Remedies: wall claddings

Claddings may still be in good condition, but some claddings may need repair or replacement.

Brick veneer cladding

Historically, older brick veneer houses have not performed well in major earthquakes. This is because the wire ties fixing the veneer to the timber frame failed through corrosion or pull out, or there were not enough ties installed.

Without removing and replacing the brick veneer cladding, it is impossible to assess the extent of the corrosion or replace the wall ties. Many people also do not understand that brick veneer, like other claddings, requires maintenance (Figure 1).

Check brick veneer for evidence of cracking or damage. If there is cracking, the cause, and whether or not it is widening, must be determined. Cracks may occur because of:

  • settlement - determine if settlement is still occurring by monitoring the width of the crack. If it remains static, a decision whether to accept the movement that has occurred and work around it must be made. If it is increasing in size, the building may need to be underpinned and made stable following a specific engineering design. In severe cases it may be necessary to remove the veneer and either repair the problem and reinstall it or where the load on the foundation needs to be reduced install a lightweight cladding system.
  • earthquake damage - if this is the cause, damage may not get worse so cracks in joints can be repointed and cracked bricks may be able to be replaced. If cracks are widening, specialist engineering advice and design is required.

Other problems that may need to be addressed with brick veneer are:

  • deterioration of the joint mortar - joints may need to be raked out and repointed.
  • corrosion of lintel bars - remove the rust and treat with a specialised coating system. For severe damage the steel will need to be replaced which will require removal of some of the veneer.
  • blocked veneer drainage/ventilation which will require cleaning out.
  • veneer cavities that are open to both the roof and subfloor spaces which allow moist air into the roof space where it can condense of the underside of metal roofing and result in damage to roof underlay, insulation and ceiling linings. Options to remediate the situation include closing of the cavity if possible, raking out some joints in the bottom course to provide drainage and ventilation and covering the ground under the house with polythene.

If renovation work is being carried out it is essential that mortar droppings or rubbish do not fall into the cavity between the brick and the timber framing as it will restrict ventilation and may hold moisture, both of which will facilitate the movement of moisture across the cavity.

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Timber wall cladding

Horizontal timber weatherboards that have been well maintained are likely to still be in sound condition (Figure 2). Any deterioration is likely to occur at running joints in boards and at mitred corners which were more susceptible to water entry.

Rusticated board may have also cupped, which opens up the lapped joint increasing the risk of water entry (but also allows air in to dry some of that water). Cedar, which has very defined seasonal growth patterns in the grain, may have significant erosion of the softer wood, particularly when unfinished and in coastal locations where there is wind-blown sand.

Vertical shiplap and board and batten cladding, while likely to still be sound, may have cupped, which can allow water in.

Other problems that may need to be addressed with timber cladding are the replacement of:

  • corrosion of metal flashings and fixings
  • rotted timber at the bottom of the wall particularly where the outside ground level is close to or against the cladding
  • cover battens that have split or cupped 
  • plywood that has surface checking or splitting.

See matching new to existing for information about matching new weatherboards need to existing ones.

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Asbestos-cement wall cladding

Asbestos-cement materials will typically last about 50 to 60 years, so asbestos-cement wall cladding may still be sound, particularly where it has been regularly painted and protected from wind-blown sand which can erode the surface.

Replacement may be needed where uncoated material has a weathered surface or the sheets/planks are cracked or damaged, particularly for sheets at the lapped joint and corners. See Asbestos for handling and removing asbestos safely. Removing asbestos-cement wall cladding must be carried out by a licensed asbestos removalist. You can find a registry of licensed removalists on the WorkSafe New Zealand website.

Sheets were fixed with galvanised flat head nails and these may be corroding as the zinc coating has eroded or was damaged during fixing - minor corrosion should be removed by sanding, but where fixings have deteriorated badly, cladding may need to be replaced.

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Check stucco for evidence of hairline cracks or damage. If there is damage that does not warrant the replacement of the stucco, repairs can be made by carrying out the following:

  • Chip out and remove loose plaster around the damaged areas.
  • Add new mesh at corners where necessary.
  • Refinish the area by 'bagging', that is, wet the area needing to be refinished, and then smear new plaster over the crack, working it into the gap and spreading a thin layer over the adjacent surface.
  • Repaint the whole exterior once repairs have been completed. Very fine cracks may be adequately repaired by painting with a flexible acrylic paint.

Work on a plaster-based cladding system that goes beyond the minor repairs and maintenance covered by Schedule 1 of the Building Act is restricted building work (RBW). All RBW requires building consent. Anyone carrying this out must hold an external plastering licence or be supervised by someone who does.

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Hardboard weatherboards

The original hardboard weatherboards still remain on some buildings. Those later installations that failed have generally been replaced by the manufacturer (usually with a fibre-cement plank). When coatings have been well maintained, by a regular repainting regime, original weatherboards may still be in relatively sound condition. If boards are in poor condition, replacement will be required.