(Build It) Right First Time

By - , Build 185

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.

Figure 3: Stucco plaster cladding and joinery close to a tiled deck. Joinery installation issues at the jamb. Minimal threshold separation allows water uptake into the uncoated, porous bottom edge of the stucco plaster and creates maintenance difficulties (bottom photo).
Figure 1: Butyl rubber membrane over a small roof. Inadequate front edge installation with the corner cut exposing the plywood substrate.
Figure 2: No kick-out or diverter provision at the bottom end of the apron junction to a fibre-cement cladding (top photo). Destructive testing confirms water ingress and timber damage (bottom photo).
Figure 4: Top-fixed stainless-steel handrail penetrates an EIFS-clad parapet (top photo). There are clear signs of water ingress around the penetration point with the coating cracks indicating moisture movement to the underlying timber framing. The steel bracket-fixed timber post directly penetrates the cladding (bottom photo). This cannot be made weathertight or adequately maintained.
Figure 5: Stucco plaster cladding over rigid backing. Incorrect control joint formation, without separation of mesh and plaster over the joint, leading to movement cracking and water ingress.
Figure 6: Texture-coated fibre-cement cladding. Window head flashings have no stop-ends or other means of preventing water ingress. Coating and cladding sheets are in contact with the shoulder of the flashing, which allows water uptake to the cladding edges by capillary action. Timber testing reveals visible water staining and a very high moisture reading (bottom photo). There is also no evidence of proprietary waterproofing systems installation to the window perimeter.
Figure 7: A fibre-cement-clad timber-framed column and built-up paving resulting in significant damage.

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).

Figure 1: Butyl rubber membrane over a small roof. Inadequate front edge installation with the corner cut exposing the plywood substrate.

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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).

Figure 2: No kick-out or diverter provision at the bottom end of the apron junction to a fibre-cement cladding (top photo). Destructive testing confirms water ingress and timber damage (bottom photo).

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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).

Figure 3: Stucco plaster cladding and joinery close to a tiled deck. Joinery installation issues at the jamb. Minimal threshold separation allows water uptake into the uncoated, porous bottom edge of the stucco plaster and creates maintenance difficulties (bottom photo).

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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.

Figure 4: Top-fixed stainless-steel handrail penetrates an EIFS-clad parapet (top photo). There are clear signs of water ingress around the penetration point with the coating cracks indicating moisture movement to the underlying timber framing. The steel bracket-fixed timber post directly penetrates the cladding (bottom photo). This cannot be made weathertight or adequately maintained.

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Joints and flashings in cladding

These are often inadequate allowing water ingress and damage particularly at horizontal and control joints (see Figure 5).

Figure 5: Stucco plaster cladding over rigid backing. Incorrect control joint formation, without separation of mesh and plaster over the joint, leading to movement cracking and water ingress.

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Joinery installation

Head, jamb and sill flashings fail to deflect water to the exterior or are non-existent (see Figure 6).

Figure 6: Texture-coated fibre-cement cladding. Window head flashings have no stop-ends or other means of preventing water ingress. Coating and cladding sheets are in contact with the shoulder of the flashing, which allows water uptake to the cladding edges by capillary action. Timber testing reveals visible water staining and a very high moisture reading (bottom photo). There is also no evidence of proprietary waterproofing systems installation to the window perimeter.

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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).

Figure 7: A fibre-cement-clad timber-framed column and built-up paving resulting in significant damage.

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.

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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.

Figure 3: Stucco plaster cladding and joinery close to a tiled deck. Joinery installation issues at the jamb. Minimal threshold separation allows water uptake into the uncoated, porous bottom edge of the stucco plaster and creates maintenance difficulties (bottom photo).
Figure 1: Butyl rubber membrane over a small roof. Inadequate front edge installation with the corner cut exposing the plywood substrate.
Figure 2: No kick-out or diverter provision at the bottom end of the apron junction to a fibre-cement cladding (top photo). Destructive testing confirms water ingress and timber damage (bottom photo).
Figure 4: Top-fixed stainless-steel handrail penetrates an EIFS-clad parapet (top photo). There are clear signs of water ingress around the penetration point with the coating cracks indicating moisture movement to the underlying timber framing. The steel bracket-fixed timber post directly penetrates the cladding (bottom photo). This cannot be made weathertight or adequately maintained.
Figure 5: Stucco plaster cladding over rigid backing. Incorrect control joint formation, without separation of mesh and plaster over the joint, leading to movement cracking and water ingress.
Figure 6: Texture-coated fibre-cement cladding. Window head flashings have no stop-ends or other means of preventing water ingress. Coating and cladding sheets are in contact with the shoulder of the flashing, which allows water uptake to the cladding edges by capillary action. Timber testing reveals visible water staining and a very high moisture reading (bottom photo). There is also no evidence of proprietary waterproofing systems installation to the window perimeter.
Figure 7: A fibre-cement-clad timber-framed column and built-up paving resulting in significant damage.

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