Posted: 28/08/2016 at 19:20
North north east isn't the ideal aspect for grass, but it doesn't mean you can't have it.
I'd break the ground up well after removing some of your hardcore, then add a mix of topsoil, compost and grit. That will give you a good combination which will help with the clay problem, and also the (probably) undernourished ground. Grass doesn't need a huge depth of soil to thrive, so I wouldn't worry too much about the depth.
I'd wait till spring - mainly because the ground will settle over winter, so it means you can go over it and get it nice and level, and add more soil if you need to get it to a certain level. A general feed a week or two before laying the turf will also help provide some nutrients after the winter rain. Wait till the ground temperature and the general temperature is rising but there's still the likelihood of rain to help with getting the turf settled in. The climate where you are will determine the best time.
That's what I'd do anyway