Friday, April 10, 2015

Post/beam connections – Practice vs. Compliance

Here are some perfect examples to show different results from good building practices vs. details in accordance with NZBC AS1 or NZS 4306.

A good building practice:

Post/beam connections simply sandwiched with nailed 4x2 on each side. The connection was built 35 years ago and showing no deformation at all.
Today if you draw that detail and apply for a building consent, you need specific testing to verify that this detail would meet our Building Code.

A detail in line with NZBC AS1 and NZS 4306:

The post/beam connections are fixed with stainless nail plates on each side. Connections are severely deformed and twisted. By the way the details have formed at 2009.

So, as a pre-purchase building inspector, how do we judge the above details? 

It is simple when you know the first detail has formed some 35 years ago. But what about if same detail is formed today? Do you raise concern due to deviation from our Acceptable Solutions/Standards or happy with that? Do you believe same timber sandwiched post/beam connection formed today will be able to perform for at least 35 years?

Are there leaky type claddings?

A very common question is: the house is clad with xxxx, will it leak?

In my past 6 years of inspection I never found any leaky house, which leaked purely because of cladding type itself.

Similar question is studied in a recent Branz Bulletin – Ventilation drying behind wall claddings, the question is:

Are some cladding types more leaky than others?

The findings are quite surprising for many people:

Low leakage claddings:
New freshly painted weatherboard walls
Well maintained continuous sheet claddings,
Metal and PVC weatherboards with tight-fitting overlaps and effective jointers at corners
Average leakage claddings:
Well maintained painted timber or composite weatherboards with few obvious defects
Leaky claddings:
Warped and cracked unpainted weatherboards
Non-rendered brick veneers

Two interesting notes to be made here:
  1. ·         Combination of factors such as build quality and maintenance rather than cladding type itself will determine the leakidity (how likely to be leaky) of a cladding.
  2. ·         More publicly accepted leaky types of cladding, such as sheet cladding, are not listed under leaky cladding. Well-reputed cedar weatherboards and brick veneer are summed as leaky claddings.

But there is one fact which is commonly agreed by everybody: Most leaky buildings are monolithic clad buildings. But can we rephrase it as: monolithic cladding likely to leak? Wanted or not, majority of public think that way, and that is the main reason why monolithic clad houses are selling with discounted price. 

I have always enjoyed in challenging public perceptions, here are my questions:

If you simply replace the cladding of leaky buildings with weatherboards, but without redesign junctions, joints, ground clearance, balcony details, will you stop leaks? The answer is No.

Or put the other way: we build two houses, one with direct fixed weatherboards, another one with direct fixed fibre cement sheets, all with untreated timber framing, all with no clearance to ground surface, all with fully enclosed membrane balcony, all with windows without any flashing, all without eave overhang, all with poor workmanship to detailing. Will the weatherboard house be survived when fibre cement house be leaking like shit? The answer is No.

If cladding type is not the one to blame, what to blame? Design? Workmanship? Then the whole Country likely has targeted the wrong thing again. Looks like we no longer building any plaster houses, which itself never been the reason causing leaky building issues. But we have not improved anything from design and workmanship point of view. Will that mean another construction disaster in the near future? We will see.