News and Updates

How tall is a Power Pole?

Preschem has been receiving a few questions via email asking, “How tall is a Power Pole?” It’s an interesting question. The answer is based on many variables, so has no one specific answer. Lets explain and get to the bottom of this.

Firstly, we are only going to talk about timber poles. This discussion is not about concrete or steel/concrete “Stobie” poles used in south Australia and the N\northern Territory.

How tall is a Power Pole?

Power Poles in Australia have a minimum height requirement, which happens to be 4.5 m above ground. In  some situations this requirement is greater due to the need to clear terrain, or the type of pole. In such circumstances, the pole can be 5.5 m or even 6 m in height.

But of course there is also the below ground component to the pole. Usually the Pole is to be placed in a hole that’s a minimum of 2 m deep. But this can be up to 3 m depending on the height of the pole, wind loadings  and the soil type.

Therefore the total butt to pole top height ranges from 6.5 m to 9 m. Though the 9 m timber poles are very rare, as it’s difficult or near impossible to source logs that long. The vast majority will be within the 6.5 m to 8 m range.

So what type of pole would require additional height?

Power poles are categorised into 3 general classes depending on the environment that they’re in. These are:

  1. Distribution – which supplies homes or businesses in the street with mains 240 V power
  2. Transmission – is the electricity backbone carrying high voltages of at least 11kVA. They are usually taller than distribution poles.
  3. Hybrid transmission and distribution. Carries both high voltage transmission and mains voltage distribution lines. You will note that they usually have transformers at regular intervals mounted on the poles where they need to feed power from the transmission lines into the distribution lines.

So how do you determine the height of a specific pole in the field?

If it’s a sunny day, then it’s quite easy to do safely. We measure it’s shadow. Here are the steps:

  1. Find a stick or straight edge 1 m long. If can be another length but as long as that length is known. 1 m is easy to do the maths.
  2. Place that stick vertically and measure it’s shadow. Write that value down.
  3. Measure the shadow of the pole.
  4. Calculate the shadow height to shadow ratio of the stick and then divide

Eg. Lets say the 1 m stick is throwing a shadow of 0.6 m. The height to shadow ratio is therefore:


We measure the shadow of the pole as being 3.0 m. Now we multiply it by the ratio we calculated to find the height of the pole.

3.0 x 1.67 = 5 m

It won’t be to the nearest millimetre, but it will be surprisingly accurate provided you don’t leave it too long between measuring the stick and pole shadow. Remember the sun will shift in the sky and alter the length of the shadow.


Deck Preparation for Staining and Oiling

Sooner than you think, the warm weather of spring and summer will return. Everyone will be looking forward to entertaining on, or simply enjoying their timber deck. So that means it’s time to start planning the deck preparation as part of its maintenance. After all we all want our decks liking like it did when it was first installed all those years ago.

But before you start oiling you have to prepare the deck to get a great result. This means removing the dirt, grime and the UV weathering that has built up. The best means to do that is to use Preschem’s Grey Deck Cleaner. This is a mild oxalic acid based cleaner that restores your deck to the “as new” colour. This doesn’t take long and you’ll need an hour or so. And I’ll let you in on a little secret. When I did my deck at home last year, it had been 2 years since I last done it. So I’m going to take you through this process step by step, with photos along the way.

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Why Timber Changes Colour

Exposure to Weather | Sapstain Mould | Bluestain Mould | Iron Staining

Earlier this month (May 2016), Preschem was asked to give a presentation on why timber changes colour at the Victorian Woodworkers Association. This got us thinking that this topic would make a great general knowledge post. After all, this will assist with some of those decisions on what to do when building something out of wood.

Why does timber change colour?

  1. Exposure to weather, including UV and rain
  2. Staining due to natural or introduced causes
  3. Chemical changes within the wood resins, or “extractives”
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Timber Properties and Decay. Part II


Brown Rot

White rot with mycelium

The following article was published by the Professional Pest Manager magazine in their August-September 2014 edition. It was the followup article/conclusion to the June-July 2014 edition.


