Damp and moisture can be a real headache for home owners. Often large scary looking marks, on walls or ceiling, are easy to combat and on the other hand the hidden ones such as dry-rot or rising dam which might appear small can mean serious problem. All starts by correct diagnosis. I must say it's not uncommon that even paid professionals make mistakes when reading their instruments. Even the most expensive measuring equipment is only half of the help, without practical experience and technical knowledge. Often old rising damp or wall already dry leaves salt residue in bricks and mortar, that can be read by electrical resistance measuring instrument as high moisture content. Therefore, more extensive survey is needed such as drilling deep hole and measure moisture in the drill dust or inside the drilled hole. Black marks on wall or ceiling are usually condensation which happens a lot in winter season. Traditional english houses don't have a good insulation, so when you put together cold walls and high moist, warm air inside the room you have the perfect combination. Exactly the same what happens on your bathroom mirror after hot shower. So, to tackle condensation, the easiest and most effective solution is a good quality and size dehumidifier. I don't want to go into too many details as this article would cover couple of pages, my aim is to talk about this problem and give you some basic advice how you can investigate this issue by yourself and at least understand the difference, and when you really need to call an expert and also understand the report you should receive. Please send your comments, question or even photos with your situation so we can talk about it and help you with it.
Ideal room temperature should be between 21-24C with moisture content between 40-50%