Respondents will frequently argue that the claimants have failed to mitigate their loss by not undertaking repair work in a timely manner. The issue to be decided is whether the claimant has acted reasonably.

A claimant is only required to act reasonably. Whether he/she has done so is a question of fact in the circumstances of each particular case. He/she must however act not only in his/her own interests but also in the interests of the respondents and to keep down the damages so far as it is reasonable and proper by acting reasonably in the matter. One test of reasonableness is whether a prudent person would have acted in the same way.

Obviously, "reasonableness" is an all-important factor to take into consideration directly linking to the interests of the respondent/s. A flexible but fair approach is thereby called for. Claimants should not necessarily be expected to have chosen the cheapest option, but equally if the cost is excessive, then the amount awarded could be cut back.

For cases on mitigation of loss see:

• DBH 01276: The adjudicator held that the claimants did not mitigate their losses because it was found that the claimants virtually watched their house slowly deteriorate before them, and did not take reasonable steps to protect their investment. The High Court upheld that finding
• DBH 00119: the Council argued that because the claimants did not fix the house, they therefore allowed matters to get worse and so did not mitigate their loss. The adjudicator denied the Council's arguments in saying that had the claimants carried out the remedial work their claim would have been for a much greater amount in damages than what they were currently claiming for.

At times respondents allege contributory negligence on the part of the claimants. The situations that may give rise to this include:

• The claimants failing to take all reasonable steps to check out a property although they knew, or ought reasonably to have known, of the risks associated with monolithic-clad houses.
• Where the claimant has supervised the building work and, for example, used labour-only builders
• Where the claimant has contributed to the weathertightness issues by their actions or inaction.

Section 3 of the Contributory Negligence Act 1947 also allows for apportionment of responsibility for the damage where there is fault on both sides or fault on the part of the claimant and other parties. Fault is defined in s2 as meaning:

"..negligence, breach of statutory duty, or other act or omission which gives rise to a liability in tort or would, apart from this Act, give rise to the defence of contributory negligence."

The current approach to contributory negligence is set out in Dairy Containers Ltd v NZI Bank Ltd. That case confirms that contributory negligence is a failure on the part of the claimant to take reasonable care to protect his or her own interests when they are, or ought to have been, known to the plaintiff and reasonably foreseeable.

There is also a lengthy discussion on contributory negligence in the Auckland High Court's in Hartley v Balemi. Justice Stevens stated that the question of fault needed to be decided objectively and required the claimant to exercise such precautions as would someone of ordinary prudence. He noted that the only time a more subjective test had been used by the courts was to place a less demanding standard of care on the claimant due to their personal circumstances.

Often respondents raise contributory negligence as a defence where the claimant has purchased the property knowing that it was a leaky home. In such cases the purchase price has usually been reduced because of the condition of the property. It is probably a moot point in such cases as to whether the remedial costs are reduced due to contributory negligence or whether in assessing damages the amount ordered is reduced as the loss suffered by the claimant is less than the level of the damages.

Other examples of cases where the issue regarding contributory negligence was raised include:

• DBH 00119: the adjudicator held that the claimants contributed to their own loss as both claimants had experience in the construction industry and should have been alerted to the possible problems. The damages that were awarded to them were therefore reduced by 33 per cent
• DBH 02368: A failure to obtain a pre-purchase report led to a finding of contributory negligence.
• DBH 02368: Contributory negligence was assessed at 50 per cent.

When dealing with a claim for damage, after deciding liability (responsibility for the damage) and quantum (the amount) the Tribunal must consider whether the repair work will do more than restore the property to the condition that it would have been in if it had not been a leaky home. For example if through normal fair wear and tear the property would have required maintenance or a repaint anyway even if there had not been any weathertightness issues then the cost for such maintenance or a repaint may be reduced in deciding the amount respondents should pay.

In other words if the repairs or remedial work make the property "better" than before, it may be necessary to reduce the damage award in order to take "betterment" into account, which is similar to taking depreciation into account.

For cases on betterment and depreciation look at:

• DBH 00626: The adjudicator concluded that there will be an element of betterment when the remedial work is carried out and so the value of the betterment was set at 50% of the value.
• DBH 01917, 01514, 02368: These are all cases where damages were reduced based on betterment. See also Ponsonby Gardens Determinations - DBH 00062, 00104, 00136 and 00932

Even though a claim has been found eligible, all or part of the claim may not be successful because the limitation period for that particular claim has expired. These limitation defences can be raised where the claim has been found eligible as different limitation periods can apply to different types of claims. Whilst eligibility is based on 10 years from when the house is built, the date in which the house was built may not be the relevant date from which the time period starts. See WHT 30/07 whereby the Chair of the Weathertight Homes Tribunal removed all the respondents to a claim based on the arguments surrounding limitation periods.

The main limitation periods that apply to WHT claims include:

• Section 14 of WHRSA 2006 provides that for a claim to be valid the dwellinghouse must be built within a period of 10 years immediately before the day on which the claim is brought. A person brings a claim by applying for an assessor's report under section 9.
• For claims of negligence the limitation period is 6 years from the time of the negligent actions (s4 Limitation Act). However, if it is a latent defect as is often the case with leaky buildings the time begins to run when the claimant discovers, or ought with reasonable diligence to have discovered the defective state of the property (Invercargill City Council v Hamlin).
• In contract, the time period must be within six years of the date of the breach of the contract - section 4 Limitation Act 1950. This is subject to an extension for disability, acknowledgement and part payment or fraud and mistake as set out in sections 24-28 of the Limitation Act.
• Section 91(2) Building Act 1991 & section 393 Building Act 2004 prohibits civil proceedings arising from building construction 10 years after the date of the act or omission on which the proceedings are based. This is the "long stop" period - ie, even if it is not statute barred in tort (discoverability test) a claim could be barred under the Building Act.

For cases on Limitation periods see:

• DBH 01917: a designer succeeded in his limitation defence on the basis that both the Building Act 1991 and 2004 state that civil proceedings cannot be brought against a person 10 years or more after the date of the relevant act or omission. It was found that the designer had no involvement in the construction of the house after completing the drawings and specifications in September 1993, whereas the claim had been filed in November 2003.
• DBH 02601: The adjudicator accepted the argument that some of the claims in that matter were "statute-barred" pursuant to section 4 of the Limitation Act 1950. That was because the work carried out under the contract and/or the date of discovery of the defects for tortious purposes was outside the 6-year limitation period.
• DBH 00376: The vendors succeeded in arguing that a claim for breach of contract against them was time-barred.
• DBH 02442 (Procedural Order No. 11 regarding a Strike Out Application): A respondent argued that the claim made against him was "statute-barred" because his involvement in the construction of the house fell outside the 10-year timeframe. The adjudicator was obliged to follow Cromwell Plumbing Drainage & Services Ltd v de Geest Brothers Construction Ltd, whereby the High Court held that a claim for contribution is not subject to the Limitation Provisions. The adjudicator's decision was upheld in the High Court in Dustin v Weathertight Homes Resolution Service because Justice Courtney held that the adjudicator was bound by the decisions of superior courts. Consequently in terms of contribution, others may be joined as a party to the claim, regardless of whether their actions fall outside the 10-year timeframe.