DOIA 1617?0515 5 DEC 2018 Mr Matt Taylor By email: matt@matthewtaylor.co.nz Dear Mr Taylor Thank you for your email of 21 October 2016, requesting the following information under the Official Information Act 1982 (the Act): the briefing dated on or around 29 May 2013 from Mike Stannard to the Minister of Housing Nick . Smith on a reduced standard of foundation repairs for earthquake-damaged properties in Canterbury. Enclosed is a copy of the briefing you have requested. Some information has been withheld under section of the Act. Where information has been withheld for section 9 reasons, in terms of the Act, lam satisfied that, in the circumstances, the decision to withhold this information is not outweighed by other considerations that render it desirable to make the information available in the public interest. You have the right under section 28(3) of the Act to request a review by the Ombudsman. The relevant details are: The Ombudsman Office of the Ombudsman PO Box 10 162 Wellington 0800 802 602 You ssincer ly Mike Stannard Chief Engineer Building System Performance its . a .41 Ministry of Business, I. - .e?i lnnovation&Employment Minister of Housing cc Minister for Building and Construction Date 29 May 2013 Ministry reference 432 12?13 Building Code requirements for house foundation repair and rebui @arios in Canterbury Purpose A A 7% a?meeti Id W0 This briefing is in response to questions you posed to April 2013. Key Points \2 . 1 gigou met with Adrian Regn?ault, Gene ger i Performance, and . Lisiness, innovation and 0 Employment (the Minist 2013. 2? You requested adv' . i 7 1 the stan . . ort - uilding of foundations in Canterbury for hou - ategory (TCsta could be applied for older properties nearing the eir This question was particularly in the context of 5 I sing orporation property repairs. 3 The Mini a; de I ?>?b?kground information on the guidance issued by the Ministry post-Canterbury earthquakes, attached as Appendi?x 1, and examples of the standard required for the repair of foundations in Canterbury for houses categorised as TC-3, attached as Appendix 2. Recommendations 1 Note this briefing is for your information. Relevant General Manager Adrian Regnault, General Manager Building System Performancesg?zxa) Principal author In Confidence Building" Code requirements for house foundation repair and rebuild scenarios in Canterbury Context 4 Yoqgmet with Adrian Regnault. General Manager Building System Performance, from the Ministry 'on 10 April 2013 5 You requested advice on: 1 the standard required for the repair or rebuilding of fou? Cant for houses categorised as Technical Category (T and What is) red a. rebuild and What is a amaged during the Canterbury Where does the boundary ?45? A considered a repair re . earthquake seq?uen Context (Q repaired foundation was required to perform house foundation, then the costs and timeframe for yet cessive, particularly in T03. this with the earthquake?prone building requirements for existing . buildings, where the buildings are required to be strengthened to at 3% of New Building Standard but not to the full 100%. - ?(ou asked if we could be requiring too high a standard and therefore spending too much in Canterbury in comparison with the risks elsewhere in New Zealand, particularly with respect to liquefaction. 7 Ministry response Building Code requirements 9 Under the Building Act 2004 (the Act), all building work must comply with the Building Code. For a new building, this means the whole of the building must be 100% of the current Building Code. When altering or repairing existing buildings, the building work must comply with the relevant provisions of the Building Code and the rest of the building must continUe to perform no worse than before the alteration or repair. 10 For repairs, there is an important distinction between a building and building work. It is only the work actually being carried out that needs to comply with the Building Code. The building as a whole just needs to be no worse than before the repair is carried out. This is the same for foundation repairs. For relevelling foundations or repairing foundation cracks, it is only necessary that the material being used is appropriate for the situation. The foundations as a whole generally just need to perform no worse than before the repair (however, this will depend on the extent of the work being done, and whether it affects the structural integrity of the foundations). 11 The guidance issued by the Ministry encourages repair and releve 'ng where economic and the damage is not excessive. It also takes a rela' inimalist approach for houses with only minor to moderate levels of fou ge a. where minor liquefaction was experienced during the earthq are criteria provided below which no repair is required. gui . ac been to provide cost effective repair methods 'th risks he - in New Zealand. Refer to Appendix 1, Rational issu istry. 12 Repairs will not, in general, improve ce of on. In other words, the repaired foundation wil ull exi standards. This . to 0 u; could be regarded as similar il trengthening to 33% 13 'lf the foundations ar . . -v meet the full?Building Code standard. For we; new. guidance provides three broad . gro nd improvements, or surface structures. Not al a 'o all properties. For new foundations, the es ?r dily able? solutions to be built, rather than taking a ervati Ch of requiring no damage in earthquake events (refer Ap ix 1 a Building Code requirements). I scenarios providing performance requirements andicriteria has and is attached as Appendix 2. @y Foundation performance requirements for older houses \w Is there any concession to. reduce the foundation performance requirements for older houses? This question was particularly in the context of Housing New Zealand Corporation property repairs. - Context 15 You suggested that as the economic life of older buildings being repaired is less than the normal 50 year minimum expected for a new building, it may be justified in considering reduced requirements for repaired or replacement house foundations. Ministry response 16 Where it is not practicable or economic for building work to comply fully with a provision of the Building Code an owner may apply to the council for a waiver or modification of the releVant building code provision. 