Unfortunately, accidents happen. Never by design but they happen. If there has been an ‘event’ which involves water where it shouldn’t be — where to from here?
Firstly, we need to get rid of the immediate problem, preferably as fast as possible. Let’s get this water out of the picture and see how bad it is.
What to consider when assessing the damage:
- Was the water clean or ‘dirty’? Dirty means anything other than clean water from internal pipes, eg. sewage, flooding from a creek or surface overflow from a neighbouring site. Dirty water carries all sorts of nasties, so the plasterboard will need to be replaced.
- Is there any mould? Presence of visible mould means there’s a high chance of trouble going on behind, where you can’t see.
- Are there multiple layers of plasterboard? It is very difficult to adequately dry between layers of plasterboard, so this generally would be considered for replacement.
- How long has it been since the ‘event’? If it’s been less than 48 hours and you are getting things on the way to dry, then you have greatly increased your chances of salvation. Anything past 60 hours and the ship has sailed.
- Is the insulation wet? Unfortunately, wet insulation is nigh on impossible to dry out as it tends to get waterlogged. This holds the water behind the board and is the perfect breeding ground for mould.
As plasterboard is generally an interior use product, the assumption is that the building is and will remain E2 compliant and stay dry. If there is continual water contacting the board, even if it fully dries out each time, the gypsum core will eventually weaken in its structure and become crumbly within the paper face/back.
OK, so if it’s getting dry and it passes the criteria above you are probably going to have a high chance of saving the board.
If it doesn’t, you need to consider replacing the board.
Replacing Water Damaged Board
The level of difficulty replacing the water damaged board will be determined by accessibility, how many layers and if it’s a 'performance' system. Keeping in mind a 'performance' system is dependent on the individual components remaining dry in service to remain effective for the life of the building — typically 50 years according to the building code.
If it is a bracing element, the minimum size part sheet in a brace wall is 300mm so at a minimum, you will need to replace the bottom 300mm. Where sheet butt joins occur, it is best practice to back-block with GIB Cove Bond. All joints must be taped and stopped as per GIB Site Guide.
If it is a firewall, all sheet edges/joints usually must be fixed on a solid member as a minimum* (stud or nogg). If there are two or more layers on one side, these layers must be overlapped by a minimum of 200mm and the sheet edge of each layer must have its own solid fixing.* Again, all joints on the outer layer must be taped and stopped as per the GIB Site Guide.
If there is any mould on the face of the board, this can sometimes be dealt with by killing the bacteria by using a suitable chemical, but care must be taken to not damage the paper back/face. Please be aware that mould spores can sometimes be deeply ingrained in the core and 'survive' cleaning, so this is definitely not the preference.
In addition, to achieve the optimal quality of the overall finish, the stopping compound, paper face and gypsum core need to be 'as new,' the timber framing needs to be fully dry to avoid future screw popping, which can sometimes happen even six months after the wall was lined. This is generally due to timber shrinkage.
Adjacent surfaces need to be free of paint/wallpaper. The sheet joint and any large voids, can then be filled and taped with GIB Tradeset 20 or 45. Once dry, topcoat with an air drying compound like GIB Plus 4, which can then be followed by a good sealer and paint.
* Check the relevant System Literature for details.
For further information visit gib.co.nz or call the GIB Helpline on 0800 100 442.