I have noticed mainly in the corners of the upstairs bedrooms which are slept in, watermarks which run down the wall (external facing). There is nothing on the ceiling or outside. The other empty rooms appear fine. It does in one room though extend across the ceiling line down the wall above the window about 10-15cm. It is quite faint. I noticed it was slightly damp to touch in the morning then dries out. It has not rained recently either. We have had condensation problems since we moved in to the point water was streaming off the windows area and now have black mould around the edges. We purchased a dehumidifier which we put in the landing. Cannot see any issues with guttering/soffit. It is worse when it is particularly cold.

I am hoping it is condensation and we were thinking of painting the rooms with similar paint to our bathroom, water resistant, mould resistant stuff. Will this work? Just noticed its getting bigger.

 

Welcome to the forums!

It sure sounds like condensation. A bath rm paint should help, be sure to wash off any mold/mildew [and cleaner residue] before you paint. Are there any brown stains from the moisture?

 

yes very light brown at the edge of the waterstain

 

Water stains almost always bleed thru latex primer/paint. You'll need to coat the water stains with an oil base primer.