The turning circles will vary quite widely depending on the size and type of lift truck being used.
As a rough guide conventional counter-balance trucks would require an aisle width of between 3.5-4.5 metres. Reach trucks would normally operate in aisle widths of between 2.7-3.5 metres. There are other specialised warehouse trucks which can operate in aisle widths as small as 2.0 metres.
Many of the large lift truck suppliers are happy to offer support and advice when determining warehouse layouts.