we power wash them ourselves, the last big one we did was in Bristol last year, was about 6000m2, they wanted it waterproofing aswell so we washed it and then taped all the laps prior to applying 2 coats of liquid rubber, the client supplied all the edge protection and the netting, they also had someone on there prior to us getting there to replace any damaged panels, skylights and tighten all the fasteners. depends what sort of result they want, if they just want it tidy rather than waterproofed then its just a case of power washing and then spraying. that was about £13pm2. can only spray at night or weekends as you dont really want a bill for overspray on cars in the area. call the office on 01492 544777 and ask for Phil White, we will be glad to help
