Concrete masonry and weathertightness
The Acceptable Solution for weathertightness E2/AS1 is a solution for claddings on timber frame structures and is not applicable to other nonframed structural systems such as concrete masonry.
This information was confirmed as current in February 2016. It originally appeared in Codewords newsletters prior to January 2014.
NZS 4229:1999 Concrete Masonry Buildings not Requiring Specific Design is cited under the Acceptable Solutions for Clause B1 Structure of the New Zealand Building Code. Although NZS 4229, Clause 2.3 outlines surface coatings for waterproofing of concrete masonry, the Standard is not cited as an Acceptable Solution for weathertightness under the Acceptable Solutions for Building Code Clause E2.
Designers must therefore satisfy themselves of the adequacy of surface coatings for weathertightness and present the solution for acceptance by the building consent authority. It is worth noting that, ordinarily, coatings are designed to prevent moisture from being absorbed through the surface of the blockwork. Where the masonry design might be subject to unusual microcracking at block joints, either a surface coating with the capacity to bridge these joints must be used, or other provisions put in place to accommodate the movement.
NZS 4229 does offer some guidance as to surface coatings that have been considered adequate by a Standards committee, but these nevertheless remain as alternative solutions, and outside the Acceptable Solutions and Verification Methods for automatic acceptance by BCAs.
Designers must also consider other weathertightness issues such as joints around openings, building junctions and movement control joints, which will require special weathertightness considerations and must be included in the documentation with applications for building consents.
Maintenance and durability
While structural requirements for the durability of concrete masonry are for not less than 50 years, the waterproof coatings are required to last a minimum of 15 years under Clause B2(b)ii... where failure could be detected during normal maintenance.
While it is necessary for protective coatings to perform for the life of the building, individual coatings are not required to do so. It is the building owner's responsibility to ensure that the building continues to comply with the Building Code, and this places the responsibility on them for continuing maintenance or replacement, in this case, of the surface coatings.
Code compliance certificates
Under the Building Act 2004, code compliance certificates will be issued on the basis that work complies with the consent documents. It is therefore essential for designers to have the details for weathertightness included in the building consent documents, and notify the consent authority of variations that may be made throughout the passage of the work.