LEAKY HOMES, Part 2: What’s going on inside your walls?
“Q: What’s your cladding for?
A: It’s to protect your building paper.”
- Old builders’ joke
THERE’S AS MANY MISCONCEPTIONS OUT THERE about what makes houses leak as there are so-called “experts” willing to take your money to find them.
First of all, all houses leak. Always have. It’s all about pressure: apply a high wind outside and you get high pressure. Close all your doors and windows and on the inside you get low pressure. If that reminds you of a vacuum cleaner, then it should. It’s pressure differences like this that make your vacuum cleaner work – and when the wind and pressure difference around your house are high enough, your weatherproofing systems are going to suck.
There’s nothing much you can do about that.
No house would survive under water – that seems pretty obvious. Even if it’s painted yellow, a house is not a submarine. Unlike a submarine, which is built with hermetic seals, then all houses no matter how they’re built are going to let water in behind the “outside skin” – which is what we call “the cladding.” The point is to make sure the water does no damage while it’s in there, and it gets out just as soon as it can.
For decades - nay, for centuries - most houses managed to do that pretty well. A decade ago in New Zealand we were building “mock Tudor homes” with modern materials, and they leaked. Yet five centuries ago they were building real Tudor houses (like that one on the right there) with branches and twigs over which was daubed a mixture of clay and sand and dung. Yes, dung. They called it “wattle and daub,” and surprisingly enough it didn’t leak, or at least didn’t cause major problems when it did.
And houses built here in New Zealand at the turn of the century with stucco over asphalt-impregnated paper – houses like that next one on the right -- they didn’t leak either, or at least didn’t cause major problems when they did. Yet last decade we were building “modern stucco” houses, and they did.
So what happened? For years we had no major problems, so what changed down in our neck of the woods that all of a sudden changed things? That’s the big question, isn’t it. What changed in the physical structure of your outside walls that caused water to get in and not to get out – and to cause real damage while it was there?
Well first of all, it wasn’t deregulation that caused all this. I talked about that last Thursday. But quite a lot did change that required bigger changes, but those changes never happened.
There’s probably some rule that someone can quote about this. Change one thing in a whole system, and other things can change to take account of that. Change everything in a system, and it takes some time to settle down – or to notice the ill effects of what just happened. In the early nineties, almost everything changed inside your outside walls, but other things never changed to allow for them. Something in particular. You’ve heard all the buzzwords: dry-frame, no eaves, Harditex, cavities stuffed with insulation, failing cladding systems, moisture content, stachybotrys . . . Let me see if I can explain simply what these all mean, and what caused the problem – and why no-one’s talking about it.
SO LET’S TAKE A LOOK at a typical outside wall – or at least a wall as you would have found it freshly built about ten to fifteen years ago. And to make it more interesting, let’s do it with a chain saw.
Let’s say you’re outside in your garden with your chain saw in hand, and you’re casting an eye over your house. Look up, and you’ll see the eaves – the part of the roof that hangs over the walls. Some of the houses that leak don’t have these, but just as many that do, do.
Now turn the saw on, and take a cut through your house’s outside wall. The first thing to feel the saw is the cladding. Depending on your house this might be any one of weatherboard, plywood, corrugated iron, brick or concrete block (which are going to cause major problems with your chain saw), or plaster or textured coating on fibre-cement board (which were what caused most of the problems with leaks).
Cut through your cladding, and the second thing to feel your saw is your building paper, which sits behind the cladding. Remember: your cladding isn’t a a hermetically sealed skin. Your cladding sits out in the high pressure zone, and sitting behind it in the protected lower-pressure zone is your building paper – which for decades was the plain black bitumen-impregnated kraft-based building paper that everyone knew and loved. And contrary to popular, and even “expert” opinion, it’s your building paper that’s always been your major line of defence when it comes to weatherproofing. Your building paper is supposed to allow condensation out of the house, and stop any water that gets through the cladding going into the house – and until ten to fifteen years ago it was doing that job damn well.
And don’t discount the amount of water getting through the cladding either: when it’s high wind and high pressure outside your walls, and low pressure inside, then you’re going to get water behind your cladding. Always have, always will. But install your building paper right, with proper laps and flashings in the right place, and you’ll make sure it doesn’t get inside your walls, and it gets away before it causes damage.
So let’s keep on cutting, and if we do we’re now going to start cutting into the walls themselves. Your walls are made up of vertical sticks of timber (“studs”) between which are nailed some horizontal sticks (“nogs”), to both of which you nail your cladding and staple your building paper, and between which you generally stuff insulation to keep you warm. If you keep cutting you’ll eventually get through this space (it’s only four inches wide) and your chain saw’s going to be cutting through the gibboard lining and into your house’s best room. Careful you don’t damage your sideboard.
