I was almost put off purchasing this item by one previous very poor review,but after using the cleaner a couple of day,s ago I can only assume that the cleaner tried by that reviewer was faulty.
Having spent a lifietime in engineering I am familiar with all kinds of commercial equipment so I can write on this with some authority.
1)Easy to assemble.
2)My drive (blocks) had not been cleaned since laying 12 years ago and was black.
3)Switched my K4 pressure washer ans the the result was startling,immediately revealed was the original shades of red block paving,one slow pass was all that was needed,my drive has a gentle slope to a slot drain so little residue was left behind,i cannot fault ths cleaner.
I lent it to a friend who cleaned a block diveway twice the size of mine,block paths and a rear slab patio with same excellent result.
Worth every penny,i would assume it would work as well on decking and walls.