Get the concrete scrubbed clean, then cover with hot poured bitumen,
with a top covering of bitumen felt similar to what is used on wooden
sheds, but heavier grade.
A more expensive option would be to add a pitched roof over the top of
the concrete.
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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
Just get the concrete clean first so it can key to it.
>We have an old Levensulme air raid shelter in our garden which is used as a
>shed - brick built with a concrete roof. The roof has started to leak.
>What would be the best way to fix and waterproof this?
Drop a bomb on it.