Tackling residential building quality

This Issue This is a part of the Building better feature

By - , Build 179

There’s plenty of cracks to be found when examining why poor-quality residential builds are so common. A look at the number of requests for further information for each building consent tells part of the story, as does the rate of inspection failures.

THE CONCEPT OF quality in construction is often considered in terms of functionality, performance and durability. Here, I’ll look primarily at durability. This was recently defined as ‘the ability of building materials, components and construction methods to satisfy performance and functional requirements of the New Zealand Building Code for the expected life of the building, without a reconstruction or major renovation/repair’.

Where quality shortfalls emerge

Some recent examples of poor quality range from inadequately installed insulation through to poorly poured concrete floor slabs and problems with steel mesh and reinforcing bars.

The process to help minimise or eliminate residential construction quality control problems must address the most common issues with the most pragmatic possible solutions. So, what aspects of design and construction struggle to meet the minimum standards of quality?

Quality starts with good design

Step 1 in the construction process is the design phase. The ultimate standard of the final dwelling begins with the quality of the design and documentation for the project.

Building Research Levy funded 2018 research analysed requests for further information (RFIs) during the building consent application process. These are the questions the building consent authority asks of the building consent applicant to establish or clarify whether the proposed building will meet Building Code requirements. Here, we are considering whether building consent documentation is of sufficient quality, with quality defined as meeting the minimum standards of the Code.

Data was examined from building consent applications for 2,035 new residential consents of various increasing construction complexities from R1 to R3. The average building consent application generated 10.6 RFIs, while the highest was an R2 complexity application with 123 RFIs – if any readers can beat that, I’d love to hear, anonymity guaranteed!

A quick look at the proportion of the RFIs by Code clause makes interesting reading too. Clause B (including B2 Durability but predominantly B1 Structure) generated almost 37% of the RFI requests, while clause E Moisture (predominantly E2 External moisture) accounted for 24% of requests.

Education part of the answer

Education must be at least part of the answer to improving the competence and performance of the designers and architects designing our new residential building stock. Identifiable major areas such as B1 and E2 should be the initial focus. I have anecdotal information that the younger designers and graduate architects are generating the most RFIs, so how do we focus the education where it is most needed?

Rather than learning on the job by correcting the documentation in response to building officials’ RFIs, we may need to improve the education and skills imparted to these designers, targeting topics such as B1 and E2. Some of the obvious potential change agents may be the university schools of architecture, polytechnic institutions and other postgraduate advisors and industry educators such as BRANZ and MBIE – even Kāinga Ora and Te Puni Kōkiri for papakāinga.

A quarter of inspection fails for structure

Step 2 is the actual construction of the dwellings. Other research has looked at the percentage of failed site inspections on residential building sites to gauge how prevalent the quality issues were during the build. Of the 3,195 site inspections that were looked at, 260 (or approximately 8%) had failed. While the reasons for the inspection fails were harder to specifically identify, the largest single cluster (approximately 25%) of fails was grouped around work pertaining to Code clause B1.

Also of interest was the spread of inspection failures by size of building contractor. Earlier research broke down the residential construction sector to show:

  • Large builders (30+ residential dwellings per year) make up 1% of the industry and build 37% of the new dwellings.
  • Medium builders (7–30 dwellings per year) make up 3% of all builders and build 12% of dwellings.
  • Small builders (fewer than 7 dwellings per year) make up 96% of builders and build 51% of dwellings.

Inspection fail rates by builder group were recorded – large-scale builders failed 6.9% of their total, medium-scale builders 8.3% and small-scale builders 10.6%. Interestingly, more-complex buildings did not necessarily attract higher rates of inspection fails – R3 buildings had a fail rate of 7.7%, while the fail rate for less-complex R2 was 9.4%.

Bigger companies have fewer fails

These studies suggest that there are two strategies for influencing quality during the residential build process:

  • Focusing on the 4% of medium and large-scale builders who record the highest levels of quality across 50% of residential new builds. How do we encourage this group to lift their quality even further?
  • Focusing on the 96% of small-scale builders who record the lowest levels of quality across 50% of new builds. This would require influencing most firms who may have a wide variation of business operating models, special market focus and capacity to upskill and who by definition operate as independent units.

Neither are an easy fix. They would need targeted strategies to make inroads and positively modify these levels of performance.

When we seek to address building quality issues, we must remember almost every building in the country is a one-off to some degree. Even apparently identical structures will have been tailored to suit their site conditions, location, bylaws, hazard zones and budgets. There are no single fix-all solutions to these problems, but a general upskilling of all participants is needed.

Further ways to improve quality

The question of building quality has a myriad of contributing factors. Other areas of design and construction improvement could be considered to improve the quality of our existing residential upgrades and new builds:

  • Focusing on educating clients – teaching the potential quality risks and ramifications of various aspects of their budget and brief such as multiple cladding materials, complex details and features.
  • Making an extended range of building information more easily available and free. Extending the scope of Acceptable Solution details available – for example, E2/AS1 to include timber fenestration and to cover the increased breadth of construction situations that now arise.
  • Improving the current Licensed Building Practitioners Scheme, such as increasing the minimum skill level requirements.

Joining design and construction

When I started work as an architect in the late 80s, there were still many active remnants of the old traditional model of building construction, from design through to construction. The connection between these two steps was stronger, too, especially with the presence of a clerk of works on site, and I look back almost fondly at the way they helped bridge that gap.

Now most designers and many architects usually undertake design and documentation only through to the building consent stage. Traditionally, it was rare to take on projects without providing full service through to practical completion and post-occupancy. That continuity was priceless.

Having the architect present or always available during construction meant the person who designed the details of the building could discuss any issues with the clerk of works or the subcontractor involved in situ. Details could be discussed and substituted or amended to suit the real situation in front of them, and many potential future building quality issues were nipped in the bud.

In my experience, these discussions were open, respectful and honest two-way dialogues bringing together the usually vast specific experience of the tradesperson with the theoretical and design objectives of the architect. These discussions could never take place at every step of the design process, but they could occur before any contentious aspect or detail of the project was actually built.

Finally, one point in the construction quality research was obvious. Self-certifying subtrades such as electricians and gasfitters are less represented in the construction inspection failure statistics. Maybe part of the answer lies in that model!

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