If it’s going to take a day, then charge a day rate plus £20 for the faff and mess.
I don’t offer to re sand anymore, but if you do, charge for it, as it’s a right nuisance going back the next day and sweeping sand about.
I did a patio the other day, medium sized, took 4 hours and was £180. Then did the windows at £20. I price it on a day rate because I just know from experience I won’t be doing any other work after pressure washing, even when’s it’s only taken half a day! It’s a messy faffy job with more packing up to do, so I just want to get home after!
So price high unless your desperate, that way it’s a good little number.
I’m using a 21 lpm machine, speeds it up no end.