SO THAT’S YOUR BASIC WALL, which now looks pretty messy after it’s had a chain saw going through it.
Now in the early nineties there were big changes from inside-to-out of that wall, changes that had nothing to do with “deregulation” (which is pretty much just the catch-cry of the cringingly ignorant) but which between them caused a “perfect storm” inside your wall – and I hang my head in shame at using that phrase, but it’s the perfect description for what happens when a whole bunch of things come together to cause an $11.5 billion problem.
Let’s look at all the changes.
1. Working from the neck up?
We share the stud-frame technology I’ve described here only with North America and with parts of Scandinavia, and our own methods are largely unique to us. So it’s moderately unusual, and for the most part the skills for it need to be learned here. That’s one point.
Here’s another. A timber-frame building is a ‘thought-built’ building. To build a timber-frame house successfully knowledge, skill and understanding are needed; constructing them properly requires that the builder work from the neck up – thinking as he installs flashings and building paper and other piece of weatherproofing kit; thinking about water paths, load paths and the like. About where water will be coming from, and where it’s going to go.
Sadly, many of the current crop of builders can’t do that much (even those “master builders” with walls full of certificates) because what they learned at their schools wasn’t always what they needed to learn. The complete story of the failure of New Zealand’s apprenticeship system is still to be told, but the body of knowledge that was once widely shared and passed on through the apprenticeship system, and on site by informal ‘mentors,’ has broken down.
Here’s another point. A timber-frame building is a ‘thought-built’ building, and most of the current crop of architectural detailers never learned how to. Some of the early examples and highest-profile cases of leaky homes, such as the 97-apartment Eden Two complex in Auckland or the 44-unit Marion Square Project in Wellington, were designed by registered architects (architects who won awards for them) but were detailed by young architecture graduates trained in schools that know next to nothing about construction technology; and they were put together by “master builders” who didn’t know much better. The results are predictable.
Here’s just one example of a particular problem at Eden Two: Un-tanalised dryframe timber was specified and installed in exterior cantilevered decks. The deck timbers you see in the picture at left, the bearers, were cantilevered out to support the decks. To stop water ingress to the balcony framing, building paper should have been taken over the top of the decks’ parapets and lapped under the building paper of the main structure. It wasn’t. But even so, if they bearers had been tanalised, these important structural members could still have survived. But they weren’t tanalised. They were dryframe.
The graduate architects simply read off their tables what they needed to do, the master builders erected what they had to do, the council’s inspectors okayed all that was done . . . and no-one, not on any of the ninety-seven units erected, ever looked at either the improperly installed building paper or the untreated bearers and said “That’s not right.”
The beams were specified by registered architects, installed by master builders, and inspected in accordance with the Building Act, yet no-one at any stage noticed the difficulty (and nor do they note the difficulty now when people say requiring architects to be registered and builders to licensed is going to solve similar problems in the future). The problem was not one of ‘insufficient regulation’: the problem was that each person who was party to these decisions was either untrained, uninformed, or simply unwilling to stand up and point out the problem.
2. Timber not worth the name
The studs inside your wall changed. Since the fifties your studs have mostly been built from plantation radiata pine, but two things changed recently to change what that meant.
First of all, for many years the radiata pine was always treated with boric acid, mostly to protect against insects like borer, but it turned out that “poking the borax” also protected against rot.
Second of all, while the pine used to be cut from trees that had taken longer to grow, more recent faster-growing timber turned out to have bigger “cells,” which means less strength, and more prone to rot. An ideal time, then, to introduce “dryframe” untreated timber in your outside walls. Or not.
Public choice theorists talk about how Bootleggers and Baptists will often find common cause – the “Baptists” calling for bans on things like alcohol because they don’t like them, the “Bootleggers” supporting those calls because the bans raise the price of their product. Something similar happened here with dryframe: chemophobes who claimed the boric salts were toxic and were poisoning the occupants joined forces with the big timber companies who wanted to charge more for selling less timber. The result was “Dryframe” – untreated timber that takes on water more readily, holds mould more easily, and rots far more quickly.
The vast majority of houses now being condemned were built with dryframe timber. But that’s not the biggest story here. That still doesn’t explain why so much water got in.
Silicone isn’t just popular in Hollywood, it’s been all the rage on New Zealand building sites for the last twenty years. Nothing wrong with that necessarily, but what happened was that folk forgot what flashings and building paper were for -- which was to remove the water that had got behind the cladding -- and they tried instead to use silicon to “face seal” the outside skin of the cladding; “face seal” it so that no water could get in at all. Can’t be done. A building is not a submarine. And because too often the silicone was used widely, but not too well, instead of keeping water out in too many cases it was actually blocking drainage paths and keeping water inside the building envelope. Remember the TV ad for example in which the late Augie Auer ran a line of silicone underneath his window sills? He wasn’t stopping water getting in, he was stopping it getting out.
