SPR Rendering has been rendering across Sydney for over fifteen years. Houses, fences, retaining walls, commercial buildings and everything in between. We quote on site, we tell you what the wall actually needs, and we finish what we start.
What cement rendering actually is
A cement render is a wet mix of washed sand, cement and usually lime, trowelled onto a masonry wall in layers. The first coat, the scratch coat, keys into the wall and is scored to give the next coat something to grip. The second coat is floated flat and then finished, either smooth with a sponge or steel float, or left open for a texture coat to go over the top.
The lime is the part people leave out and it matters. Lime makes the mix workable, lets the wall breathe, and gives the render a small amount of self healing ability where hairline cracks form. A straight sand and cement mix with no lime is harder, more brittle, and far more likely to crack and debond.
Total thickness on a typical Sydney brick wall ends up between 10mm and 15mm across the two coats. Thicker than that in one hit and it will sag and crack while it cures.
Which walls suit cement render
Cement render bonds mechanically, which means it needs something to grip. Anything porous and textured works well.
- Clay brick, both common brick and face brick that has been keyed
- Besser block and concrete block, which is close to the ideal substrate
- Poured and precast concrete, with a bonding agent first
- Rendered walls being recoated, once the old render is sound and clean
- Sandstone and older sandstock brick, with a softer heritage appropriate mix
Which walls do not suit cement render
This is the part most quotes skip, and it is the reason most render fails. Cement render will not hold on a surface it cannot key into.
Painted brick is the big one. If a wall has been painted, the render is bonding to the paint film, not the brick, and the paint film is bonding to a wall that has been sealed for twenty years. It will let go. The wall either needs the paint mechanically removed or it needs a purpose made bonding system. Both are more expensive than bare brick and both are far cheaper than doing the job twice.
Blueboard, Hebel and other lightweight panels also need their own systems rather than standard cement render. We cover those on the blueboard rendering and Hebel rendering pages.
How long a cement render job takes
For a standard single storey Sydney house with around 150 square metres of wall area, allow about a week. Two days to set up, sheet everything down and get the scratch coat on, a day for it to go off, two days for the top coat and finishing, then a day to clean up and pull the scaffold.
A two storey house is closer to two weeks because of the scaffold and the extra area. A front fence is two to three days. A single bathroom is one day.
Curing is the part you cannot rush. Cement render gains its strength slowly and it needs to stay damp while it does. In a Sydney summer we will mist the wall down for the first few days rather than let it dry out too fast and craze.
Cement render or acrylic render
Cement render is harder, cheaper per square metre, and breathes better. It suits solid masonry, it takes any finish you want to put over it, and it is the traditional choice for good reason.
Acrylic render is polymer modified, which makes it flexible. It goes over substrates cement render cannot handle, it copes with movement and thermal cycling far better, and it is the right call on coastal walls, on lightweight panel, and on anything that moves. It costs more.
Most Sydney jobs end up as a cement render base with an acrylic texture coat over the top, which gets you the strength of one and the flexibility and colour range of the other. We will tell you which way to go when we look at the wall.