laying new lawn

oh come on, don't be so lazy

Firstly the very reason you're laying the lawn is that you want your lawn to be weed free and have a smooth, relatively flat surface.

If you lay turf directly over an exsisting lawn the weeds and grass that are part of your exsisting lawn will come up through it due to the fact that they still have roots down there.

Whatever problems you have or for whatever reasons you have for wanting a new lawn, the problems and reasons will persist if you lay over an exsisting lawn.

You might go ahead and do it (lay the turf over the exsisting lawn) and for a short time you will get the desired results, however more time will show you that you will be straight back where you started from.

Ok good luck

If you all ready have an EXCITING lawn why lay another!!!Sorry I couldn't help it!! If I were you I would kill off the old lawn wait a few weeks for it to die and then level out anything that needs it and lay your new turf.
You will then get rid of SCDCREATIONS EXSISTING lawn !!!!!!sic

You don't mention what the problem is the the existing lawn - if there are bare patches, you could just re-seed those - possibly with a more hard-wearing seed mix?