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Weathertightness of new buildings

Recently I wrote an article on weathertightness basics as part of feature in the Oct/Nov issue of BRANZ Build magazine. There was an excellent range of articles from local and central government , a lawyer, BRANZ scientists and from technical writers.



Recently I wrote an article on weathertightness basics as part of feature in the Oct/Nov issue of BRANZ Build magazine. There was an excellent range of articles from local and central government , a lawyer, BRANZ scientists and from technical writers. Usually such articles disappear into the ether, however this time I received some rare and encouraging feedback;

“I thought you might like to know that a reader – an architect – contacted BRANZ to say how much he liked the latest issue of Build, your article in particular.”

As any writer would appreciate, someone going to the trouble of showing their appreciation is really valued. So I’d like to share with you some pieces from my article. You may want to read it in full and some of the other articles, so go to:

Weathertightness basics

Following the widespread use of cavities, introduced with the revision of Acceptable Solution E2/AS1 in 2005, and the return to boron-treated timber, our understanding of weathertightness is far ahead of what it was in the 1990s and early 2000s.

The 4Ds

The 4Ds concept of deflection, drainage, drying and durability, developed by Canadians Paul Morris and Don Hazleden in 1999, is the overarching principle underpinning E2/AS1. Here I only consider the first 3Ds in relation to wall assemblies.

Cavities provide drainage and drying

The primary purpose of a cavity is for drainage and drying, but it offers so much more. It separates less durable wall framing, insulation and internal linings from more durable wall cladding elements – cladding, external joinery and flashings. I call this the dry side, wet side principle.

Accordingly, certain flashings in E2/AS1 (such as saddle flashings) have been kept on the wet side rather than bridging to the dry side. That idea still seems to be novel to some. This E2/AS1 solution contrasts with the additional complexity of saddle flashings used in British Columbia that cross to the dry side (see Figure 1).

Be sparing with battens

The ideal cavity is empty with no battens except those necessary to support the cladding. So less is best with battens.

My preference is vertical battens only, as is the practice in British Columbia, Canada. If intermediate support is needed, short vertical battens can be used. It’s also much easier to inspect vertical-only battens, accidental blockage is reduced.

Better drying with top venting

BRANZ testing has confirmed that, while bottom venting provides enough drying, top venting allows greater drying potential than bottom-only venting. Top venting is common sense. Vapour – water as a gas – is buoyant in air. Invisible vapour rises until it gets cold and condenses into tiny water droplets and becomes visible as clouds.

Therefore top venting allows buoyant vapour to escape to the outside rather than becoming trapped at the top of cavities. Air in the cavity also warms and rises – the stack effect – as the cladding and joinery are heated with sunlight or internal warmth. Both these effects produce a conveyor belt of drying.

Differential wind pressures top and bottom of cavities also create air movement both up and down – it is important to keep the openings on the same face to avoid ventilating between positive and negative pressure zones and creating too much air movement.

Bottom vents can get blocked

Not only are well detailed top vents considered beneficial, they also provide redundancy. Bottom vents can be readily blocked – more often than most realise. For example, landscaping levels can rise as mulch is added.

Brick veneer requires venting to avoid drawing air from subfloors or venting into roof spaces. The same care of where to draw and discharge air applies to all wall cavities.

Top venting allows more rapid and reliable pressure moderation. I use this principle with windows set into concrete and concrete masonry walls. Sill details can be problematic as they are the opposite of a good rainscreen, so I vent at the head as well. This gives more reliable pressure moderation and better drying of the cavity between the fame and wall.

At the junctions

All cladding junctions are best formed by providing an effective rainscreen, a drained cavity and an air-barrier – that’s all! A rainscreen separates water from air, which then enters and balances cavity and external air pressures. Once equalised, there is no driving force to propel rainwater across the cavity.

Compartmenting cavities

Any building subject to wind has a wide variance of positive and negative wind pressures over its various faces. The face exposed directly to the wind typically has positive pressure, whereas the side and rear faces typically have negative pressure. Wind speed, and thus pressure, also increases with height, due to less obstructions and ground friction.

