips on how to choose a builder and finance your renovation

Many people approach us to fix their salt damp at the beginning of a larger renovation.  We often hear how stressful the process of renovating is and how much confusion exists on financing it.   To help alleviate some of the stress we have asked the experts at MacNab Finance for their tips and tricks for financing and budgeting for a renovation.  They have also shared their handy checklist of questions to ask a potential builder before commencing your renovation.

Ask the Expert: Tips on how to finance your renovation and choose the perfect builder.
MacNab Finance


Finance Tips for Renovations 

Building or renovating is a great way to achieve the house you desire. You have the freedom to add quality craftsmanship and the design features that you and your family will value. Creative projects like these are both exciting and stressful.  Not only do you need the right loan features to save financially and have greater control of your project, you need the right advice on how the loan is to be considered by your lender.  For example: building/construction loans aren’t generally available for renovations unless they are significantly structural and with a fixed price build contract (for example adding another level or extension to your existing home). For a kitchen or bathroom renovation you would typically use your existing equity.

When it comes to choosing finance to build or renovate your new home, there are a number of associated costs to consider. You will need to factor in stamp duty (on the mortgages), legal costs, insurance, surveys and searches, inspections, council rates. Other costs you may incur are rent and moving costs (if you have to rent while your new home is being built) and landscaping expenses after the building is complete if they were not included in your contract.  With so much to think about, it’s important to have the correct loan to suit your project. Be sure to engage the professional services of a finance specialist like ourselves before entering into any contract with a builder

Choosing a Builder?

Choosing a builder who is right for your project can be the difference between a massive headache and an enjoyable, hassle-free project.
It’s important to know what to ask your builder. The following checklist will provide a good starting point. Don’t be scared to ask these questions. Remember – it is always better to ask upfront than to find out critical information when it’s too late.

  •  Visit the websites of the Housing Industry Association or the Master Builders Association for builders in your area, then make a list of potential builders.
  • Check each builder’s website for images and photos of recent work and look for testimonies of other people who have recently used their services.
  • Ask these questions of each builder so you can compare quality and experience, allowing you to see how easy it is going to be working with them.
  • Are you able to provide me with your builder’s registration and licence if we proceed with you? You can also check this online – click here for link
  • What evidence can you provide that will show you are financially sound and can complete my project?
  • Are you currently insured?
  • What are your professional memberships and registrations? (HIA/MBA/other?)
  • How many years have you been in the industry?
  • What experience do you have with renovations/new builds?
  • Can we speak with some of your most recent clients?
  • Do you provide a written itemised quotation clearly outlining what is included or excluded in the price?
  • Are there any hidden or extra costs that may be charged?
  • What are your standard features and what will cost me more?

For more information or to discuss finance options further then give Linda and Mark MacNab a call on 83576806

macnab finance

 

 

 

 

MacNab Finance
21 Benjamin Street St Marys SA
08 8357 6806
info@macnab.com.au