So over-reliance on “face-sealed” systems was a problem. But this is still not the biggest story here. That still doesn’t completely explain why so much water got in.
4. Stuff the wall cavities
Live in an older New Zealand house in winter, and pretty soon you’ll complain about the draughts. Newer New Zealand houses don’t have the draughts because they have insulation in the walls, stuffed into those cavities between the studs. This is all the better for home-owners who are kept warmer in winter and cooler in summer – and for would-be National Party Prime Ministers, who offer the promise of better insulated homes to bribe voters with their own money – but not for the wall framing, which is all the worse now for the ability of wall framing to dry out if water does get in.
But that’s still not the biggest story here. That still doesn’t explain why so much water got in.
5. Those aftermarket add-ons
Increasing wealth means increasing add-ons to the outside of your home. Fancy installing Sky TV? An awning or two? A new pergola? All of these aftermarket additions add to the liveability of a home, but they’re all are much more difficult to install properly in a ‘plaster-look’ home – especially when the look is so convincing that installers often forget just what they’re screwing into. But penetrate the cladding of a monolithically-clad home, especially if the water can’t get out again, and you’re going to cause problems, just as many of these later additions have.
But that’s still not the biggest story here. These after-market bolt-ons caused some damage, but not all the after-market bolt-ons in Christendom caould cause the $11.5 billion catastrophe that now confronts the country’s cheque books.
6. Those dedicated followers of fashion
‘Tuscany’ is in. At least, it was. Tastes have changed very quickly now, but for a while there faux Tuscan was de rigeur. But Tuscany itself has a very different climate and totally different construction methods. In Tuscany they have plastered solid masonry buildings that artisans have been building for centuries – whereas here in New Zealand designers tried to emulate them using timber stud walls, which is something very different.
But where there’s demand there will always be supply. Cometh the hour, cometh the building systems – the most popular of which was James Hardie‘s Harditex – a medium-density autoclaved board made with wood pulp and cement that was used to back monolithic claddings. That’s what’s behind most of the “Mediterranean” looking houses you now see around the place with plaster walls, big entrances, ands tarpaulins and scaffolding all over them.
Despite the obvious problems with such a system, everyone at the time looked at the big BRANZ-approved tick this system had gained, and went to work with a will. After all, if it’s good enough for BRANZ – whose slogan used to be “BRANZ Appraised: Specify With Confidence!” – then surely it was good enough for Joe and Janet Home-Owner.
Well over two-thirds of the houses with leaky home problems were built with this system, built with a material systems that didn’t quite stack up, by installers and regulators who didn’t always understand the building science behind such buildings:
- Water got in, as it always will, but it couldn’t get out of them because the plaster was taken right down to the ground.
- And instead of accepting that water would get in past the cladding and then detailing the system to suit, the “Tuscan look” called for “face sealed’ systems, and almost forgot about the building paper and its associated flashings altogether.
So the building paper was still there, even with this system, but it had often been forgotten about – and something else was going in inside the walls that meant even when it had been installed properly it was about to disappear.
That something was a mould called stachybotrys, and it doesn’t just eat children’s lungs, it also consumes building paper. That is the bigger story here, and it became a bigger story than it needed to because of one other change that happened in the decade before the nineties. It involved asbestos.
6. From asbestos to wood pulp
The use of asbestos goes back more than 3,000 years. Its stability, high tensile strength and resistance to chemical and moisture-induced degradation made it an ideal fibre to be used in James Hardie’s fibre-cement “Fibrolite” boards, sheets and “HardiPlanks” – and the many fibrolite buildings and baches that still inhabit the country’s beaches are a testament to just how stable Fibrolite used to be. When I first started building, we were still cutting up sheets of “fibro” with our angle grinders, and throwing the off-cuts into fires to hear them explode.
But in the early eighties it became clear even to the miners and manufacturers of asbestos that it was killing people. Fact is, it had been known since 1906, but the miners and manufacturers and other users of asbestos were reluctant to concede the point publicly, so when asbestos mining finally ceased in Australia in 1983 they had to quickly cast around for a replacement to use in their fibre-cement sheets. What they came up with was wood pulp – cellulose fibres that were asked to do the same thing as asbestos, but don’t.
Fibre-cement sheets used to be stable. They used to resist water penetration. Now they don’t. Get water in behind a snugly fitted medium-density fibre-cement board these days and it’s going to soak in there for the long term. It’s going to soak in, it’s going to incubate, and it’s going to emerge after a short time as stachybotrys. And so it has.
