How long new render needs before it is painted

Waiting feels like lost time, but coating render too early is one of the easiest ways to shorten its life. This guide sets out the waiting times the makers publish, so you can plan the job and the painter around them. For coatings over render, see our texture coatings page.

Why does new cement render have to wait before it is painted?

Cement render cures by a chemical reaction, not just by drying. While it cures, the surface stays strongly alkaline and still holds moisture. Coatings put on too early can fail to bond, blister or discolour. That is why coating makers set a minimum time on new cement surfaces: 28 days for Dulux AcraTex Sedona, and 30 days on another AcraTex data sheet. Pre-blended renders can be quicker: Rockcote's Quick Render Fine can be painted after 48 hours, while it says site-mixed sand and cement still needs 28 days.

How long does each kind of render need?

The sources are the Rockcote Polymer Render data sheet, the Dulux AcraTex RenderWall Plus product page, the Mortatec Classic Render data sheet and Building and Energy WA's bulletin on white set plaster. Other makers set other times, so check the data sheet for your system.

Does the weather change the waiting time?

Yes, and it also limits when render and coatings can go on at all. Makers set temperature limits in their data sheets:

• Davco's cement render must not be applied above 30°C or in hot, windy weather, which dries it too fast to cure properly.
• Rockcote's polymer base coat must not go on when the air or the wall is below 5°C or above 35°C.
• Dulux's texture coating must not go on when the wall is above 40°C or below 10°C, or when relative humidity is above 85%.

Cold, damp weather slows curing and drying; hot, windy weather can dry the surface before it has cured. In a Sydney summer, rendering starts early and follows the shade. In winter, coatings wait for drier days.

What paint or coating goes on render?

Over cement render, the coating has to cope with the fine shrinkage cracks that appear as render ages. Dulux recommends against ordinary low-build paint over cement render because it cannot bridge those cracks; a texture or membrane coating made for render can. Our texture coatings page explains the systems.

Does acrylic render need painting?

Not straight away. In an acrylic system the colour is in the tinted finish coat and topcoat, so the wall is finished when the topcoat goes on. It is recoated later, when the maker's maintenance guide says, rather than painted as part of the job.

Can the render be painted sooner if it looks dry?

Looking dry isn't the test. A surface can be dry to touch while the render under it is still curing. If a job has to move faster, the better answer is a system designed for it, such as an acrylic system with short times between coats, chosen before the work starts, rather than coating cement render early.

How do we plan the coating on our jobs?

We tell you at the quote which coats are included and when each can go on, so you can book the painter, or plan the texture coating with us, for the right week. If a job runs into hot or wet weather, we move the work rather than cut the waiting time. To see what the coating adds to a budget, read what cement rendering costs in Sydney.