Following on from the recent tip about creating a shade to give yourself more time when laying concrete, I’ve had a few calls asking why I didn’t mention polythene?!

The reason? Because there’s a number of things that can be done to give yourself a little more time, and we thought we’d send out one at a time to try to keep these tips short and snappy.

But yes, those of you who do use polythene will know it gives you a bit more time because it prevents the water from soaking into the dry sub base. Some people will wet the area down with a hosepipe, but to be honest, that never totally saturates the sub base and consequently will never be as efficient as putting down a layer of polythene. Also, wetting the base down will inevitably produce a base that is uneven in terms of wetness and dryness and consequently will produce a variable base onto which the concrete is laid, which will in turn affect the concrete surface too.

Other benefits of laying on polythene are reducing the chance of cracking in the short term (by reducing water loss and/or uneven water loss) and in the long term as the polythene acts as a ‘slip membrane’. Since, water is unable to soak into the sub base, there is more water available to keep the surface moist and reduce the chance of opening fissures resulting from the printing process.

Dr Concrete