(BUILD IT) RIGHT FIRST TIME

The title of 1979 Th’ Dudes classic should be a mantra for the residential construction industry

Every year homeowners spend significant amounts of time and money on house construction. They expect, as a minimum, a building that keeps water out long-term.

The work of MBIE’s Weathertight Services Technical Team puts us in a good position to identify recurring areas of weathertightness failures. It is worth noting that most of these failures are for buildings between 10 and 30 years old and therefore not built in accordance with the current Acceptable Solutions of the New Zealand Building Code.

Here are seven of the most common problems. To illustrate these failures, we have kept our words to a minimum, instead using photos and accompanying text from a building assessor’s reports.

Membrane roofs/gutters, scuppers and decks

These commonly show failures at joints, adherence to other materials or at upturns and downturns of membrane sheets.

 

1.Kick-out flashings at wall and roof junctions
The absence of a kick-out flashing allows water to flow behind the cladding.

2. Thresholds to decks
The junctions between the walls, joinery, balustrades and decks are prone to water ingress due to inadequate threshold heights, folds and corners or cladding proximity to membranes.

Parapets, balustrades and attachment points

Water entry can cause structural damage to parapets and solid balustrades at either capping or gutter and deck levels due to lack of saddle-flashings, cross fall, expansion joints and plan change direction. Damage to structure can also occur where open balustrades are fixed through membranes, solid balustrades, and walls.

Joints and flashings in cladding

These are often inadequate allowing water ingress and damage particularly at horizontal and control joints.

Joinery installation

Head, jamb and sill flashings fail to deflect water to the exterior or are non-existent.

Ground clearances

Unpaved and paved ground levels are too high, failing to protect either cladding or framing. This requires particular care at garage door openings where driveways are close to floor level for ease of vehicle entry.

The leaky home crisis has given us all a greater understanding of how moisture enters and damages a building. Fortunately, we can now build to prevent, minimise and manage water ingress and egress, enhancing the building’s life and providing homes that are healthy.

Legislation, building practices and controls have, and are being, updated to help manage the problem. MBIE’s Building Code Update 2021 consultation document proposes options for raising performance standards. At a conservative estimate, this could bring New Zealand’s Code up to comparable international standards, or boldly, above these standards, leading the way whilst simultaneously meeting our energy efficiency and wider climate-change obligations.

 

Regardless, we must remind ourselves to learn from the past and (build it) right first time.

 

This article is an excerpt from Codewords Issue 102. Reading Codewords articles that are relevant to your licence class is a mandatory requirement for Licensed Building Practitioners. These questions can be answered through the LBP portal, online on the Under Construction website or recorded on the magazine, then provided at the time of renewal.