This is a regular question, so let's see if we can get some hard answers from those experts who do the jobs regularly.
Assume that the three conservatories below are caked in algae, there's several years worth of dust on the roof, the ends of the roof panels are solid black and the gutters are full of crud. They look embarrasing!
How much would you charge for a total clean, outside only.
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No 1 - Victorian 5-facet, polycarbonate roof
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No 2 - Lean-to, self-cleaning glass roof. Regular glass sides down to ground.
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No 3 - Victorian 3-facet with box gutter, Polycarbonate roof (six sections on box gutter at rear) This one has difficult access at both sides as the side clearance to the fence is just less than 5 feet.
You've just about got enough room at the sides to get your step ladder or doubles in place. The problem is that you're using your pole extended to 12 feet or more and you haven't got much room to manoeuvre it.
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And if you're up for it, make an estimate of how long it might take you to do the job from arriving to driving away.
Remember, they are really dirty!!!!!!