Where the dwelling has been inundated with flood waters, it will be most likely that affected plasterboard will need to be removed.

In many cases it will be obvious where plasterboard has been soaked or contaminated but if in doubt, seek the advice of a professional tradesman to assess necessary actions. Over-eager early action, may remove more plasterboard than is necessary, so review the following information before stripping out the linings. If rectification work is to be claimed through insurance, make sure that you contact the insurance assessor to determine appropriate rectification actions.

Considerations:

• Identify the type of lining – Plasterboard, Fibre Cement Sheet*, Timber, Fibrous Plaster. Plasterboard may need removal from the level of inundation. Timber and Fibrous Plaster may not require removal and may simply require bleaching and washing down.
• Identify the safety hazards, sharp materials, nails, electrical, etc and use appropriate Health and Safety procedures.
• Where the board has attracted mould and has not been inundated, then a propriety cleaner with bleach or similar may be. This is usually all that is required to keep the mould at bay; however, oil of cloves can provide a longer residual mould inhibition giving a more lasting result.
• Plasterboard that has to be removed should be taken to the nearest board joint above the inundation level. Depending on the size of the plasterboard, this will either be 1200mm, 1350mm or full height, to the ceiling.
• Remove wet insulation.
• Surface and backing paper delamination is likely to occur down the track if wet plasterboard has not been replaced.
• Stud adhesive may also have been compromised and will not become evident until later.
• Contamination of sheeting by sewage, toxins and chemicals needs to be evaluated.
• Almost all ceilings that have been inundated will need to be replaced (especially where absorbent insulation is involved). Water will likely have ponded for too long a period, and all the fixings compromised as well.

*Please note, the document primarily refers to Plasterboard. Fibre Cement Sheet is different to Plasterboard and subject to different considerations and might not require removal. Fibre Cement Sheet should be carefully assessed as to whether or not it contains any asbestos – seek specialist advice on removal if sheets contain asbestos. Please contact the fibre cement manufacturer for guidance.

Removing Affected Plasterboard

There are two ways of doing this:

Method One:

Remove the damaged sheets to approximately 300mm above the high water mark preferably at the nearest joint above the water line. Given sheets are either 1200 mm or 1350 mm high it will either be at these joints or at full wall height (see 2 below).

Because the replacement joint will most likely be made up of one new recessed edge board abutting the existing sheet (a butt edge), the joint should be treated as a butt joint. There will be a crown created which may cause glancing light issues and setting out over 600mm (the same as a butt joint) will reduce the noticeability of the crown. See the Australian Standard AS/NZS 2589:2017 (Figure 4.4.5) for more information on setting out for butt joints. Note: A decorative dado rail may also be used over the new join without the requirement of troweling.

Method Two:

Fully remove the sheets to full wall height which will also involve the removal of the cornice.

This approach will usually necessitate the repainting of the ceiling unless a larger cornice can be applied over the area where the previous cornice was and there is no other damage evident.

Before Relining:

• Make sure a qualified electrician is satisfied with wiring prior to sheeting.
• The framing must be dry (less than 16% moisture content) and the screws removed.
• Stud adhesive can be removed using a sharp chisel or more effectively, an electric planer, bearing in mind not to plane the studs.
• Clean out any debris above the bottom plate
• Do not reuse water damaged insulation.

 Downlaod Document PLASTERBOARD RECTIFICATION RESULTING FROM FLOOD INUNDATION