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Could my house be a leaker?

Reduced Risk

Protection of wall cladding by roof eaves, the wider the better.

Drained and ventilated cavity behind cladding, e.g. brick veneer.

Traditional and simple designs.

Separation of cladding from ground, paving and tiled surfaces.

Traditional boron treated timber framing.

Increased Risk

No roof eave protection of walls.

Exposed sites.

More complex designs, i.e. lots of junctions and corners.

Monolithic claddings, e.g. stucco plaster, fibre cement, etc.

Tiled balconies and ‘solid’ handrails.

Highest Risk

Chemical free (untreated), H1-LOSP and Douglas fir timber framing, in combination with any current monolithic cladding system.

What is the problem?

All buildings will leak to some degree, either from imperfections in the design and construction, or subsequent actions such as adding an
outside light or TV aerial, or raising garden levels too high.

Moisture can be retained behind the cladding by not being able to drain and dry out.

This moisture is hidden, usually on the back of the cladding so the owner or occupant can be quite unaware.

Retained moisture can lead to mould growth on building materials, decay of timber framing and rusting of steel fixings and framing.

With timber not treated against decay, the chance of decay occurring is very high. The nature of some of these decays is of great concern, e.g. dry rot.

What can I do about it?

If you have an existing home

Seek professional advice.

Call our team of professionals at Prendos on 09 486 1973 or email us at [email protected]

Refer to the Building Research Association of New Zealand and the New Zealand Institute of Building Surveyors – see our Useful Links page.

If your home is being built or to be built

Check and provide weatherproof details. Refer to the Related Articles, BRANZ and your cladding supplier.

Use roof eaves wherever possible

Install cladding over a ventilated and drained cavity, refer cladding manufacturer for details

Use H1.2 (pink or blue) or H3 (green) framing. Note; H1.1 contains an insecticide only).

Use H3 where the risks of water leakage are higher, such as balconies.

If the frame is already in place and untreated, seek advice for site applied chemical treatment; refer to timber treatment suppliers and check with Council.


When did the building industry start using untreated framing timber?

NZS 3602, the Standard which permitted the use of kiln dried untreated pine was published in September 1995. The use of untreated timber would have started from 1996 onwards. Douglas fir has always been allowed without any treatment, however it is more durable than untreated kiln dried pine.

Why did the industry change to untreated framing timber?

The only treatment requirement was for insect attack. After a field study, it was considered that kiln dried timber was unpalatable to borer. Issues of water ingress and fungal decay were not considered.

What do they mean by ‘treated framing timber’?

‘Treated timber’ means the addition of a chemical to prevent insect attack. Traditional wet framing used Boron which is an insecticide with the additional effect of also being an effective fungicide. Its
presence certainly prevents a high incidence of early decay, especially dry rots. NZS3602 has been revised. This allows untreated pine for dry situations, H1.1 for insect risk, H1.2 (pink or blue)? for exterior framing including subfloors and H3 (H3.1 or H3.2) for balconies.

 

If my house was built using untreated framing timber, how long might it take for problems to be evidenced?

This is unknown. The low moisture levels that can cause certain decays mean it could take many years for the problem to surface. However, significant decay is being found in buildings built less than one year ago. Some decay has also been found in buildings being constructed.

If my house was built using untreated framing timber will I have problems?

It all depends on how much moisture penetrates and accumulates behind the cladding. The biggest safety factor is the roof eave – the wider the better. However, any moisture entry is of great concern and there is no protection against decay.

If I know I have got problems and sell my house, is this legal?

Take advice from your own solicitor.

If my house leaks and rots will my insurance cover this?

You need to look at your insurance policy. Most insurance policies do not cover gradual damage, though each policy is different. Take advice from your solicitor.

What else can I do?

Try to bring the parties involved in the construction to account. Unfortunately this may mean expensive legal action. If those involved will not assist, money should first be spent on doing the repair and then you should try to recover costs.

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