On 27 Oct 2004 06:34:13 -0700, (Ellen
Rawlinson) wrote:

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

My architect has a big problem with these injection solutions, He says
it takes 10 years for the damp to rise 1m in a wall, so if you hack
off 1m of plaster, and replace with waterproof plaster, you need do
noting else, to achieive a 10 year solution.

There are tanking membrans that you can fit under plaster, I will fit
these to the walls in my house that have no DPC.

Cement render really needs a waterproofer, its only waterproof if its
made really strong, and then it srinks as it sets ..... There are many
available.

There are some electronic systems, I looked into one, but when I told
the sales guy building regs wanted to see the BBA cert for it, he ran
a mile.

I suspect you need a guy who knows his stuff to vist your place,
rather than a guy trained for 3 days in a classroom.

Rick