are you sure that you want leylandii there are much prettier ideas for privacy hedging, click on H at the bottom of the page and go to hedging plants , theres lots of photo's-- sorry Love2 but personally I really do not like them, they grow like 'topsy' and do not support wildlife or allow underplanting there are other shrubs and conifers that are not such thugs :o( ( sorry )

Don't bother, they are more trouble than they are worth.

in africa
thats is proberbly close enough, sorry not my favourite.guick growers,large roots and very expensive when you want to remove them in 4 years time because nothing grows near them.

I so wish I had planted them two years ago. By now they would be half way to blocking out the view of the loft extensions several neighbours have built in that time!

Don't plant them, seek advice. I suggest something like privet or varigated holly, a little bit more expensive but will give much more pleasing results long term, and holly is good for security.

if you are set on large conifers try googling Thuja plicata this is sold for hedging, is similar to leylandii but is the 'good guy' against the Ley.s 'bad guy'
hope you find something

thanks to everyone who responded,i don't wish to appear rude but i asked a simple technical question and all i've got back is opinions.i wanted to plant them because i'm having trouble with local kids hitting the house with footballs and it's driving me mad.i just wanted something that grows quickly. i won't bother anymore,i will put a fence up instead.

Love2drive, i'd ask at the nursery/garden centre where you'll be buying them from - they should have knowledge on the planting distances.
I think the height of the plant you buy determines its planting distance, e.g. smaller the plant you buy, the shorter the distance apart .... larger the plant you buy, the wider.

I bought a non conifer for hedging as 5'x5' established plants and the planting distance for them was 3.5' apart.

sorry we couldn't help you how you wanted -- I think that in our own way we were trying to help, thinking of the footballs you could plant a nice thorny hedge --- to pop the balls! and stop the little horrors trying to get them back :o)