How to help plaster dry

silvercar

I have had some plastering done. Mostly skimming of the walls and ceiling. There is a boiler in the room, but no radiators at present. So the heating is minimal.

I have a humidity measurer in there that has shown the humidity between 77-85%. I did open the windows in order to get some fresh air to circulate, but looking at the weather app, the humidity outside is currently showing 93%, though it will drop during the day.

I can't open the door to the rest of the house as the air from that room seems to irritate (dust I guess). Is it best to have the windows open or shut, or should I be comparing the outside and inside humidities?

glennevis

You need a dehumidifier.

I had to dry out a damp flat last January and went for an Ebac 2650. Left on in smart mode it took two days until it had the humidity under control. I seem to recall I emptied the container about 4 times. Then it just came on occasionally to maintain ~50% humidity.

Uses ~120W when in use, so less than 2.5kWh per day. That compares with my Meaco which uses ~350W when in use but I use that in my garage because it works down to 0°C.

I've no connection to the company, just a happy customer.

ETA: Close the window unless you want to dehumidify the planet :-)

silvercar

I don't have a humidifier and won't be around to empty the tank, tbh we are not in a rush, I just wanted to know if it is best to open the window or not. High humidity outside vs increased ventilation.

stuart45

The relative humidity outside will probably be higher due to the colder temperature. You will probably find that getting a bit more airflow will help the plaster dry out.

ThisIsWeird

Open the windows. Windier the better. It's a shame you cannot get a through-draught.

Slinky

If you can't remove the water through using a dehumidifier, the only other option is out the window. 

I recall standing in our soaking wet plastered house in the week before Christmas, with the windows wide open and howling winds, and no heating as the radiators had been removed. It was the lowest point of that particular build

silvercar

ThisIsWeird said:

Open the windows. Windier the better. It's a shame you cannot get a through-draught.

Brill! I wasn't sure if the high humidity outside meant I was better off shutting all the windows. I have a couple of windows open and the internal door to the garage. Garage door is itself a bit iffy, so I'm sure it isn't sealed.

Slinky said:

If you can't remove the water through using a dehumidifier, the only other option is out the window. 

I recall standing in our soaking wet plastered house in the week before Christmas, with the windows wide open and howling winds, and no heating as the radiators had been removed. It was the lowest point of that particular build

I get the science. I wasn't sure if the water within the plaster would move to be water vapour in air in the room and that would be a better option if the humidity outside was higher.

stuart45

It depends on the temps inside and outside. If it's 5c outside, even if the R/H is 90 there won't be as much moisture in the air as inside where the R/H is 80, but temp is 20c. As the outside air warms up the R/H drops to lower than inside.

ThisIsWeird

Hardly ever ever ever will the outside humidity add to that of a room of drying plaster.
For 99% of the time, providing as much outdoor ventilating as possible will greatly aid drying.

stuart45

The other 1% have got HVAC systems.

DRP

Get a fan and open the windows a crack. One of those ones that moves to and fro to blast air in an arc. 

That’s what I’ve always done