New DPC and membrane, and dehumidifier question

[henry d]

My daughter has bought a house that needs a new DPC (tri-cream) and they are also removing 1.2m of plaster and adding a Triton platon PB2 membrane to the inside of the external wall before replastering.

Would a dehumidifier help when this has been restored to set the plaster and to dry out the old "wet" bricks and plaster? Any other observations?

Many thanks in advance!

[Sciurus]

Henry, the old rule of thumb is that it takes one month per inch thickness of wall to dry out naturally. I am guessing that your daughter has a solid 9 inch wall, which would take about 9 months. If it was a cavity wall, then it would take approx 4.5 weeks to dry out naturally.

The builder is putting a 1.2 m high membrane  (4ft) on the wall and then plastering over. The membrane will stop any residual (& new) dampness coming into contact with the new plaster. However it will also stop the dehumidifier from drying out the original damp in the brickwork. This is not a problem. The dampness can still evaporate to the outside (or into cavity).

This means that there is only approx 1 inch of new plaster to dry out naturally or with a dehumidifier.

In short, it should be fine to use a dehumidifier, which will dry out the new plaster and let the brickwork  dry out naturally. Once the dehumidifier has dried the plaster, it can be emulsioned, but it is generally recommended that it isn’t wallpapered for 6 months to be on the safe side.

It won’t do any harm to check  this question with the contractor.

[henry d]

Yeah, cavity walls. Many thanks, this is something I have never had to deal with before thankfully!

[tonker]

Henry, don't dry it out to quickly (cracking) My daughter has just had the same done it'll be dry in just over a week anyway. I'D have done it for them myself but they want the paperwork for 25yrs so they can resell in a year or two.

[henry d]

Thanks, my concern was not for the plaster etc but for her health, it seems dry enough its just the bulged plaster in a few places that rise up 2-3 inch up the wall that indicate it is a bit damp and I didn`t want her to be affected by it.

Thanks again guys I`ll check with the DPC guys/plasterer as well.

[figgy]

Mechanical heat recovery system for ventilating the house will help with keeping internal damp under control and any damp in the walls will dry out naturally.

Edited October 17, 2018 by figgy

[Yellow Bear]

42 minutes ago, figgy said:

Mechanical heat recovery system for ventilating the house will help with keeping internal damp under control and any damp in the walls will dry out naturally.

Or if this is not practical straight forward PIV