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Condensation inside a cavity wall

Postby DoingItMyself » Tue Dec 16, 2008 10:31 pm

Hi, I am part way through converting a single storey, single brick shed that is attached to my house. I have created a 50mm thick internal cavity lined with 12mm plaster board, and installed foil coverd bubble wrap in between the brick and plaster board as an additional method of insulation. I have yet to finish plastering the plasterboard. However, I have recently discovered that condensation is forming on the inside surface of the bubble wrap, to such an extent that water is running down the foil and seeping into the room below the plaster board. (I was able to remove an electrical socket to see inside the cavity). My questions are: Will I be able to stop the passage of water through the plaster board once it has been painted? and if so will I end up permanently trapping water within the cavity?
Is there anything I should consider doing to remove the formation of condensation within the cavity? :?
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Postby welsh brickie » Wed Dec 17, 2008 2:33 pm

You have used the wrong insulation really,The moisure will hold in the cavity,It would have been best to use sprayfoam insulation in this instance.
The way to combat the moisture is to put airbricks in the external wall creating airflow to dry out the moisture.
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Postby the specialist » Wed Dec 31, 2008 11:23 am

Sounds to me that if moisture is running down the internal surface of the insulation that it is condensation and not penetrating through the brickwork. Firstly I think you may have needed more insulation but this type of insulation is a vapour barrier. This means that the internal moisture can not diffuse through it. All you need to do is heat the room properly which will mobilise the moisture into vapour and then vent it out either through a window or install an extractor fan.

You also need to ensure that the single leaf of brickwork has a dpc and that it is resistant to water penetration laterally. You could apply a waterproof sealer externally.

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Postby TheDoctor5 » Fri Jan 30, 2009 9:58 am

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