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Advancement in Combating Leaky Building Problem

Media Release

23 June 2004


Weathertightness Solution - Significant Advancement in Combating Leaky Building Problem

The Building Industry Authority (BIA) has released new requirements that define good practice for the way buildings are designed and built to help overcome leaky building problems.

‘The changes are aimed at achieving better buildings for New Zealanders,’ chairman Barry Brown said.

‘They’re aimed at providing better protection against leaks for building owners and users and they represent the best New Zealand and international thinking in building science.

‘Together with the recent changes to treated timber requirements, we have now addressed many of the underlying technical causes of leaky buildings problems. The Building Bill now before Parliament will also provide a range of measures to improve building performance for owners and users.’

The new requirements, or Weathertightness Solution, contain much more detail and guidance for architects, builders and building inspectors on how buildings should be designed and built to prevent leaks or to manage them if they occur.

Important Elements of the New Requirements

The BIA is changing its Acceptable Solution (technically called E2/AS1 but sometimes referred to as the ‘Weathertightness Solution’) for the way buildings manage external moisture (weathertightness).

An underlying philosophy of the changes is the adoption of the ‘4Ds’ principles of water management in buildings.

The 4Ds (in order of importance) are:

Deflection – that is keeping rain away from sensitive areas by using features like eaves or flashings.

Drainage – providing ‘paths’ for water that gets behind cladding to drain away. Drained cavities are an example of this.

Drying – removing water that leaks through a cladding and does not drain away – principally through ventilation.

Durability – making sure materials used to construct walls and roofs have an appropriate level of durability for the situation they will be used in.

The changes will apply to timber framed buildings up to three storeys or 10 metres high (this includes most standard houses and low rise apartment buildings). Key elements of the change are:

- The introduction of a risk management approach to weathertightness protection. That is, the more at risk a building is of leaking (based on a range of factors like complexity of design and exposure to wind), the greater the protection required to stop water getting in.
- Much more detail around the design of water protection features like flashings and cappings for parapets.
- The inclusion of more cladding types than under the old requirements.
- The need for drained cavities in a wider range of building situations.
- More detail around designing problematic areas like decks, balustrades and balconies.

The BIA has also introduced a testing method to allow cladding manufacturers to prove the weathertightness performance of their products when used as part of an overall cladding system that includes a cavity.

Timing of Changes

The BIA has announced a staged implementation of the changes:

- The changes will apply to projects where consents are applied for from 1 February 2005 – this gives time for councils and the industry to have any operational changes needed in place

- People who have received consents prior to 1 February 2005 under the existing Acceptable Solution have until 31 January 2006 to finish their building work and obtain a code compliance certificate.

These dates are subject to final feedback from the sector to ensure there are no significant unforeseen operational issues that would make the 1 February 2005 implementation impractical.

Impact of Changes

The New Zealand Institute of Economic Research undertook a cost/benefit study of the changes for the BIA.

This showed the impact would vary according to the type of building involved. They estimated additional costs for a simple brick house would be minimal – around $500. However, for a non-brick house requiring a drained cavity and the new flashing details, the cost could be $5,000 or greater depending on size. The average cost increase over all new houses is around $2,500.

The additional cost for apartments will also vary, but the average cost increase over all new apartments was estimated to be $3,000.

Mr Brown said the Authority had considered these implications very carefully when deciding on the changes and that they have been subject to rigorous consultation and peer review.

‘Ultimately though, they are a relatively small cost when considered over the life of a building and against the tens of thousands of dollars required for fixing leaky building problems – not to mention the emotional cost involved.’

The study showed a net benefit of $800 million would result from the changes over the next 25 years, largely as a result of not having to repair leaky buildings.

Mr Brown also said people involved in the building industry – manufacturers, architects, builders, and building inspectors – would need to do things differently as a result of the changes and this would lead to better building outcomes.

‘Many in the industry will welcome these changes, and we have had significant industry input into determining them.

‘Our key message to the industry is that these changes are aimed at achieving better buildings for New Zealanders – and that is in the interests of everybody.

‘We also want to assure the industry we are fully committed to working with them to implement these changes.’

ENDS


Explanation of Acceptable Solutions

The BIA is changing the Acceptable Solution for Clause E2 of the Building Code (technically known as E2/AS1). This clause covers the way buildings should be built to provide adequate resistance to the penetration and accumulation of moisture from the outside.

Acceptable Solutions provide a prescriptive means of complying with the Building Code. They set out a building method, which, if followed, means a building is automatically deemed to comply with the relevant part of the Building Code.

Acceptable Solutions are not mandatory.

A building can be designed and constructed in a way that differs partially or totally from an Acceptable Solution but can still comply with the Building Code. This is known as an Alternative Solution and must be considered on its merits on a case-by-case basis by a council or building certifier when determining code compliance.

Background to Weathertightness Solution


What is being changed?

1. The BIA is changing the Acceptable Solution for Clause E2 External Moisture of the Building Code (known as E2/AS1 and sometimes called the “Weathertightness Solution”).

This clause covers the way buildings should be built to provide adequate resistance to the penetration and accumulation of moisture from the outside.

2. It is also introducing a testing method to allow cladding manufacturers to prove the weathertightness performance of their products when used with a cavity as part of an overall cladding system. (This is a Verification Method called E2/VM1)


The Building Code and Approved Documents

The Building Code consists of 35 clauses. Each clause sets out performance standards that buildings must meet. These cover things like durability, fire safety, energy efficiency and access.

Approved Documents provide a prescriptive means of complying with the clauses of the Building Code. That is, buildings built to the method described in an Approved Document are automatically deemed to comply with the Code – they’re sometimes referred to as “cook book” solutions because they prescribe a “recipe” for ensuring compliance.

