Chemical Delignification

What is Chemical Delignification Classified as and Why?

Chemical delignification and how it should be classified. Over the last couple of years, there has been a lot of misunderstanding surrounding chemical delignification when there is really a simple answer to the question what should chemical delignification be classed as? In AS4349 it can appear in two versions it can be ruled in AS4349.1 as material deterioration or AS4349.3 as a timber pest, but NOT 4349.3 timber pest when conducting a pre-purchase inspection, here is how it all works below, broken down as best we can so as everyone has a clearer picture of what chemical delignification is, its cause and effects and the way it is required to be reported in your pre-purchase inspection.

Is Chemical Delignification A Major Defect?

MAJOR DEFECT – A defect of sufficient magnitude (adequate) when rectification has to be carried out in order to avoid unsafe conditions, loss of utility or further deterioration of the property.

Chemical Delignification happens when the salts and other chemicals are leached deep into the lignin of the timber and physically break it down when the moisture dries up and the salt crystalises. The moisture is drawn into the timber through the tiles above from their contact points, (mainly the top of the batten and back lugs)

Chemical delignification can first be identified as off yellow type staining on the timber battens this is at a stage that maintenance could still be considered an option as the actual crystallisation and breakdown of the lignin has not yet begun, but once the timber shows signs of ‘fluff’ or ‘hairy timber’ as it has been referred to commonly in the past the breakdown of the lignin has begun and this is when the timber has reached the stage of sufficient magnitude where the strength of the member/element has been reduced.

There are some building inspectors and even structural engineers that are using callipers to measure the exterior dimensions of the battens after scraping back the ‘fluff’ insistent on the fact that there is still a solid piece of timber behind this ‘fluff’. To this first, let me say this ‘fluff’ they so lovingly refer to is the lignin from the timber (The Main Component In The Timber Retaining Its Structural Integrity) the ‘fluff’ is scraped back and there is a seemingly solid piece of timber behind that ‘fluff’, but they are working on the assumption that the delignification is a surface defect, this is because some of them have not taken the time to actually learn about chemical delignification, (Although if you are inspecting homes and people are putting their trust in you when purchasing potentially their biggest ever asset, you would think it would be a priority). While some inspectors seem to have a clear understanding of what delignification is, its cause and effects, yet they not only chose to ignore it, but they are also choosing to try and boycott it all together, while they agree it is a major defect, they have chosen a different angle, they have chosen to say that the roof frame is not a structural element.

If we are to look at page 30 table F1 of AS4349.1 material deterioration: It states severe delignification such that the strength of the member has been reduced. If a home is 40-50 or 60 years old, we need to remember this delignification in the battens hasn’t started 40-50 or even 60 years ago, for the delignification process to begin there first had to be the 30-40 or even 50 years before the tiles naturally break down enough for the tiles to become porous enough to retain significant amounts of moisture for long periods, then for the moisture to combine with the salts and other airborne chemicals that have landed on the roof over the years, together with the natural sodium chloride found in the clay roofing tiles themselves to be able to be literally sucked out by the timber below and drawn through the timbers veins, or more commonly referred to as lignin. Lignin is “A structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism, commonly referred to as the glue that binds the timber, it provides the timber with the tensile strength that is essential to provide the structural integrity required to support a tiled roof.

When conducting a pre-purchase inspection under the guidelines of AS4349.1 certain facts need to be taken into account.

Undeniable fact: – Once lignin has begun to break down, the strength of the member is reduced.

                                Once chemical delignification has started to take effect it will continue to deteriorate.

                                Roof tile battens are part of the roof frame and must satisfy NCC P2.1.1 structural stability.

These three simple things alone tell you that chemical delignification is a major structural defect and once it is at the stage where the lignin has begun to break down it is no longer maintenance and can only be classed as a major structural defect due to the fact it is going to continue to deteriorate the tensile strength of a structural element of the property. Because chemical delignification is not being reported correctly as per the AS4349.1 these inspectors are leaving their clients without the option to enforce the REIWA clause for structural defects to be rectified prior to settlement.

On the day of inspection: – On the day of the inspection when conducted under AS4349.1, the scope as described is.

2.3.1 General The inspection shall comprise a visual assessment of the property to identify major defects and to form an opinion regarding the general condition of the property at the time of inspection.

