Render Curing Before Painting

[bryntwr]

Hi All,

I've had fresh render (cement, sand), how long do I need to wait before painting as a minimum. I keep getting conflicting information.

I am going to be using xtreme xposure sandtex.

Kind Regards

 

[cjard]

You're probably best off waiting until it's dry. As to how long that is depends on the environment but 1 day per mm thickness plus 7 days is probably average

 

[bryntwr]

Hi,

It's been very hot here (20 degrees plus for around two weeks). It's 15mm, so would you say 22 days would usually suffice?

Is there any way to check that it is dry?

Thanks

 

[cjard]

Heat doesn't necessarily help: clothes on a line dry faster on a temperate windy day than a hot still one, so airflow is a major factor.

You can ask the paint manufacturer what the maximum moisture content of the substrate may be and then measure the render (break a bit off or obtain a bit of waste, weigh it, bake it in a hot oven for a few hours then weigh it again). Other moisture gauges that are less 'destructive' exist, but you could just do what most ordinary people would do- ignore the science bit, leave it a while, then a bit longer, then paint the oldest bits first and hope for the best. End of the day, no one on a forum without seeing the job, will be able to say for certain that it's all good. Call in a painter if in doubt

 

[bryntwr]

Hi cjard,

I won't be able to break off a section as it is newly rendered with no waste on site. Any other solution?

Thanks