Reporting of Delignification in Pre Purchase inspections

Delignification is predominantly seen on roof tile battens in Perth.  If you are not sure what it is, or how it got there, please have a read here.

Reporting of delignification in pre-purchase building inspections has been a hot topic for a few years.

What do all the guidelines say?

AS4349.3 (Timber Pest Inspections)

Chemical delignification is specifically excluded from this standard.

AS4349.1 (Inspections of Buildings)

Definitions within this standard include:

Defect: Fault or deviation from the intended condition of a material.

Major defect: A defect of sufficient magnitude where rectification has to be carried out in order to avoid unsafe conditions, loss of utility or further deterioration of the property.

Structural defect: Fault or deviation from the intended structural performance of a building element.

Structural element: Physically distinguishable part of a structure.

What does all this mean for reporting purposes? 

One could argue that any material – be it a timber tile batten or rafter – that is covered in furry stuff following a process of chemical delignification, has deviated from its intended condition.  This means chemical delignification meets the definition of a defect.

To be classed as a major defect – this condition needs to

a) create an unsafe condition – not usually the case

b) lead to loss of utility – not usually the case (see below)

c) require remediation to avoid further deterioration of the property – this is the most likely area where there could be a case for reporting the defect.  Whilst not addressing the situation will most likely allow the chemical condition to continue, there is, as yet, no proof that we know of, that this actually causes significant deterioration of the underlying element within the standard life of a building.

Inspect WA’s guidance on reporting this issue can be found here.

What about the strength (utility) of the battens?

Inspect WA have been funding studies with university students to test the strength of tile battens that have been subject to delignification.  Whilst these studies are continuing, all testing to date shows that

1. Once you scrape the furry bits off the outside, the measurements of the timber beneath are not significantly different to unaffected timbers
2. The strength of the affected timber does not alter from its original or unaffected counterparts.

Is this a structural defect?

If only the battens have been affected, this is not classed as a structural defect as battens are not a structural element of the home.

If it is on the rafters, these will be assessed in the normal manner in the context of their contribution to supporting the entire roof structure.