The prevention of wood rot falls into 2 categories, moisture barriers and timber preservatives. Moisture barriers can be any membrane like material that physically limits or stops moisture ingress. The most common forms of barriers are surface coatings such as paints, varnishes or specialised synthetic membranes. While these are usually brilliant in preventing moisture uptake, they do have a potential downside. If they begin to fail, the moisture can become trapped behind the barrier.

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Timber Properties and Decay

Timber Properties and Decay | Timber decay around homes

This article first appeared in the Professional Pest Manager Magazine June/July edition (Subscription only). Please note it was written with pest controllers in mind.

Timber decay around homes and properties is generally poorly understood by the general public. Pest controllers will inevitably come across decay that has been miss-diagnosed by the property owner as termite or borer attack. Thankfully, due to the internet, this is less of an issue now than it used to be, but sometimes a little information (from the internet) is a potential recipe for disaster. There is also no doubt that during the inspection process for a potential insect or rodent infestation, that the pest controller will come across decay. There would be hardly a premises in Australia that doesn’t contain it in some shape or form.

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Preschem’s Commitment to Innovation

Commitment to Innovation | Product Research and Development


Preschem’s range of industrial power pole wood preservatives and DIY/Architectural finishes are mostly unique formulations. They are unique due to our commitment to innovation. To achieve this level of innovation and proven product reliability is not an easy undertaking. Behind the scenes, it takes a lot of hard work in terms of Research and Development. R&D can also be a lengthy process, as to prove the formulation works, it can take up to 10 years of field trials and analysis of those trials. In addition, all timber preservatives have to be registered under government legislation, so to get a new product up and over the line with a complete data pack is also very expensive. I have discussed the registration process in this previous post.

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Best Decking Oil Results

Deck Preparation before Oiling | Weathering timber

Previously, I have discussed the problems that people commonly have when they apply Aussie Clear to Merbau decking. As I stated in that post, to achieve the best results, deck preparation before oiling is essential:

  • once the deck has been installed, allow 6-8 weeks for it to weather
  • weathering of decks allows the resins, tannins, waxes and natural pigments (all called extractives) to bleed out
  • the weathering process also starts to open up the timber fibres

All of the points above mean you will be able to apply more Aussie Clear to the timber. Your first application of decking oil will last much longer.

All this theory is very good, but where is the proof in the pudding?

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Preventing Balcony Collapse

Preventing Balcony Collapse | Balcony Maintenance

The Channel Nine Today Show reported that there had been 4 balcony collapses over last weekend, one of which resulted in the death of a man. Earlier in February this year, there was another balcony collapse on the Central NSW coast which claimed the life of a baby that also put his mother into hospital with a suspected broken back. These tragedies are usually result of either poor workmanship or from timber decay.

How do you prevent balcony collapse?

  1. Regularly inspect the timber structure for signs of decay.
  2. If decay is present, determine if its superficial or more substantial.
  3. If superficial, apply a presevative system to kill and prevent further rot.
  4. If you are not sure how to diagnose the extent of the problem or it is substantial, call in a registered builder to repair or replace the weakened structural timbers.
  5. Make a diary note to inspect it again in 12 months time.
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Registered vs Unregistered Pesticides

Registration of Pesticides | APVMA | AgVet Legislation

I receive a lot of technical enquiries from the public about how to control timber decay. Mostly, it’s from someone have needs to repair an issue they have or wish to prevent it from occurring. There is one thing that crops up occasionally which is a concern; they sometimes mention they’ve heard of, or been recommended a product by someone. When asked the products name, I’ve never heard of it. A quick check on the APVMA’s Pubcris database often shows that it’s not a registered product! All products that are designed to kill another living thing are classified as pesticides under the AgVet legislation. So why is the registration of pesticides so important?

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Aussie Clear – Decking oil for all hardwood timber

Decking Oil for all hardwood timber

AUSSIE CLEAR and AUSSIE CLEAR LIGHT are Preschem’s range of decking oil for all hardwood timber. The philosophy behind this is that most hardwood timbers available in Australia are very similar in their properties. Even if their natural appearance are different. Thus a simple range of timber finishes will fit the bill.

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