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How to work out damp plasterboard is actually drying out after a repair

Postby Jacob123 » Sun Nov 14, 2021 6:57 pm

My question is how can I work out damp plasterboard is actually drying out after a repair and when can I paint?

I have had water seeping into my bathroom ceiling for over a year. After a couple of attempts I think my roofer located the problem, the mortar on the coping on the parapet wall, and has fitted a DPC and repointed.

Here is a picture of the bathroom ceiling:
bathroom-ceiling-14Nov.jpg

And here is a picture from the loft where the water was working its way from the brick on the right, through the old timber wall plate onto the plasterboard below:
loft-20-oct.jpg


I have a £20 damp meter with pins but after three weeks the readings are still off the scale. Is there a more accurate damp meter that is not hundreds of pounds? or is there a simpler way to tell if it is drying out?

And how long do I have to leave it before painting?

Thanks
Jacob123
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Postby stoneyboy » Mon Nov 15, 2021 11:30 pm

Hi jacob123,
Stick with your pin damp meter. Check away from the damp patch and you should find a low reading, plot the edge of the area where you are getting full scale readings and over time see if this reduces. If not you have not solved the problem.
Regards S
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Postby Jacob123 » Tue Nov 16, 2021 12:33 pm

Thanks stoneyboy. Actually drawing it out on the ceiling is a really practical solution I had not thought of!

Any views about how long it should take to dry out naturally? Three weeks sounds like a long time but it is a bathroom and I understand plasterboard can soak up a lot of water.

thanks

Jacob
Jacob123
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Postby stoneyboy » Tue Nov 16, 2021 9:41 pm

Hi jacob123,
It wouldn’t surprise me if it takes 3/4 months if you want it to dry naturally. If you have a heater in the bathroom leave this running for a few days and see what effect this has. Bear in mind that the dampness will be self sustaining - a damp ceiling will be cold due to evaporation but the cold will lead to condensation.
Regards S
stoneyboy
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Postby Jacob123 » Tue Nov 16, 2021 11:00 pm

Thanks once again!
Jacob123
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