Dehumidifier

Mojo29

I’ve been having a bit of a problem with a wall that was suffering from penetrating dampness caused by rainwater coming in through a damaged chimney stack. I had the stack completely taken down and the roof modified to “felt” and slate over the old chimney. This was done at the end of July.

Despite the dry weather over the past three weeks (bar Monday) the walls internally don’t seem to have dried out at all.

Can anyone recommend whether a dehumidifier would help me dry out this wall (the breast is inside the cavity and it’s only the internal wall that looks damp)? And if so am I better off buying one or renting one?

Looks like you can get decent refrigerant/compressor ones for £75-£130 but renting one is £130 Ish for a week.

Paula_Smith

Do you know the walls have not dried out or do they just look damp?

You can get a damp meter for just over £20.

cheap-information

I'd get a Meaco Platinum and just leave it on set at 55%, will turn on whenever it goes above and will be off at all other times. Uses little electricity compared to others also

FreeBear

Paula_Smith wrote: »

You can get a damp meter for just over £20.

Just bear in mind, these meters are designed to test moisture levels in untreated timber. They can not be relied upon to give any accurate readings on bricks, plaster, or painted/treated timber. The chemicals and salts will throw the readings out.

That said, if used correctly, these meters can be used to give a relative indication of damp if (and only if) measurements are taken from very similar areas.

Mojo29

Paula_Smith wrote: »

Do you know the walls have not dried out or do they just look damp?

You can get a damp meter for just over £20.

I know the walls have not dried out because I open the windows and set the fan heater on it for a few hours and it is visibly dryer.

I then switch off the heater overnight or when I go out and when I come back a few hours later the walls are wet again.

I know that damp meters don’t necessarily work for hydroscopic salts so don’t see the point as they aren’t reliable.

dunroving

I don't know if it is any help, but I can tell you my experience with dehumidifiers (see my recent post about concrete floors and DPM for some background).

Three months ago, I had an internal leak - cistern broke and was trying to continuously fill for 6 hours (calculated 2,500 gallons of water, although much of it went out of the overflow pipe). Most of the internal leak ended up in the kitchen and via a connecting door, to the living room.

The loss adjusters sent a company to tear up all of the carpet, and they then installed a large dehumidifier and two large fans. 5 weeks later, they issued a drying certificate, though I haven't seen the readings they obtained. The Marley tiles were subsequently removed, as they were found to contain asbestos (so, notably, the concrete floor was covered by Marley tiles during the drying.

The dehumidifiers are now back, because I obtained several relative humidity readings > 90% from a hygrohood placed on different parts of the floor.

Unlike last time (when the drainage tubes were routed into the sink drain), this time the tube is routed into a 10-litre canister. After running for approximately 48 hours, I've emptied the canister 3 times, and would estimate this corresponded to about 25L of water. So, yes, they do seem to work, but my guess is you will need to run them for a long time.