Keeping Chickens On a concreate

Hi all My name is Rob, my wife and I are new to this site so if we offend anyone we are sorry!
 

We are new to keeping chickens we have two 22 weeks old orpingtons and are keeping them on a shed base, They are allowed to free range for about 2 hours in am and 2 in eve this will change and be longer in summer. I kept them on the grass in thier run to begin with however we dont really have alot of grass and they have over used this space. So i placed them on the slap is this OK?  Cleaning and scurbing the concrate seems easier and healthier.

We would be grateful for any suggestions. thanks 

I have 3 chooks on a concrete base (approx 2MX2M) it is covered with wood chips to about an inch thick.  They have been in there now for 3 months and have not had any issues.

I poo pick daily and then add at the week end give it a good rake through an top up of chips then a complete change and scrub monthly

They will be fine, cover the concrete with with a layer of miscanthus or wood chip and fill an old tyre with some sand or dry compost for them to dust bathe in. This should be easy to keep clean and the chickens will be happy scratching around in the run.

Liking the tyre idea as well, thanks for the tip