On Tue, 29 May 2018 10:40:04 +0100, RJH wrote:

On 29/05/2018 10:29, Harry Bloomfield wrote:
Scion pretended :
Getting to the outside of the wall is not an option so I've been
reading about tanking. Seems like there are a few gotchas although the
sites I've read are all companies that can do the work...

Water ingress cannot be sealed from the inside, pressure will simply
lift off any sealant used. It has to be done from the outside.

The only fix on the inside, is to allow it to collect and to drain it
away, with a waterproof membrane spaced away from the wall, to provide
a dry interior surface.

A bank vault I was involved with had a drain cut all the way around,
which led to a sump and a pump.

Much as a cellar conversion. I'd suggest the OP gets a quote or two -
should provide some ideas on approaching the issue, and it may turn out
cheaper than they expect. I asked on a local forum for recommendations.

I'd consider it quite DIYable, but it has to be done properly, with the
right materials.

Thanks for the comments, people.