I have just bought a very wet house! Semi detached about 100 years
old. I've taken some steps to try and cure what I thought the cause of
the problem was i.e. removing the 12 inches of concrete that encased
the building above the internal floor levels, fixing drains, removing
3 feet of concrete render along one side, gutters etc. It subjectively
feels much drier even after only 4 weeks.

Knocking off the damp plaster throughout to about 1 to 1.3m reveals
that the bricks have been injected at some point in the past. I wasn't
sure what else needed done, so Rentokil sent along a surveyor today to
have a look. He drilled a hole in a wall, put the dust in a flask type
thing and showed me that it was 10% (apparently 4% or above is a
problem).

He's suggested 2 things;
1. Injecting the mortar just above floor level throughout, cost £1200
(exc VAT)
2. Getting Rentokil to plaster as well, with 'special' plaster that
will repel the water still in the damp bricks, cost about £3000 (exc.
VAT)

He says that if I put normal plaster on the walls without letting them
dry out, the new plaster will crack and fall off. A little research
suggests two alternatives to rather expensive Rentokil plastering;

1. Cover walls with PVA and then apply plaster with 'waterproofing'
mixed in (what is this waterproofing bit?)
2. Cover walls with cement render, which I'm told is waterproof, with
added benefit of adding support to slightly dodgy brickwork.

Does anyone have any advice for me on these points? It is probably
clear that my building knowledge is limited, so please assume I know
very little if you reply!! Whilst the house is a building site it
would be great to get this all sorted, and not have to worry about it
in the future.

Thanks in advance for any assistance, Ellen