I live in a 1930th house. Some years ago I noticed a light brown line under the rsj towards the bay window in the lounge. Over time the line has become even lighter. Last week I noticed the line under the rsj in the kitchen. The extension was built 7 years ago. Near the line the paint had been slapped on very thickly and is coming loose (very small are). The plaster underneath is dry. Both lines are in the middle of the rsjs. Any ideas. Unfortunately, I am hopeless at DIY.
