Articles | Technical
Achieving a Level 4 or 5 Finish
Monday, 2 December 2019
By Graeme Robertson
Levels of finish is an age-old discussion where everyone seems to be an 'expert' but not everyone knows the facts. Watching a YouTube clip can magically turn a novice into an expert overnight and 'a friend told me...' gives confidence beyond ability to fully grasp what is actually involved.
So let me help bring some facts to the conversation.
Firstly, let's reference where all the facts come from. Winstone Wallboards is a product manufacturer, we make products to be used within and satisfy requirements based on the standards AS/NZS 2589:2017 Gypsum linings - Application and Finishing. Most of the recommendations and methods in our GIB® Site Guide and other literature are based directly on this and associated standards.
Let's start with Level 4
The key requirements of achieving a Level 4 finish are:
- 1 x base coat of GIB® jointing compound with GIB RocTape® or GIB® Paper Tape in the joint.
- A second coat of GIB® compound typically 170mm wide.
- A final coat of GIB® compound no less than 250mm wide for a tapered joint or 500mm for a butt joint.
- A joint build depth of no more than 2mm over the width of the joint and not forming a 'peak' (that means an obvious line).
Typically, Level 5 is specified where Semi-gloss paint is to be used and/or where Critical Lighting conditions occur. Including the requirements of Level 4 (as previously) Level 5 additionally requires:
- Tighter tolerances in framing preparation (AS/NZS 2589).
- All joints must be back blocked, walls and ceilings.
- An air-drying compound to be applied over the entire surface, this could be sprayed, rolled or troweled on.
When assessing the finished quality, this should be done at handover from stopper to painter. A coat of sealer can help highlight any imperfections while still showing the joint widths.
Standing 2 metres away from the wall under normal lighting conditions, not with a high powered light glancing across the surface, is the accepted way to inspect the finish.
Exposing the wall to any expected critical light may reveal an unexpectedly imperfect surface, even with a good level 5 finish.
Level 5 includes a skim coat however this is not to flatten the surface but to remove the differential porosity between the joints and the board face paper. If unwanted imperfections are still visible or highlighted with a level 5 finish under critical light, then either the critical lighting needs to be avoided, or a different finish applied to the wall for example, solid polished plaster.
Additional things to look for are:
- Over sanding whereas to damage the surface paper.
- No visible gouges, 'pin holes' or pock marks.
- Definitive tool marks.