Rendering near you

The substrate decides the specification, not the look on the sample board. A dense, modern extruded brick, a soft old clay brick, a concrete block, an autoclaved aerated concrete panel and a fibre cement board all absorb water differently and move differently, and a render mixed for one will craze, delaminate or drum on another. The rule that matters is the same one that governs mortar: the coating should not be stronger and harder than what it is stuck to, because when the wall moves the stress has to go somewhere, and if the render wins, the masonry face loses.

Exposure matters as much as strength. The Code classifies masonry materials by exposure, with a class specifically for severe conditions including salt attack and salt spray, and a wall in a coastal suburb that is already fretting will push salts through a new render and blow it off in patches. Rendering over an active salt problem hides it for a season or two, which is why a careful renderer will want the cause dealt with, the affected units replaced and the wall allowed to dry before anything is applied.

On heritage and character housing, ask specifically about lime. Older solid walls were built to absorb water and dry outward through soft mortar and soft render; sealing them behind a hard modern cement coat traps that moisture, and the damage appears as blown render, salt crystals and decaying joinery. A lime-rich, vapour-open specification is usually the right answer, and it should be written on the quote rather than assumed.

Preparation is most of the job and most of what separates quotes. Expect the wall to be assessed and cleaned, loose and fretted units and sandy joints to be made good first, unsound existing coatings to be removed rather than covered, bond to be checked, and control joints in the substrate to be identified so they can be carried through the render instead of being bridged. Where a masonry wall has vertical articulation joints, which the Housing Provisions require at not more than 6 metre centres in straight walls at not less than 10 millimetres wide, the render must have a matching joint in the same place. Rendering straight across one guarantees a crack in a straight line within a year or two.

Then the setting out at the bottom and around the openings, which is where most render failures are designed in. The damp-proof course must be continuous through the wall and visible from the outside face of the wall, so the render has to stop clear of it, not run down past it into the ground. The Code's minimum heights for the damp-proof course above ground are 150 millimetres above adjacent ground level in the general case, 75 millimetres above a paved area that slopes away and 50 millimetres above a protected paved area, with lower figures only in low rainfall intensity areas. Weepholes, which must be at least 50 millimetres high at not more than 1.2 metre centres, have to stay open, and the render must be stopped and beaded around them rather than smeared over them.

Application and curing come last and are the least negotiable. Coats go on in the specified thickness and sequence, each allowed to set before the next, and the finished work is protected and cured. Ask what the plan is for weather: fresh render in hot, dry, windy conditions loses its water before it gains strength and crazes, and rain on a green surface leaves permanent marking. Ask too what happens if the wall opens up worse than it looked, since fretted brickwork and a bridged damp-proof course are the two most common variations on an Australian render job.

Bridging is the first and worst. Render taken down over the damp-proof course, or onto a path or paving poured against the wall, gives moisture a continuous path up from the ground into the wall above, and the result is rising damp with a tide mark, blown paint, salt crystals and damaged skirtings inside. It is entirely avoidable and it is the single most common defect in rendering older and retrofitted Australian houses. The same applies to render that closes the weepholes or fills the base of a cavity: the wall loses the drainage it was designed around.

Drumminess and delamination come next. Tap a rendered wall and a hollow note means the coat has lost its bond, usually because it was applied over dust, paint, a sealed or very dense surface, or a mix too strong for the substrate, or because salts are crystallising behind it. Patching a drummy area without finding the reason means the patch lets go as well. Cracking divides into fine crazing from a mix that dried too fast, and directional cracking that follows the movement of the wall, which is the sort that runs from the corner of an opening or in a straight vertical line where an articulation joint was bridged.

The last one is paint. A rendered wall still has to let water vapour out, so a heavy film-forming coating over a wall that is damp, salty or still drying will blister and peel and will keep doing so until the moisture is dealt with. On a coastal wall, salt deposits will reappear through the coating. The order of operations is always the same: find the moisture path, fix it, let the wall dry, then coat it with a system suited to render.

Rendering is a licensed trade in the two largest states, under names that do not contain the word render in New South Wales and do in Queensland. The QBCC issues plastering solid as a trade class, and its published scope includes applying solid render, applying trowelled texture-coat finishes, applying float and set coats for hard plaster flat surfaces, installing pre-cast decorative mouldings and constructing plaster mouldings, with a variant that excludes the painting component. New South Wales licenses the same work as wet plastering, defined as applying a mixture of lime, cement or gypsum plaster and sand and water, or other materials achieving a similar result, to cover internal or external walls and ceilings, and noting that it can be applied to brick, stone and concrete surfaces or to existing sheet and board linings. A contractor licence is required for residential building or trade work above the Home Building Act value threshold.

Elsewhere the pattern follows the general building system. Western Australia registers building practitioners and contractors through the Building Services Board, supported by Building and Energy, under the Building Services (Registration) Act 2011, with a higher value threshold for Class 10a work than for other building work. Victoria registers building practitioners and regulates domestic building contracts through Consumer Affairs Victoria, where domestic building insurance must be taken out by the builder above the contract threshold and the certificate of currency given to you before any deposit or other money is taken, responding to structural defects for six years and non-structural defects for two. Whether a building approval is needed at all is a local question: like-for-like rendering is usually maintenance, while changing the external appearance of a property in a heritage or character overlay frequently is not.

LokalMatch handles the first step only. You describe the rendering job once, including the wall type, whether it has been rendered or painted before, the approximate area, the number of storeys, the age of the house and anything you have noticed about damp or salt, and matched renderers and solid plasterers contact you directly. Those businesses pay for the requests they receive. LokalMatch does not render walls, does not set or quote prices and does not vet, rank or recommend any business, so checking the licence class, the insurance and the references is your part.

Seasons run the other way here, so the northern hemisphere rule of thumb about rendering in the summer is wrong twice over. Australian summer is December to February and it is often the worst time to render in the inland and the north, because heat, low humidity and a dry wind pull the water out of a fresh coat before it has developed strength, which shows up as crazing and a weak, dusty surface. Australian winter is June to August, and in Melbourne, Hobart, Canberra and the tablelands it brings cold nights and slow drying, and inland frosts that fresh render will not tolerate.

That leaves the shoulder seasons as the sweet spot in most of the country: autumn from March to May and spring from September to November. In the tropical north the more useful frame is the wet season and the dry, and render work is scheduled in the dry months when a wall can be prepared, coated and cured without a storm arriving in the middle of it. Wherever you are, ask how the renderer intends to protect the work from sun, wind and rain while it cures, and treat shade cloth, damp curing and staged coats as signs of a job being done properly rather than slowly.

There is a sequencing benefit to timing as well. Render is the finish that goes over everything else, so it should follow any brick repairs, any re-pointing, any work on flashings, gutters and downpipes, and any change to paving or garden beds at the base of the wall. Doing it in that order avoids the two expensive Australian mistakes: rendering over masonry that still has to be repaired, and rendering a wall whose damp-proof course is about to be buried by the landscaper who comes next.