Hi, I'm having difficultly in a flat I'm privately renting from damp issues, possibly condensation but after doing everything (heating, ventilating, dehumidifiers etc) not solving the issue, so I have just purchased a 4-pin damp meter.

http://www.ebay.co.uk/itm/310818252269?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Sadly it has no instructions on how to interpret the readings and searching the net seems to leave to leave me confused although I did read this somewhere:

Normal (< 10% to 16%), attention required (16 - 20%) and Action required (20-28%).

Is that accurate and how would this testing equipment really fair on walls?

I have taken a few readings with the walls I'm concerned about and it ranges from 20 - 26% even from top to bottom, I took a reading in a room not so bad at around 10-12% top to bottom.

Thanks for any help you can give me.