On Wed, 5 Aug 2020 20:07:23 +0100, TimW wrote:

I used one on an old boat some years ago to dislodge barnacles and
everything but had to stop when it started to delaminate some of the
fibreglass.

B-) Even a small pressure washer can be pretty vicious, especially
if there are any nooks and crannies for the jet to get into.

Not all pressure washers are the same. A £50 lidle tool is unlikely to
help. You might hire a petrol powered one.

I used a "medium" sized domestic Karcher with the rotating needle jet
at about two inch range. 1.4 kW, max 100 bar, 5.5 l/min it says on
the label. To save hoiking it, mains and hose up the scaffolding I
got a 5 m high pressure extension hose.

--
Cheers
Dave.