Would you spray it on and jet wash off or jet it first to get rid of thick then lay it down. My front and back patio.
To be honest with those flags you don't need to use a pressure washer at all if you did not want to or don't have one.
All you need is the following:
1. an outside tap, hose reel long enough with adjustable fan nozzle on the end.
2. a deck stiff scrubbing brush
3. window cleaner’s oblong bucket or painter oblong pale
4. one 20 litre container of sodium hypochlorite 14-15%
5. chepo telescopic car brush (can just use the brush and screw it onto a 5m harris pole if you like as then comes in handy for applying hypo on wall too)
6. wear old clothes
7. eye protection
8. decent rubber gloves
9. wellies
How to apply:
1. give the area a quick sweep
2. wet down with the hose any run off areas like grass, plants, shrubs, boards etc
3. wet down the slabs
4. roughly half fill the oblong bucket with tap water
5. top the bucket up with hypo so you have roughly a 7% mix - were gloves and eye protection as if it splashes in your eyes you will know about it and try not to splash it on your old cloths too.
6. slap the hypo on with the car brush & use the stiff deck brush to adjitate.
7. try not let the area dry out and apply more hypo on bad areas if need be.
8. allow enough time at least 20 mins to let the hypo do its magic
9. rinse down with a hose including soaking grass etc again just to make sure.
Job done
Warning: Keep pets, kids and adults off the area whilst still wet and don't let anyone including yourself track hypo into your house. Do not use hypo anywhere near a pond for obvious reasons.
Pressure washing will blow out lose pointing so that's why on some jobs I just use hypo otherwise on bad pointing it just looks a mess afterwards. Hypo will kill the algae and any black spots so will look a lot cleaner than if just used a pressure washer.