how to dry a very damp brick wall (after failed steam cleaning of exterior)

7 May 2009
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United Kingdom
Hello - please, please can anyone advise how to dry out an exceptionally wet brick wall? The source of water was fixed 2 years ago. You could call this a tragi-comedy....

We wanted to remove the paint from one exterior wall to leave the original bricks. Our "builder" recommended a "specialist", who tried one thing after another, including various acids (which hurt his hands and destroyed some of our sandstone. Don't ask). He eventually decided the best bet was pressurised steam cleaning using his compressor. This didn't shift the paint very well, although it did remove most of the top layer of acrylic paint, a good thing.

After 6 weeks he gave up. Soon the plaster started falling off _inside_ the wall for the full two storey height, and we realised he had pumped lots of water and steam under pressure into the wall from outside... and forced out a lot of mortar from between the bricks. It seems to be a solid wall, quite thick (> 40cm). Built to high standards in 1901 to house the carriages of a local stately home.

We scraped off all the exterior loose paint and mortar and re-pointed with lime mortar. We removed all the paint and efflorescence on the inside walls and any loose plaster. We open the windows at every opportunity. Over 2 years the wall has become drier and smell of mould has almost gone. The wall is mostly old lime plaster with some modern patches. The gypsum plaster has dried from deep plum coloured to pinkish white, so we have progress...

A surveyor last week said the (plaster in the) wall still has a 60% moisture content. I know such meter readings are dodgy but it seems it is still very high, and I am unsure how to get the levels down further. Will a dehumidifier help? We haven't used the rooms for two years (it's a master bedroom upstairs (20 ft square) and living room (20 x 35ft) downstairs. They now seem habitable. Do I need a really powerful de-humidifier? The wet wall is 20ft wide and ceilings are 9 feet. The house is centrally heated but cold (typically 12-16 degrees).

Oh, and the builder said it wasn't his responsibility ...

How should we try to dry these two rooms? The damp is basically on the one wall that was cleaned and about 6 inches around the corners.
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Open windows and big fans are generally more useful than dehumidifiers when there is a lot of dampness, unless the weather is very wet or cold.
thanks for the quick response... i hadn't thought of fans but we've opened windows as much as possible...
Keep the room warm, and use a dehumidifier......expect to remove about 4 litres a day with a domestic machine.
They don't like working in cold conditions though.
John :)
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Its the warmth that evaporates the water, the dehumidifier, just cools the air going through it, so the excess water condenses in it and is not recirculated. So with a dehumidifier, heat on, windows and doors closed. Cheaper just to use fans and a slightly adjar window.
Keep the room warm, and use a dehumidifier......expect to remove about 4 litres a day with a domestic machine.
They don't like working in cold conditions though.
John :)
Desiccant ones do. I know, we have one and it did well in our conservatory last winter.

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