What’s going on with shrinking timber weatherboard?


Building Today columnist and industry stalwart Mike Fox talks candidly about issues concerning the New Zealand construction industry.

With the swing away from monolithic claddings towards more traditional-looking homes and claddings, finger-jointed timber weatherboard manufacturers have probably never had it better.

However, personal experience has led me to realise timber weatherboards potentially have their own set of issues.

In the past 24 months, on no less than five separate occasions, we have personally experienced severe shrinkage problems with pre-primed pine weatherboards. All of these have resulted in expensive repaints with varying degrees of success.

In addition to this, there have been many boards that leach out sap which also need rectification work.

Obviously this is a worrying pattern, so I decided to seek assistance from the manufacturers, and this is where it gets interesting — or, might I say, disappointing.

Our painter, who completes more new exteriors than most for a variety of builders, shared with me that we are not experiencing this problem alone, and that these are certainly not isolated cases.

The problem may well be more widespread than it first seems, and it would be useful to get some feedback on the extent of the issue.

The homes in question here are in different locations, have different designs, different carpenters, different colour schemes, different painters and paint manufacturers, and they were also built at different times of the year.

The only common factor between all the projects was the substrate which, in all cases, was pine pre-primed, finger-jointed, bevelled-backed weatherboard, albeit from two manufacturers.

The other consistent factor is that neither of the timber weatherboard manufacturers have had any interest in resolving the issue other than blaming the builder, the weather, the painters or the paint manufacturers — anyone but themselves.

One manufacturer’s representative went further to say that it was a race to the bottom price for supplying the board, and that, ideally, all board should be double-primed at the time of manufacture, but it would make their product more expensive.

By not doing this or improving the product, they push the problem of shrinking boards on to the unwitting builder and consumer.

Ironically, the eventual outcome of ignoring the problem will be a march away from their product. No builder wants to use a product that gives them or their client issues, and unless this problem is resolved at source they will vote with their feet. It is naive for a manufacturer to expect anything else.

Another builder I spoke to who had also been having board shrinkage problems fitted some of the acclaimed double-primed boards to see if this would make a difference.

The outcome on this project was a similar result — board shrinking during the summer months leaving a visible line of undercoat, and then the board swelling back somewhat in the winter months. So much for that theory, and this builder now will not use timber weatherboard.

One weatherboard manufacturer visited one of the sites in question and quickly walked away, saying it was our problem. What great PR, and just what a builder wants to hear. We go out of our way to make sure their product does not now get specified.

Another manufacturer decided to take samples of their product and said it was the paint that was at issue. We had the paint manufacturer do their own inspections, and they said it was the weatherboard at fault — so where does that leave the builder and home owner? — once again flapping in the wind with an expensive problem they haven’t necessarily created but are now having to resolve.

So what is going on here? It would appear that, anecdotally, pre-primed, finger-jointed board may not be the product it used to be.

Is it that the profile is now smaller and the timber less seasoned? Is the timber of lesser quality or the undercoat thinner? Should the board be painted before installation? Should the board be fitted at the height of summer only?

I don’t know the answers to these questions, but it appears the product has become more precious than it used to be and, unless you are very careful with its installation, you may well be up for an expensive repaint within 12 months.

Given the financial risk associated and the manufacturers’ “don’t call us” attitude to the problem, we have taken the following pragmatic steps to avoid having issues with pre-primed weatherboard:

Those projects that were already under construction have had an additional coat of the final colour applied to the face of the board before it is installed. This doesn’t stop the shrinkage but it does disguise the shrinkage line when the board pulls back at the height of summer.

Sales consultants have been instructed to inform clients about the shrinkage risks of using timber weatherboard and, if the client still wishes to use it, it is documented that it is at their own risk. Not ideal at all.

We have completely migrated away from using or recommending the product on future projects until proven preventative remedies and accountability have been identified. We just can’t afford the financial or reputational risk as it has become abundantly clear you are on your own if a problem occurs.

Because of the way the law operates in New Zealand, builders who supply products end up guaranteeing those products, even when a manufacturer walks away or is not there to assist.

If the leaky building saga has taught us anything, it is to make sure that products are fit for purpose and that they are backed by solid and responsible manufacturers.

Unfortunately, it has proven far too easy to blame the builder and get away with it. The builder often fixes problems with marginal product rather than battle tardy manufacturers.

Accordingly, I would recommend you are very careful with the products you recommend and use. Ask yourself the following — will these products stand the test of time, and will I get assistance if they fail prematurely? If you can’t answer those questions affirmatively, don’t use the product.

This article contains the author’s opinion only, and is not necessarily the opinion of the Registered Master Builders Association, its chief executive or staff.

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