17 Section 67 of the Act allows the Territorial Authority to grant building consents subject to waivers or modifications of the Building Code. For example, in the context of foundation repairs, an owner such as Housing New Zealand Corporation might request a waiver for the part of Building Code Clause B1 Structure, particularly that part requiring low probability of loss of amenity (refer Appendix 1 Rationale for Building Code requirements). 18 Any waiver or modification would be noted on the consent, kept on the property file and be available to any future buyer so they have the opportunity to un rstand the risk involved. Councils do issue waivers on a regular? basis and istry can provide advice to assist Housing New Zealand Corporation 'senti process. I Supporting documents {15$ - 19 The following documents are attached: WV 0 Appendix 1 Background infor ce by the Ministry post?Canterbury earthqua . - Appendix 2 - Generic Recommendations) 1 Notet' aw rs?rywon- Adrian Re 7 - .. Gene? uilding System Performance pa arios in T03. Hon Dr Nick Smith Minister of Housing Appendix 1: Background information on the guidance issued by the Ministry post= Canterbury earthquakes Rationale for Building Code requirements 20 The Building Code for structure requires consideration of life safety (low probability of rupture during the building life) and amenity (low probability of loss of amenity). To address these engineers design for two limit states defined in @wding Standard (NZS 1170): the Ultimate Limit State, ULS, (a 1 in 500 ye quake); and the Serviceability Limit State, SL8, (a one in 25 year earth 21 A narrow interpretation of SLS may lead to a conclusio th damage and differential settlements should be neg!" The guidance has taken a significantly more en .- 6 "a ure for repairs and rebuilds to be ?readily repai ha :?ncertain'ty about some .43. text the earthquake damage developed. has highlighted so 1.4: ilding Code to repairs of existing buildings. This guidance on repairing and rebuilding houses aff ct I - ,i hqakes. There is also ongoing work to irnprov la nd spec 't Building Code generally. ?d 23 for ce has been to provide greater certainty to ho ers,. esigners, insurers and councils (Building Consent interpret the Actand Code in ,this exceptional situation. Rationale for guidanceissued by the 22 The Canterbury earthqua a regulatory requiremen t? 24 guidance, the general philosophy has been to provide: . nd greater specificity on how to comply with regulatory requirements to inimize ambiguity and disputes between the varioUs parties (eg. engineers acting for homeowners, insurers and building consent authorities, all of whom may have different .objectiVes'), particularly in order to facilitate the building- consenting process 0 pragmatic guidance on criteria for determining whether houses should be repaired or rebuilt, what investigations should be carried out, and a suite of repair and rebuild options for designers that may be appropriate in given circumstances. 25 The approach taken has been to balance the needs of the various parties. These include: homeowners and future oWners, and their need to protect their asset against future events 0 insurers in settling their obligations and considering future underwriting, mindful that insurance contract obligations with homeowners that may be different to regulatory requirements engineers and designers in carrying out their obligations and managing liabilities 0 Building Consent Authorities, to help them make decisions ?on reasonable grounds? for consenting and issuing completion certificates, and builders in carrying out the work. 26 The Ministry has aimed to: 0 have repair and rebuild methods that, where sensible, will provide a degree of improved resilience in future large events while being conscious of any additional cost impositiOn. minimize the need for scarce technical engineering input @ble an concentrate engineering input where the risk is great ampl Technical Category guidance allowed for the repair reb appr' xi i a 80% of Canterbury houses within the Green Zo ee with engineering input. 27 The guidance has been prepared rop ok? - ain on?going seismicity, repeated liquefaction ev a inte . precedented, and lack'of international models . . 4 upon. The prospect of another liquefaction tri :g .: a ry causing further damage roughout the process. 28 :2 nd Building Consent. Authorities to respond to issues as they 'r guidance has been consistently updated as we learn more. On? pment is occurring as new issues are raised and updates are planned Appendix 2: Generic foundation rebuild or repair scenarios in T03 No. Scenario Criteria Foundation Performance requirement 1 Remove existing house and Where superstructure Full Building Code requirements build new house damage and/or (readily repairable in SLS event) foundation damage uneconomic to repair 2 Repair existing house Where foundation Full Building Code requirements superstructure as necessary damage uneconomic to (readily repairable in SL8 event) but completely replace repair. Indicative foundation (lift house off criteria provided on existing foundations) overall stretch of house, crack width and a floor settlement. A A (bk 3? Repair existing house indicatiVe criter? gree( of superstructure as necessary provided on a} for the but replace part of stretch of hou 33' ble to be foundation (demolish part of width . Standard house or lift whole house off settle provided in the foundations as necessary). to improve the ormance of ring beam oundations (additional costs not significantchoice Depending on degree of 66% damage to original house and the extent of the extension. if little damage to existing foundation and extension small, the foundation for the new part may be able to be similar to the existing. Otherwise, to full building code requirements unless Code requirements waivered or modified through due process 5 Repair existing house Indicative criteria Repair must meet building code superstructure as necessary provided on floor (unless waived). Otherwise no but repair/replace corner 0f settlement and slopes. performance improvement over house that for existing foundations 6' Relevel foundations Indicative criteria Generally, no performance provided on floor improvement over that of . settlement and slopes. existing foundations 7' Repair cracks in foundations indicative criteria No performance improvement provided on crack over that of existing foundations widths