The BIA publishes two types of Approved Documents - Acceptable Solutions and Verification Methods.

Acceptable Solutions prescribe certain construction methods (e.g. what insulation is needed to comply with energy efficiency requirements or what level of treatment is required for timber to meet the durability requirements).

Verification Methods set out mathematical calculations, scientific tests or measurement methods to determine compliance (e.g. calculations for the size of beams).

Are Approved Documents mandatory?

No – they provide one means, if followed, of ensuring compliance with the Building Code.

A building can be designed and constructed in a way that differs partially or totally from an Approved Document but can still comply with the code. This is known as an Alternative Solution and must be considered on its merits by a council or building certifier when considering code compliance. They must be satisfied on reasonable grounds that the building complies with the Building Code in order to issue a building consent or code compliance certificate.


What are the changes?

The most substantive changes are to the Acceptable Solution.

The new Acceptable Solution provides considerably more detail about the way buildings should be designed and constructed to achieve weathertightness. In simple terms, the old Acceptable Solution was only 12 pages long. The new Acceptable Solution has around 150 pages of detail.

Important areas of change are:
- The introduction of a risk matrix – to help determine the level of weathertightness risk for a particular design and to guide the way that risk should be managed
- A wider range of cladding systems are covered

Claddings covered in old solution Claddings covered in new solution

Wall Claddings
- Brick veneer
- Timber weatherboards
- Stucco Wall Claddings
- Brick veneer
- Stucco
- Timber weatherboards
- Fibre cement weatherboards
- Profiled metal
- Fibre cement sheet
- Plywood sheet
- EIFS

Roof Claddings
- Butyl/EPDM membranes
- Concrete/clay tiles
- Pressed metal tiles
- Profiled metal

- It sets out a method of constructing drained cavities, to allow water that penetrates claddings to drain
- It specifies methods for installing certain types of window to minimise the risk of leaks
- It sets out methods for waterproofing certain types of solid decks and for building timber slatted decks
- It provides clear direction on how the junctions of roofs and walls should be designed
- It provides detail on designing and installing flashings
- Specific training is required for people to install certain types of wall or roof claddings.


Will these changes fix the weathertightness problem?

They are a major part of resolving the weathertightness problem, but only part of the answer.

It’s generally accepted that there are a large number of factors that contributed to the problem like design and building standards; the need for councils to improve their consenting and inspection processes and trends toward “riskier” building types.

The changes in the Weathertightness Acceptable Solution are very important, but they are part of a wider Government and building industry response. In particular, the recent changes around treated timber requirements and the measures in the Building Bill currently before Parliament are also part of the response.

How did the BIA decide on these changes?

When developing changes to the Building Code or its Approved Documents the BIA consults widely, reviews existing research and undertakes independent analysis and research: In this case this involved:
i. Initial discussion with industry stakeholders on options.
ii. Publication of a consultation document containing options for proposed changes to the Acceptable Solution.
iii. Publication of an independent cost benefit analysis (prepared by NZIER) of the proposals and a regulatory impact statement.
iv. An eight week consultation period that allowed submissions on the proposal, the cost benefit analysis and the regulatory impact statement to be made. In total, 225 submissions containing several thousand pages of comments were received.
v. Submissions were then analysed by BIA staff and a BIA facilitated working group. The working group included a cross section of representatives from the timber and building industry. Further work on refining the changes was undertaken over a period of months.
vi. The Building Industry Authority considered recommendations from this process and made final decisions on the changes.
vii. Final decisions on the timing for implementing these changes will be made following final industry feedback.

How does this relate to the recent treated timber changes?

The two are closely linked.

The BIA recently introduced a new Acceptable Solution for treated timber. This introduced a requirement for increased levels of treatment for timber used in parts of buildings more at risk of damage if leaking occurred.

The Weathertightness Solution is about enhancing the ability of a building to keep water out in the first instance, and then providing methods for managing water that does penetrate the cladding of a building. The timber treatment changes are about increasing a building’s ability to cope if it does leak by ensuring the timber framing has an appropriate level of durability.

Combined, they significantly reduce the risk of leaking and deterioration for buildings that follow the requirements.


What do the changes mean in terms of the cost to homeowners?

The New Zealand Institute of Economic Research undertook a cost/benefit study of the changes for the BIA.

This showed the impact would vary according to the type of building involved. They estimated additional costs for a simple brick house would be minimal - around $500. However, for a non-brick house requiring a drained cavity and the new flashing details the cost could be $5,000 or greater depending on size. The average cost increase over all new houses is around $2,500.

The additional cost for apartments will also vary, but the average cost increase over all new apartments was estimated to be $3,000.

When do the changes come into effect?

The changes come into effect for new consents applied for on or after 1 February 2005.

People building under the existing acceptable solution have until 31 January 2006 to finish work and obtain a code compliance certificate.

However, we strongly encourage people planning building projects now to take the new requirements into consideration as they do represent best current thinking on achieving weathertightness.

These dates are subject to final feedback from the sector by 31 July to ensure there are no significant unforeseen operational issues that would make the 1 February 2005 implementation impractical.

How do these changes affect buildings already under way?

The BIA is introducing implementation dates so that current building projects are not affected by these changes

If a building has been consented under the existing Acceptable Solution, its owners have until 31 January 2006 to finish it and obtain a code compliance certificate.

If the building received a building consent as an Alternative Solution then code compliance certificates and building certificates should be issued where the council or private building certifier (acting within their scope of approval) is satisfied on reasonable grounds the Alternative Solution complies with the Building Code. Councils and private building certifiers must consider each building on its merits.

The new E2/AS1 is not the standard for assessing Alternative Solutions. Councils and private building certifiers must consider each building on its merits.

ENDS

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