How to tell if a house is built with treated or untreated timber?

[lamboflight]

Hi everyone! I am new to this forum but have been reading forum posts from time to time. I would like to seek your advice regarding the leaky home issue. I have read that houses in the 1990's to early 2000's were often built with untreated timber which have high risk of being leaky homes. I would like to ask what is the best way to find out whether a house was built with treated timber or not. Sometimes I see that the building plan in the LIM report of some houses mention 'kiln dried timber framing' - does it imply 'treated' timber was used? Or is it that the actual material used can be different from what's written on the building plan in the LIM? Are there any other ways of finding out? Perhaps the council keeps some documents other than the LIM that can tell us about the timber used?

Also some places say the rule about the type of timber used was changed from 1998, some say 1992 or some say 1995. Would anyone please shed some light about when was the actual year of untreated timber began to be used?

Thank you all in advance!!!!

[Ivan McIntosh]

Kiln dried timber framing is usually untreated and one of the main contributors to rotten framing from leaky homes. Mind you, if it never got wet there wouldn't be an issue...but how many houses in reality never leak anywhere? Not many.

[garrett]

Untreated pine framing was introduced most likely in 1996 after the standard NZS3602 changed in late 1995. Douglas fir was used untreated prior to this date as it had better natural resistance.

The period UT KD was used the most for external wall and roof framing was 1997 - 2003. Note that H1 LOSP treated framing was also kiln dried during that time, often after the boron treatment, so some of the treatment would be lost in the kiln drying process. Combine that with a decrease in the amount of boron required to be called H1. H1 framing at that time had a boron retention of 0.1 w/w, compared to the previous 0.4 w/w and the current 0.8 w/w. So even if you did have "treated" timber it may be not much better than untreated.

You can not rely on markings from manufacturer due to mislabelling occurring more often than it should have. Spot testing the timber using turmeric acid will tell you if boron, tin or copper is present (depending on the colour change to the acid if at all) which indicates H1, H3.1 LOSP or H3.2 treatments respectively, however, the spot test does not tell you how good the treatment is. For that you need to send the timber for laboratory analysis to determine retention.

[klauster]

Treated timber - That is what the change of building code tells us – treated timber resolves the leaking house problem. Possibly leaking houses last longer.
And what is with the vapour of all that poisoning stuff in kid’s bedrooms? The exposure to breathing disease etc – and after few years the building code get switched back to complete the cycle of changes. Funny, isn’t it?

[lamboflight]

Thank you all for your replies. It looks like there is no easy way to tell what type of timber a house was built with. Would you then suggest avoid buying houses altogether from that period? It seems like not even builder's report can find out the type of timber used, it will at most check for moisture level.

What about houses built with brick wall and concrete-tiled roof, but untreated timber as the framing? Are they worth buying or still risky?

[NZGEMS]

I think it is more expensive, especially now but I build a few houses 5 or 6 years ago and they did some of those with steel framing, that wont rot! Sure it can still be done, perhaps it is worth the slight extra expense for peace of mind.

[garrett]

I think it is more expensive, especially now but I build a few houses 5 or 6 years ago and they did some of those with steel framing, that wont rot! Sure it can still be done, perhaps it is worth the slight extra expense for peace of mind.

Replace the word "decay" with "rust" and neither framing type stands out above the other.

[Perry]

From a building certifier's e-mail to me.

The real issue with the building is very likely to be the timing of
construction as at that time dwellings were being constructed with
un-treated (laser frame etc) timbers and the cladding systems were
being directly fixed to the framing (not having the now required
drainage cavity). It has been discovered that all of NZ homes have
been leaking in a very minor way from time immemorial but such small
amounts of moisture did not affect the building structure and quickly
dried out. With the introduction of un-treated framing timbers the
very small amounts of moisture (along with the density of the
timbers), decay and fungal growth occurred rapidly and the timbers
quickly rotted. Those large companies responsible for convincing the
Government did not accept any responsibility and claimed that the
Government approved the use of the timbers (not the large commercial
companies). The government have also refused to take any liability
placing the responsibility onto Councils who in turn laid the blame on
the designers and building contractors. The government has then
actively gone about condemning all homes constructed in this manner
without fully identifying the cause on a case by case basis and even
instructed the so called "experts" to where at all possible place all
liability and duty of care back onto the property owner.

Unfortunately this home would appear to be tarnished by the other
failed buildings of similar age and design which has made the task of
the real estate agent very difficult. From a real estate agents
perspective why would they push for the sale of these buildings when
they can sell a newer building (which has treated framing timbers).
Presently I believe there are a good supply of homes for sale in this
standard and price range. I would guess that the agent has not put in
maximum effort in the marketing of the property for the above reasons.

The dwelling concerned was inspected by said certifier
and the report sold the house within days.

[lamboflight]

Thanks for the forwarded email! What kind of cladding was the dwelling built with?

[lamboflight]

Replace the word "decay" with "rust" and neither framing type stands out above the other.

What's your view on houses built with brick wall and concrete-tiled roof, but untreated timber as the framing?

[Perry]

Thanks for the forwarded email! What kind of cladding was the dwelling built with?

I think it was called insulclad. But the house structure that was visible, such as the roof trusses, were all untreated heart
of parsnip. (aka pine). Many 'leaky buildings' used insulcald, so this one suffered by association. The nub of the matter is this:

It has been discovered that all of NZ homes have been leaking in a very minor way from time immemorial but such small
amounts of moisture did not affect the building structure and quickly dried out. With the introduction of un-treated
framing timbers the very small amounts of moisture (along with the density of the timbers), decay and fungal growth
occurred rapidly and the timbers quickly rotted.

What he effectively said was there were three layers to moisture proofing.

1. Outside cladding
2. Building paper
3. The timbers (if treated)

. . . and previously, the (treated) timbers had not been regarded as a layer of 'moisture proofing.'

[Maccachic]

There are 4

Deflection
Drainage
Drying
Durability

http://www.branz.co.nz/cms_show_download.php?id=7676de6f955ebbd12c1400f3859c1a735183fbd8

[garrett]

What's your view on houses built with brick wall and concrete-tiled roof, but untreated timber as the framing?

If the house has good eaves and few roof penetrations, and if the brick is installed properly with brick ties angled downwards from stud to brick, the cavity is left free to drain with no mortar castoffs chucked in that block vents or form a water bridge across the cavity and penetrations through the brick are all done properly - I would then consider the risk to be much lower than monolithic clad houses, but not as low as the same brick house with treated framing.