(Build It) Right First Time
The title of this 1979 Th’ Dudes song could be a mantra for the residential construction industry. Homeowners invest significant time and money and expect, as a minimum, a house that keeps the 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 now between 10 and 30 years old and therefore not built in accordance with the current Acceptable Solutions.
Seven most common weathertightness failures
To illustrate these failures, we have kept words to a minimum and used photos and accompanying text from building assessors’ 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 (see Figure 1).
Kick-out flashings at wall and roof junctions
The absence of a kick-out flashing allows water to flow behind the cladding (see Figure 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 (see Figure 3).
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 (see Figure 4).
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 (see Figure 5).
Joinery installation
Head, jamb and sill flashings fail to deflect water to the exterior or are non-existent (see Figure 6).
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 (see Figure 7).
The leaky home crisis has given us 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 been updated to help manage the problem. Nevertheless, we must remind ourselves to learn from the past and (Build it) Right First Time.
Quiz:
1. The Weathertight Services Technical Team is part of which organisation?
a. Ministry of Business, Innovation and Employment (MBIE).
b. BRANZ.
c. Th’ Dudes.
d. MetService weather forecasting.
2. How old are most of the buildings where weathertightness failures have been found?
a. 2 years.
b. Between 5 and 10 years.
c. Between 10 and 30 years.
d. 30 years or older.
3. Which of the following are common areas for weathertightness failure?
a. Thresholds to decks.
b. Joints and flashings in claddings.
c. Exterior joinery installation.
d. Poor ground clearances.
e. All of the above.
Answers: 1.a, 2.c, 3.e.
Note
All photos courtesy of Frank Wiemann, NZIBS.
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Articles are correct at the time of publication but may have since become outdated.