So, I'm about to lift some turf and lay some new turf as well as extending the area. However, I'm very much a garden novice and have a couple of questions I'd like to ask you lovely people.

1. Do I have to add top soil to the area before laying the new turf? Or can I just add sand to the existing soil? (I have it on good authority that the garden soil is very fertile)

2. Do I have to do the ground preperation immediately before laying the new turf or can I do it the day before?

3. The area I'm using to extend the lawn has existing weeds. After removing the weeds should I use weedkiller on the soil or will this effect the new turf.

4. Away from the new lawn now - I'm also putting up some raised decking. I've cleared an area which was heavy with weeds. Should I put some weedkiller on the soil before laying a membrane or will the membrane be enough to keep the weeds at bay?

I would be very greatfull if someone would be kind enough to provide me with some advice on these issues.