7. From building paper to no building paper!
None of the changes mentioned so far would have been fatal on their own. If water got in, it should have been protected by the building paper. If the building paper was badly installed in some few places, it still would have protected the home-owner in every other place. (Even on the Eden Two apartments, the installation errors only occurred in the same one or two places on every apartment).
Remember that building paper is that black stuff that goes around your framing before the cladding goes on. Some years ago when I began working on building sites I was asked the standard joke. Q: What’s the cladding for? A: To protect the building paper. The reason it was a joke was that everyone understood the punch line.
But what protects the building paper when stachybotrys does come a’calling? Then that’s no joke at all. Stachybotrys is the toxic mould you hear the most about. As one consumer website explains, Stachybotrys chartarum is “a slimy, greenish-black mould that grows on moisture-laden materials that contain cellulose [or wood pulp], such as wood, paper, drywall, and other similar products.”
Stachybotrys just loves the sort of cellulose-rich fibre that can be found in paper, carpet backing, wood fibre board such as MDF . . . and in today’s fibre cement sheet. As one learned academic paper explains,
“fungi possess the ability to degrade lignin … (Blanchette 1984; Eriks ksson on et al al. 199 1990). This is a sought ought after effect especially by the pulp and paper industry, as selective … fungi not only have a bleaching effect of the wood pulp … they further cause, through their degradative action, a loosening of the cells.”
et al al. 2003).
Sought after it might be in the pulp and paper industry, but not sought after at all in the building industry! Particularly not when the very same cellulose-rich fibre found in Hardie’s fibre-cement boards, and used as a backing for most of those monolithic claddings, is also used in the building paper behind it.
When that’s the case, and you get water in behind the cladding, then can you take a guess what you’re going to find?
That’s right. No building paper. If you take a close look at that picture above, which comes from a building built by master builders and designed by registered architects, and which is clad with James Hardie’s Harditex over which a solid plaster skin has been applied, you’ll see that what used to be the building paper protecting the building is now those few scraps of paper as brittle and ineffective as an All Black defence under the tutelage of John Hart.
It’s just not there any more. It’s been eaten away. As you can see, the studs in the picture above have already been replaced preparatory to a reclad, but the building paper that used to be the home-owners’ primary protection against the weather has just disappeared. It’s been vaporised. It’s been eaten up – just like those home-owners’ dreams, and their life-savings.
It’s a fairly simple formula here, one known about for years in the pulp and paper industry but not publicly at least by those in the building research or fibre-cement industries – a simple formula that looks like this: in the presence of wood pulp, building paper plus stachybotrys equals . . . no building paper.
If you want to know what’s been been going on inside so many New Zealand walls over recent years, then that’s it.
And if you like your stories simple, then that’s about as simple as it’s possible to make this one.
And the story has another fairly simple back-story – another story that remains still to be told, but one appropriate to a story about cladding since the phrase that springs to mind here is “cover up.”
Because the big story here, which I haven’t seen addressed anywhere else before and which is another one for investigative journalists to get there teeth into – if there really were any here in New Zealand – is this: answering the question “Who knew about this before it happened?”
It’s a fair question because the big players both have past form.
Just as the research on asbestosis was out for years before being publicly acknowledged by manufacturers – acknowledged only in the wake of a series of expensive legal suits for which governments are still bailing out their cronies in the big companies – so too has the research been out there for years showing the effects of stachybotrys on cellulose fibres, on wood pulp and kraft-based papers.
And just as the government was able to protect the Building Industry Authority’s bureaucrats from harm’s way by changing its name, so too you’d hardly be surprised if they did what they thought they needed to do to protect their bureaucrats at places like the so-called Building Research Association. After all, they’ve already made the company once called Building Technology Limited 1995 disappear, which was once (see below) the “company wholly owned by BRANZ” which issued all those nifty appraisals back in the day, and which are now worth less than the wood pulp on which they’re printed.
So who knew, and when? Did James Hardie? Did the government’s so-called Building Research Association? What did they know, and when?
And how come it’s builders and designers who are getting the blame for all this, and builders, designers, rate-payers, tax-payers and home-owners who have to pick up the tab?
I think we should be told, don’t you?
- Earlier in Part 1: The myth of deregulated building
- Coming next in Part 3: How everything that’s been done since the problems were discovered has made life more difficult for almost everyone.
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All care & no responsibility? The front page (below) of one of many failed appraisals issued by BTL “a company wholly owned by BRANZ,” which is a government quango. This appraisal, for Duraplast on Hardibacker, is for one of the more high-profile leaky home failures. BTL no longer exists in that form, and the “researchers” at the government’s Building Research Association of NZ continue to shirk responsibility . . .