No. If you are using 4by 2 then they will only span 4feet between supports.
Between the timber and the support ( concrete block of paving slab) there should be a DPC ( damp proof course) this stops the timber getting wet and rotting.
Between the timber and the support ( concrete block of paving slab) there should be a DPC ( damp proof course) this stops the timber getting wet and rotting.