As we have already discussed above, the definition of a major defect when conducting an inspection under AS4349.1 is to include further deterioration to the property if an element already contains a defect. We have also discussed above that when chemical delignification is identified in a roof, at what stage it is to be identified as maintenance and when it can be identified as a major defect.

If a roof framing element is seen to have the tell-tale yellowish staining that we know is the infant stages of chemical delignification, this is the early stages where it has not quite got to the stage that the lignin has begun to break down and the tensile strength of the batten has not yet been compromised. This would be classed as a maintenance item, and you would make your client aware of the consequences of not addressing the issue.

However, should the roof framing timbers get to the point where they have started to break down and the yellowish stain is now actually ‘fluff’ or ‘hairy timber’, which is actually lignin that has been broken down and forced out of the timber reducing the tensile strength, it is at that point to be referred to as a major structural defect. Again, it is a visual assessment on the day of inspection that is to be made. Too many of these inspectors are using callipers to measure timber, or screwdrivers to poke at it, scrapers to scrape it back and attempt to make assessments of how bad the timber has been affected. Their visual assessment alone is what actually tells them that the strength of the member has been reduced. This is exactly what they have been instructed to report on, I will again refer to page 30 table F1 of AS4349.1 and chemical delignification without rectification is going to continue to deteriorate.

Why inspectors are doing ‘invasive’ inspections or having structural engineers called in to take measurements of the external wall of a defect that is within the timber element itself is a testament to the fact that all of these inspectors and structural engineers need to be further educated on the subject. Page 5 AS4349.1 – is implicit in this Standard that the inspection includes a subjective appraisal by an inspector competent to assess the condition of residential buildings.

Can Chemical Delignification Be Classed As Maintenance?

MAINTENANCE – description A system or component requiring maintenance that appears to be functioning as intended, but would benefit from minor repair, service, maintenance or improvement at this time. This may include patching, painting, cleaning, or in some instances a system service by an appropriate specialist.

Maintenance is a preventative measure, an act conducted to prevent an element from obtaining a defect. Once a defect is already established it is no longer a maintenance issue, it then becomes a matter of rectification.

In the case of chemical delignification maintenance would have been keeping the roofing tiles maintained and in good order, over the years terracotta roof tiles will slowly break down and lose their protective glaze, when this happens general maintenance is required to ensure the deterioration of the tiles if kept to a minimum, this is generally done in via a soft wash technique where a chemical agent is used to break down any lichen or other moulds and then a new protective clear glaze applied to preserve the tiles and therefore prevent the onset of chemical delignification.

Chemical delignification is caused by chemicals, namely salt/sodium and other chemicals being leached from the tiles above once they have lost their protective glaze and become porous, this process is further accelerated the more the tile breaks down and once the delignification takes hold maintenance is no longer a valid option as you have the breakdown of two vital elements of your home your roof tiles (roof cover) and your roof battens (roof frame) sometimes even rafters are affected. Because chemical delignification is not being reported on correctly as per the AS4349.1 these inspectors are leaving their clients without the option to enforce the REIWA clause for structural defects to be rectified prior to settlement.  

Is Chemical Delignification a Timber Pest?

Timber Pest:- This is a slightly more complex one to deal with is chemical delignification a timber pest, the answer is actually yes, chemical delignification is a timber pest when conducting an inspection under AS4349.3 BUT it is not recognised in AS4349.3 when conducting a pre-purchase pest inspection, it is instead reported on as material deterioration under AS4349.1 which is the Australian standards used when conducting a pre-purchase building inspection.

So as an inspector conducting a pre-purchase pest inspection AS4349.3 chemical delignification is not recognised, however as an inspector conducting a general pest inspection under AS4349.3 you are to report on chemical delignification as a structural timber pest.

A lot of inspectors are unaware of this and chose to report on chemical delignification as a timber pest when conducting a combined structural building and timber pest inspection. Unfortunately, because it is not reported on the correct report, nor is it classified properly as per the AS4349.1 these inspectors are leaving their clients without the option to enforce the REIWA clause for structural defects to be rectified prior to settlement. 

Unseasoned Timbers Strengthening Over Time In The Roof?

