Exterior walls general maintenance

Keep a file of the materials you use when building or maintaining your home. This will help you to make good decisions about maintenance. It will also help future owners of the house. It’s particularly important where materials have guarantees of 10 or 15 years or more. Information on the materials used should also be on the building consent permit issued when the house was built.

Cracked/flaking paint

This is the first sign that the paint is failing. It can also be a sign of rot or moisture. It could be due to incorrect preparation when the paint was first applied. Paint manufacturers have very detailed information on their products to help you choose, prepare and apply the correct product.

Sand or scrape off existing paint, and prime bare cladding before repainting. For concrete, repaint with a suitable paint (such as acrylic or cementitious). If in doubt, check with the manufacturer of your particular cladding.

If moisture is the problem, address the cause of the moisture. Replace any rotten timbers or cladding.

Dirt/salt buildup on cladding

This can shorten the life of the cladding material.

Wash down the walls, windows and frames regularly. This is particularly important for houses near the sea or in geothermal areas (and check for cracks or damage to the cladding at the same time).

Concentrate on areas that do not get rain washed, such as under eaves and at the top of the garage door. Use a soft brush and low-pressure hose. Do not use a high-

For sea spray, moss and lichen, you might have to use specific cleaning products – check with the manufacturer of your cladding and your local hardware store about the suitability of the product for your cladding.

Some cladding systems specify how frequently they need to be washed to validate the warranty.

Paint chalking

This is due to natural weathering.

All paint chalks. Minor chalking will not affect performance but chalking eventually causes the coating to thin. You will need to remove the chalking to prepare the surface for repainting.

The base of timber and metal cladding can rot or be damaged if it comes into contact with the ground or with paving.

If left, moisture will get into the cladding and framing, leading to more serious damage. Address the cause of the damp. Remove soil and plants from around the base of the walls. You may need to install intercept drains to capture surface run-off. Ensure that paths, driveways or landscaping do not direct water towards or under the house.

Dry out and repaint according to the type of cladding.

Mould, lichen and moss growth

This can be due to damp environmental conditions, a leak, overflowing gutters or trapped water.

Address the cause of the dampness if you can. Identify and repair leaks and clear the gutters out. When cleaning out gutters, disconnect the downpipe or put a tennis ball or chicken wire over the top of the pipe to prevent blockages in the downpipe.

Clean the mould with a 1:4 bleach solution and soft brush. Hose off residue with plenty of water and avoid using ladders around wet areas as much as possible. Bleach can damage plants, so you may want to protect surrounding vegetation with plastic sheeting.

Moss and black slime can build up, especially over winter. Water blast or scrub with a solution of household bleach and water. See the bottle for dilution instructions. Let the solution dry, then hose off.

Remember to remove the tennis ball afterwards!

Holes in the cladding

Holes will let water in, as well as mice, rats, slaters, birds or bees. Slaters eat damp wool insulation!

Block up the holes and, for mice or rats, lay poison bait blocks. If set early in winter, mice get wiped out before they start nesting – leaving your house mouse-free for the winter.

Do not block drainage gaps in the cladding system.

Corroded nails/fixings

This can be due to moisture and salt corroding the fixings. It can also be caused by copper from treated timber or acidic cedar.

For rusted nails in painted timber, remove the corrosion by sanding before punching the nails in, filling in the hole with putty, and repainting.

For other claddings, sand off the corrosion and prime with zinc rich primer, metal primer and two finish coats.

Stainless steel is more expensive but will last longer in marine environments. Use stainless steel wherever the fixing is used with treated but unpainted timber and there is moisture present.

Corroded flashing

This can be due to damp environmental conditions, run-off from copper-based preservative treatments or a lack of rain washing.

This could also be due to the flashing material not being compatible with the cladding leading to bi-metallic corrosion.

Replace badly corroded items. For other galvanised items, sand and prime with a zinc rich primer. Apply a galvanised iron primer and two topcoats.

Address the cause of the dampness if possible. Regularly wash down the walls.

Water dripping from overflows

This can damage the cladding. It could also be wasting your money if it is from a hot water supply or if you pay for your water.

Remove any surface mould and check that the water hasn’t got into the cladding. See leaking overflows for more information.

Stained wall surface

This could be due to a number of different causes and the treatment will vary accordingly.

Sealant degrading at joints

This is due to the effects of sunlight. You can remove the existing sealant and replace with exterior grade paintable sealant. However, this is a complex task as you need to take care not to damage the back of flashings or building wraps. These all need to be intact to maintain the integrity of the cladding. Follow manufacturer’s instructions for this.