So, to improve pressure moderation on larger buildings, we divide the cavity into compartments, both vertically and horizontally, and especially at external corners where there are adjacent positive and negative pressure.

Car door excellent example

If in doubt, consider your car door, as this works well. It has an interior air seal that keeps out the road noise and dust and a drained cavity between the door and car body that also provides the rainscreen. The gaps that are large enough so water can’t block the air flow needed to achieve pressure equalisation. It’s a good reminder of how we should design and construct weathertight building envelopes.

Written by: Philip O’Sullivan


How to Choose and Purchase a Suitable Property to Subdivide




With the demand for housing in Auckland at peak levels and even smaller-scale properties showing substantial profit margins when sold, subdividing a lot into two or more sections has huge earning potential. Those with the means and capabilities to purchase land for the purpose of subdividing are almost certain to see a large return-on-investment, that is of course, as long as it is done correctly.

Choosing a property to subdivide while exploring real estate options requires the assessment of a multitude of factors. Whether or not a property is capable of being subdivided will depend on its size, its location and the physical layout of the property. It’s not always as easy as choosing the biggest section out there and splitting it down the centre.

Considerations are not just restricted to feasibility either. Property investors taking this route should always keep profitability at front of mind. The effort put into the property needs to be reflected in resale value. At times, just because you can subdivide, doesn’t mean you should.

Factors to Consider When Looking to Purchase a Property with the Potential to be Subdivided

The Size of the Property

When it comes to subdividing, size definitely does matter. Generally, the larger the section the better the earning potential will be. On the other hand, it’s important to keep in mind that section size will also affect overheads. Larger sections typically incur higher costs while performing due diligence.

Land Layout

Level land is important, it will be easier to build on and will be more appealing when it’s back on the market. If a potential section is uneven or has landscape issues, it can make property development more difficult. Choosing a property that is already level will allow a smoother process.

Steps should also be taken to assess how easy it will be for multiple households to live on the lot. Consider issues like driveway creation, road and utility access, and street frontage. These factors will affect council consent and appeal once you’ve placed your subdivided property on the market.

The Zoning Rules of the Area

How the area the property is located in is zoned will restrict the type of housing you are able to create and can even cancel out any plans to subdivide. Before purchasing a property, it is crucial to research council zoning restrictions and consider how they will dictate your subdivision plans. Choosing to work with a subdivision consultant will help you navigate this process if you aren’t sure about taking it on yourself.

Subdividing is one of the most profitable actions a property owner can take. The ability to sell two lots from the purchase of one can exponentially boost your earnings from your investment. Council restrictions and market appeal will have an impact on how your subdivision journey will play out. However, with these considerations taken into account while you search, it is entirely possible to choose a property that will offer worthwhile returns.

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Another date NZ property investors are dreading



key in door

How scary is the new ring-fencing legislation?

Well, just ask any property investor, most of whom are ma and pa investors with less than three rental properties and they’ll tell you it’s outright frightening.

They are the investors, most likely to be among the 116,000 already declaring a loss on their properties and times look set to get tougher for them where selling up may be the only way out.

Ma & Pa Investors Are Not Greedy Landlords

Ma and Pa investors are not your ‘greedy landlords’ with huge portfolios.  They’re middle aged workers (GenX, Baby Boomers) and retirees, motivated by the need to provide their own financial security in retirement.

For years the message from those in the know has been: we’re living longer and the Government pension will not be enough to live on.

Taking matters into their own hands, ma and pa investors have heeded this advice and parked some savings in one or two rental properties.  However times have been tough in recent years and the not so greedy landlords have seen any profits they had eroded.

Weekly rental increases have been modest for months.  Some may balk at this but yes, the evidence is on the Trade Me Rental Price Index and on this blog too.

Property investors have been sideswiped with increases in running costs, which they have had no choice but to absorb initially, before passing them on in the form of incremental rent increases and now there’s another law to halt that with only one increase permitted every 12 months!

See this news item on Stuff, 116,000 rental property owners declared a loss for the year ending March 2017, and it was during the lead up to, and including, this financial year, that legislation changes really started to bite and property expenses started to far exceeded income.

