Plaster board finishing
March 19, 2019
There have been a number of instances where a client has had concerns with the level of finish provided to plasterboard lining. The plasterboard when viewed at certain times of the day or viewed with artificial lighting can highlight the location of joins, interior angles and fastener heads, which can appear to be unsightly or unfinished.
The information below will provide builders with the relevant guidelines required for the finishing of plasterboard required by Australian Standard AS/NZ 2589 – 2007 Gypsum linings – Application and Finishing and the Guide to Standard and Tolerances 2015.
The Guide to Standards and Tolerances specifies that the finish to plasterboard is defective when illuminated by non-critical lighting and has not been finished to a level 4 finish as described in AS/NZS 2589. This should be the minimal requirement specified in the building contact.
What is non-critical light?
Non-critical light means that the light that strikes the surface is diffused and is not glancing or parallel to that surface.
What is a level 4 finish?
All the joints and interior angles have the tape embedded in joining cement or jointing compound and a minimum of two separate coats of cement or jointing compound applied over all the joints, angles, fastener heads and accessories. The jointing compounds should be evenly finished, free of tool marks and ridges in preparation for decoration (painting).
For a minimum of a level 4 finish flat or low sheen paints should be used.
If the wall or ceiling is to be subject to critical lighting conditions (walls or ceilings are at parallel or perpendicular angles to window light) or a gloss, semi-gloss or deep tone paints are used, surface imperfections may still be apparent in the level 4 finish. In these situations it is advisable to apply a level 5 finish. Again this should be specified in the building contact as the work involved to achieve a level 5 finish would require additional cost.
The expected quality and areas of use for each finish level is listed below (extracted from AS/NZ 2589. 2007):
Suitable for appearance areas that are being finished with heavy or medium textured finish before final painting or where heavy grade wallcoverings are being applied. This level of finish is not generally acceptable for painted finishes or for light to medium weight wall coverings.
Suitable for areas where light textures and wall coverings are being used, where economy is of concern, or where a flat or low sheen paint finish is used in areas of non – critical light conditions. The finished stopping must be smooth and free of all tool marks.
Suitable for use where gloss, semi-gloss, low sheen or non-textured flat paints are being applied or where critical light conditions exist. To achieve a finish of level 5 on plasterboard and fibre – cement, a thin skim coat is applied to the entire surface of the sheets. For fibrous plaster linings, the final compound application is trowel polished.
For further information, please contact HIA Building Services on 1300 650 620.