Measuring for moisture/damp

[JustMe]

My basement was tanked and converted about two years ago by professional builders.

Since that time I've *seen* no indication of damp. All the white-painted plaster looks as white as day 1 and there are no obvious indicators (mould, moisture stains).

However a piece of cardboard left in the room for a few days will get slightly soft, compared with another piece left elsewhere in the house, which suggests to me that the air might by moist.

The basement is about 60% below ground level. It is heated via central heating radiator as required for human comfort, there's a vent in the one window at one end and an extractor in the adjoining en-suite (separated by brick wall and not directly adjoining (via small corridor and 2 doors).

I want to move my bedroom in to the space but fear health/clothes damage consequences caused by damp. How do I measure the atmosphere to confirm if all's well? I've seen probes that test dampness in wall surfaces, but that shouldn't be at fault if tanking was successful.

I've thought about renting a dehumidifier to ensure no remaining damp, but I need a reference before and target after to know if there is a problem now that requires action and whether its a recurring problem, further down the line.

Can anyone offer advice?

TIA.

[Harry Bloomfield]

on 10/05/2008, JustMe supposed :

Many of the cheap weather stations include a Relative Humidity gauge for indoors. Maplin probably sell them.

If the walls seem OK, inadequate ventilation might be the cause. A dehumidifier would certainly help.

[stuart noble]

A simple hygrometer will give you the relative humidity figure

[N_Cook]

If you want to make a dampmeter, borrow or buy a digital voltmeter. Get a couple of pop-rivets (hard steel pins) and grind the ends to points and squash/clamp the rivet parts in between 2 bits of soft wood, with the pins about 1 inch apart.

Connect each pin to the voltmeter and set on the resistance scale and push the rivet pins against the plaster. Reading on meter scale and corresponding dampness for brick/plaster

10M , 1% 1M , 2% 100K , 38% 10K , 50%

M= megohm , K = kilohm, interpolate for actual reradings

-- General electronic repairs, most things repaired, other than TVs and PCs

Devices, Southampton, England

[meow2222]

Just bear in mind damp meters actually measure resistance, which is not reliably correlated with wall moisture content.

NT

[stuart noble]

Plus it's not what the OP asked for.

[N_Cook]

professional

white-painted

Very true. I knew of someone with a house with interior walls constructed of breeze-block with some conductive material in the composition. Someone fitting an over-picture lamp managed to put a mounting screw through the mains cable - lamp worked perfectly ok. The other side of the wall was the bathroom and someone placed their hand on the wall while in the bath

The OP knows there is damp in the air from the cardboard test So pointless monitoring the air humidity, more a matter of tracing where the "tanking" is flawed/breached.

-- General electronic repairs, most things repaired, other than TVs and PCs

Devices, Southampton, England

[stuart noble]

It may not be flawed/breached. There may just be insufficient heat/ventilation. The OP mentioned "radiator" in the singular, which may not be enough.