17 Jan Four essential laws of gib stopping
Gib Fixer Rules
These rules of gib fixing are fundamental to creating a longer-lasting, better looking finish. Understanding these simple rules will help you find a quality gib fixer, because you’ll be better able to ask questions about their processes before you hire them and more likely to spot any incorrect practices.
Gib fixer rule 1: Fix gib to avoid light falling across joins
Gib plasterboard needs to be fixed in way that prevents light running directly across gib plasterboard joins.
This is generally done by fixing sheets so that the joins to run in the same direction as the main light source. In most cases this means the gib is fixed horizontally on walls. However, light can sometimes run vertically, such as with skylights or in smaller, darker rooms.
Gib fixer rule 2: Minimise the use of butt or cut joins
Butt joins are formed when two non-tapering ends meet. To minimise butt joins we order gib specifically to fit each wall and ceiling and use the longest practical sheet size.
Instructions for sheet layout are written on framing members, and these are followed by our gib fixers. If in doubt, our gib fixer will apply these rules to select the sheet layout.
Where butt joins can’t be avoided, we minimise them by placing them above doors or windows, provided they comply with gib fixer rules 3 and 4.
Butt joins in ceilings should be staggered to make them less visible.
Gib fixer rule 3: Keep joins away from areas prone to movement
Areas with a lot of movement are more prone to defects, so gib fixers need to avoid placing joins in these places.
Areas prone to movement include:
a) Near the corners of doors and windows. We keep joins at least 200mm away from these corners to avoid cracking.
b) Junctions between rooms or hallways.
c) Stairwells or mezzanine floors. This is the most common place for plasterboard defects to develop. Defects are easily visible because of the long lengths of timber in these areas (so any timber shrinkage has an effect over a long distance). Another place to watch is junctions between two floors, where lateral forces come into play as the building settles or moves. Our gib fixers avoid creating joins near the junction of two floors.
Gib fixer rule 4: Back-blocking for ceiling joins and stairwells
Back-blocking strengthens and stabilises joins between plasterboard sheets. New Zealand standards for gib plasterboard state that where three or more joins occur on a ceiling, they should be back-blocked. PBF gib fixers actually backblock all ceilings and stairway walls with more than two joins running horizontally. This minimises the chances of peaking as timber expands or contracts.
While some builders and gib fixers do employ the practice of back-blocking, most use contact adhesive or standard setting compounds. PBF gib fixers install back-blocks using a highly adhesive plaster-based compound called cove bond. This method is relatively rare, despite being the only correct method recommended by gib and other plasterboard manufactures. The strength and rigidity of the cove bond keeps pressure off the join to prevent cracking. This information is based on the AS/NZS 2589: 2007 guidelines for plasterboard (gib board) installation.
Design and construction issues
At PBF we often come across design or building issues which directly compromise the reliability and visual appearance of the finish. No matter how well our gib fixer does their job, these things can lead to higher chances of cracking, peaking and popping.
That’s why we recommend you consult your gib fixing expert early in the building process to avoid these issues.
For example, your gib fixing specialist may point out:
- Use of timber ceiling battens (these are very prone to movement)
- Framing that does not comply with NZS 3609: 1999
- Framing that is too high in moisture content
- Ceiling batten layout
- Omission of control joins
If you would like more information or a quote for your gib fixing project, please contact us.