CB Concrete, blocks & bricks

Solid masonry and veneer

Most brick homes are brick veneer. Brick veneer is built with a cavity between the timber framing and the brickwork and is built with drainage cavities at the base of the wall. The main maintenance required for brick or masonry veneer is to ensure the drainage cavities at the base are kept clear. Paint applied to the brick or block will be purely cosmetic and will not improve the weathertightness.

Note: Never fill the cavity behind the brick veneer with an insulation product as this will seriously alter the weatherproofing performance of the cladding.

Most solid concrete block homes are constructed from reinforced masonry. This means the concrete blocks have reinforcing inserted into them and then they are then filled with concrete. Because the concrete blocks form the full thickness of the wall and are often exposed on the inside or are covered with a lining the reinforced masonry relies on the externally applied waterproof coating for weathertightness and this must be maintained to keep water out.

Cracked/crumbling concrete

This could be due to corrosion of the reinforcing, shrinkage, tree roots, building settlement, incorrect installation or corrosion of an embedded fitting.

For stationary hairline cracks, recoat the wall with an acrylic coating designed to bridge hairline cracks.

For cracks wider than hairline, structural fixings or the crack is still moving seek professional help. You can monitor the crack by putting a piece of tape across the crack, if it tears the crack is still moving.

Cracked bricks/blocks

This can be due to building settlement or a lack of control joints. Seek professional advice. This could also be due to earthquake. Contact the Earthquake Commission if you need to make a claim for damage as a result of an earthquake.

Crumbling bricks

This can be caused by moisture penetration, frost or a manufacturing defect.

If the bricks or blocks are structural, seek professional advice.

If the damage is cosmetic, address the cause of moisture if possible. Check for soil buildup or overhanging trees.

Cracked/crumbling mortar

This can be due to weathering or damage from creepers. It can also be due to settlement, tree roots or insufficient control joints which allow for movement in the wall.

Monitor the crack width for six months. You can do this by putting a piece of tape across the crack, if it tears the crack is still moving. If the crack is stable, replace the damaged bricks and mortar (you’ll need a bricklayer to insert the control joints). If the crack is still moving, contact a professional.

Wash down at least once a year to extend the life.

Cracked lintels

This can be due to settlement or corrosion of the lintel bar.

Monitor the crack width for 6 months. You can do this by putting a piece of tape across the crack and if it tears the crack is still moving.

If the crack is still moving seek professional advice. If the crack is stable, replace damaged bricks and mortar. If corrosion is newly visible, remove the corrosion and prime with zinc rich primer, metal primer and repaint. Where corrosion is extensive, contact a professional for advice.

‘Drummy’ sound from plaster

This is due to the plaster losing its bond with the concrete or substrate.

If it is just a small area, you can leave it and monitor the damage. For larger areas, seek professional advice.

Blocked drainage outlets

At the bottom of all cavity-based cladding systems are ventilation holes or slots. These should be checked regularly to ensure soil, bugs and plants are not blocking them. This prevents water draining properly from the cavity and reduces airflow in the gap between the brick and the framing. This could allow moisture to penetrate the framing.

Keep plants and soil clear of the base of the wall. Lower the garden level if necessary. Do not allow driveways or paths to be cast against brick veneer. Ensure the landscaping directs water away from your home.

Ventilation slots blocked/absent

If the ventilation slots at the top of the brick veneer are blocked, or if there are no ventilation slots, this will prevent proper ventilation and drying.

Clear out any blockages. If you need to insert ventilation slots, scrape out the mortar on every third vertical joint or replace bricks with venting units at regular intervals.

Patchy colouring

This can be caused by uneven runoff or the area not being rain-washed.

Divert the runoff if you are able to. Wash the wall more often.

Deteriorating paint

This can be due to normal weathering or moisture getting in behind the paint.

Address the cause of the moisture.

Correctly applied masonry paint should last for about 12-15 years before it needs replacing if the masonry was properly prepared. If the paint has come to the end of its life or has deteriorated early, wash down the wall, remove loose paint and repaint with acrylic paint. Ask your painting retailer for advice on the best products to use.

Efflorescence or white deposits

This is caused by moisture.

Dry brush off the deposits before washing down the affected area with detergent and clean water. This will clear away the deposits but may not prevent its recurrence. Address the cause of the moisture. See www.branz.co.nz Bulletin 442 “Efflorescence on Masonry” for more information. Note you will need to pay for this information.