On blogs, property accounting and finance professionals like GRA have provided their interpretation and opinion on legislation changes and forums like our PropertyTalk give a voice to investors and their sentiment.


The ring fencing law will stress out many property investors further, and some to the point of no return.  Yes, landlords will sell, so more properties will come onto the market and many first home buyers will happily snap them up.  For those amongst us that are politically motivative,  they’ll only see the upside.

However there’s a downside too, that’s not been mentioned much.


Rentals typically house more people that first home buyer (FHB) homes.  So for every rental property subsequently bought by a FHB, two people are left without somewhere to live.

Housing has been a hot political potato for so long it’s been one step forward and two steps back irrespective of which party or parties are in power and so there’s no end in sight to this housing crisis madness.

Not Just Local

Targeting the rental property owner has been popular not just locally, it’s been a justifiable fear for landlords in the UK, America, and Australia.  Check out the links below.

So is there a country getting housing right?  Let us know your opinion in the comments below or in a blog post on PropertyTalk or of course in our discussion forums.

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Would You Be a Landlord in 2018?



Investing in residential property has well and truly lost it’s shine in 2018, especially in the state of Victoria and New Zealand.

In the UK, Landlords are more philosophical about changes to tenancy laws.

A recent survey suggested around half are actually positive about Land-lording even with the obvious challenges ahead namely Brexit and the political climate.

As aforementioned, can not be said down-under where landlords feel they’re wrongly in the line of sight of politicians for political gain and thus the law changes are not balanced and swing too far in tenants favour.

So the question is would you be a new Landlord in 2018?

Hindsight is a wonderful thing as the saying goes, and many property investors who have been in the property investment industry for some time still love it and already do well by the tenants which really is just commonsense.

However going in now with your eyes wide open and in the knowledge of the recent law changes, increases in everything from insurances to rates and the talk of tougher times ahead – is property investing a good move? For long term investment – why not?

Speculative property investing (though it’s hardly investing) has always been cyclical and when it’s grouped under ‘property investing’ it gives long term buy and hold Landlords a bad name.

Speculators will come and go as the property market moves through it’s cycle and their activity is considered a business and incurs Capital Gains Tax.

Long term buy and hold investors know it’s always been about the numbers and making sure they add up and there is some fat left in for the unexpected expenses.

However the constant politicising and changing of the rules to suit political agendas is disruptive and it’s hard not to think there’s a conspiracy against Landlords and it’s not just in Victoria our New Zealand, it’s more far reaching and this must be putting off would be investors which will be problematic since private landlords supply most of the rental stock.

The UK Landlords must be made of tougher stuff though as 64 percent say they’ll carry on regardless, keeping their rental properties, focusing on the potential of long term profit. The idiom “soldier on” holds firm on the land of the white cliffs of Dover.

Back down under the confidence is not so high among the local property investors. It’s one thing after another and there’s been a lot of change thrown at Landlords in recent months.

The bright line test, LVR rules, and more recently revision of the bright line test to five years and legislation around the quality of the properties.

Insulation, heating, moisture extraction, you name it New Zealand rental properties are getting a hammering from Government. But none more threatening than what might come from the Tax Working Group headed by Sir Michael Cullen.

There’s a lot on the table aimed at raising the tax grab, including Capital Gains Tax and more recently talk of a Property Value Income Tax. If you screwing up your eyes at this one, you’re not alone.

It’s creative for sure, and if implemented, it’s likely to be the tipping point for Landlords unsure if they’ll ‘soldier on’ or sell up and run for the hills.

What’s most perplexing Landlords, is why the sole focus on them and not a balanced effort to improve both the conditions of the suppliers of rental properties i.e. the landlords and it’s inhabitants, the tenants.

Surely the relationship is symbiotic and thus both are needed, now that ever before with homelessness increasing and home affordability out of reach for first home buyers everywhere you look.

Here are some great discussions on various topics affecting the viability of landlording today in New Zealand.

Capital Gains Tax?

Consultation on proposed RTA changes

Tax Working Group

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