Information for all builders, blocklayers and associated trades operating within the South Waikato District area.
This page is intended to explain a few developments that concern builders and masons... the sorts of things that Council's Building Inspectors.
Council's Inspectors have attended Seminars covering both NZS 54210:1989 Masonry Construction - materials and Workmanship and the Code of Practice for Non-Specific Design of Concrete Masonry NZS 4229:1986. Builders and Blocklayers should therefore acquire and familiarise themselves with both these documents which are available from SANZ, Private Bag, Wellington.
The above Standards cover only the most common masonry (clay bricks or concrete masonry units) used with Portland cement mortar, but it does recognise that other forms may be used.
It is hoped that NZS 4210 will promote a better quality of construction and lead to an increased level of confidence by designers in the quality and consistency of masonry so that its use is not penalised by increased safety factors to cover uncertainties.
Following are comments on specific items, or those Clauses from NZS 4210, which it is considered are important and with which the Building Inspectors wille expect compliance.
Starter Bars
Starter Bars must be set out to suit the cores of masonry modules, openings in walls, ends and corners. Maximum deviation is + 6mm. Bending of incorrectly located starter bars will not be accepted. Blocklayers must refuse to lay blocks, where the starter bars are incorrectly placed, until the problem has been rectified.
Reinforcing
2.6.2.1 “Vertical bars shall be fixed securely to starter bars unless required otherwise by specific design”.
2.6.2.2 & 2.6.3.2 Requires vertical and horizontal steel to be tied at crossings and vertical steel to be held in position at the top of the wall during grouting.
Laps
Laps for both horizontal and vertical steel shall be at least 40 diameter and must be staggered where two or more bars are in one cell.
2.7.3.1 Masonry units in partially filled blockwork are to be fully bedded on mortar to prevent leaching of cement or fines into adjacent hollow cores.
It is recommended that open-end blocks to use for all - cells - filled masonry.
2.8.3 Clean Out Openings
Clean-out openings are required at the bottom of all cores containing vertical bars, regardless of the height of the wall. Some variation from this requirement may be acceptable, but in no case will this requirement be waived where walls are over 1.2m in height.
2.1 Grouting of Cells
2.11.1 Grouting shall not commence until the mortar joints have attained sufficient strength to resist blow-outs and grout spaces have been cleaned out.
2.12.1 - 2.12.2.3 Grouting up to 3.6m is permitted provided an expansive admixture is used in conjunction with consolidation by rodding or vibration.
2.12.1 - 2.13.2.2 Where an expansive admixture is not used, grouting up to 3.6m maximum is permitted but grout must be placed in maximum layers of 1.2m and in conjunction with vibration.
2.17.1 Temporary bracing shall be provided to masonry where necessary to resist lateral loads during construction.
190mm walls up to 1m high become unstable in winds about 25 m/s and only 17 m/s at 2.4m high.
2.18 - 2.19 Blocks cannot be laid in icy or wet conditions. Some dampening of blocks may be permitted in hot windy conditions.
Plans
Builders are reminded of their obligation to keep the approved plans on site during construction so that they are readily available when requested by the Inspector.
Summary
Council's Building Inspectors will be checking that:
- Vertical and horizontal steel is correctly placed;
- Clean-out holes are available;
- All excess mortar is cleaned off steel and out of cavities.
In the event of non-compliance, further work could be halted.
We hope that builders will find this information of benefit in their day to day work and we ask for your continued cooperation in maintaining a high standard of building practice.
Should you have any further enquiries please clcik here to contact a Building Inspector.
Click here for contact details
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