Issue 52 – August 2013
Mortar for brick veneer must achieve a 7-day masonry to mortar bond strength of 200 kPa when tested in accordance with AS 3700:2011 Masonry structures Appendix D. Compressive strength at 28 days when tested to NZS 4210:2001 Masonry construction: Materials and workmanship must be not less than 12.5 MPa.
Mortar is typically supplied as a dry premix of accurately measured sand, cement, and additives to which the prescribed amount of water (as shown on the packaging) is added on site. The advantages of using the premixed material is accuracy and cleanliness of the dry constituents.
Mortar may also be mixed on site (in maximum batches of 0.3 m3) in the following ratios (from Table 2.1 of NZS 4210).
- Exposure zones D and E in a ratio of 1:0–025:3 cement:hydrated lime:mortar sand.
- Exposure zones B and C in a ratio of 1:0.5:4.5 cement:hydrated lime:mortar sand.
The drawbacks of mixing mortar on site include keeping the sand clean plus ensuring consistency and accuracy of the mix proportions.
Section 3.15 of the BRANZ Good Practice Guide: Masonry Veneer covers the mixing requirements for mortar.
Summarised from BRANZ Guideline, August 2013.