Unseasoned timbers: – Whether timbers are installed as seasoned or unseasoned the fact remains the same, the lignin is being attacked and the strength of the member is being reduced as a result. Once the strength of a member is compromised it makes no difference how it was installed, it is going to continue to deteriorate and therefore is a major structural defect as noted above.

Another interesting fact, looking at one blog in particular from home integrity, it has a video of them scaping back the batten and showing what seems to be a solid bit of timber behind, this is something we have already covered and the pictures provided will discount that theory. But this blog is again a testament to the lack of knowledge or study that has actually gone into this by these inspectors who are leading the charge to have it ruled out.

The blog states ‘Tile battens are installed as unseasoned timber. Any reduction in strength due to the reduced cross-section is more than offset by the increase in strength over time as the originally unseasoned battens have dried in service’. Ok if this is true then what this inspector should actually be saying is that because these tile battens were installed as unseasoned timber and over time have dried in service makes them considerably more susceptible to attack from chemical delignification. You see the fact that this timber was installed as green timber as it dries out it will be trying to replenish that source of moisture and the dryer the timber gets the more moisture it will absorb. When that timber is absorbing moisture from the only source that it can, the terracotta/clay tile above, then it is actually going to increase the introduction of chemicals being leached in from the clay. Essentially as the timber is becoming seasoned on the roof as it is stated, it is actually concurrently setting itself up to be broken down by drawing in the outside pollutants and salt from the tiles above.

That is not to say a seasoned timber installed is any better or worse, any dry timber is going to draw moisture from external sources and the dryer the timber the more moisture it will absorb, therefore the more chemicals/salts it will absorb. If timber is being seasoned while it is already installed, it makes sense that that timber would be attempting to draw moisture to replace what is being lost and this could definitely explain why we see such a much more aggressive form of deterioration in some roof tiles where they are in contact with the timber, as the timber is curing/drying it would be attempting to really pull water from any source, therefore breaking down the tile above to reach the moisture trapped higher in the tile. The already seasoned timber has already been through this process and therefore is not searching for the moisture to replace, although once the moisture reaches the seasoned timber it will then start to draw it through, this means although it is drawing the moisture through the tile itself, it hasn’t been so aggressive in its search for the water and will break down the tile at a slower rate than the timber that was installed as unseasoned.

Inspectors Incompetence and Chemical Delignificaion

Inspectors’ incompetence: –When it comes to chemical delignification the level of incompetence in inspections throughout the industry is actually quite scary. We have some inspectors telling customers that the chemical that is breaking down the timber is H20, water, and calling it chemical delignification is just a fancy way of saying it.

We have other inspectors classing it under the timber pest section of their reports which would be fine if you were not conducting a pre-purchase inspection, AS4349.3 does not recognise it under this section. AS4349.1 picks it up as material deterioration.

There are others that recognise it as it is, a major defect, however, they have chosen to say that the roof tile battens are a part of the roof cover and not the roof frame.

Why: – With all these different characterisations of the same defect, yet all having the same outcome, (not classed as a structural defect), it beggars the question, why, on something that is so straightforward, literally the easiest defect to diagnose, why are there so many wrong classifications for the same defect? Why are all these building inspectors that are hired by consumers when making the biggest purchase of their lives, why are these TRUSTED inspectors trying their hardest to work out a way around classing a defect as it should be classed?

One thing I have noticed is that all these inspectors have one thing in common, they all rely on selling agents for referrals and there is one thing I know sellers’ agents hate, is settlement being held up due to a structural defect, or even worse, their commission taking a hit because a defect needs rectification prior to settlement, or worst-case scenario the sale falls through all together due to a structural defect.

What Are We Doing About Chemical Delignification In Perth?

Chemical Delignification in Perth: – When it comes to chemical delignification in Perth, I have decided to dig my heels in and fight back, over the past few years I have seen more and more that people are getting screwed over by their inspectors and they worst thing is they actually think these inspectors are great people that have done a great job for them. Yet they have been left with Major structural defects that they are having to get sorted after their settlement has already been decided, leaving them out of pocket instead of being able to activate the REIWA annexure to have it rectified as part of the sale. No more Perth. I will continue to fight for your rights, even if you don’t realise that you are being taken for a ride.

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