Dark marks on Ceiling

[WelshMoth]

Our upstairs ceiling was painted only a few years ago and already I notice dark marks - they seem to be the same shape as the beams/joists in the attic, and are long marks as opposed to random blobs IYSWIM.

What are these?

I have these stains too so I looked it up. It is called thermal tracking. It's due to dirty air and condensation, I think.

your loft insulation needs improvement.

Shadow staining occurs on cold patches of the ceiling.

p.s.

do you have open fires, or a person who smokes or uses candles?

Soot stains occur very quickly.

Thanks pinklemon and pigletjohn.

Piglet - no smokers and no open fires, but we do burn candles.

We also painted a box room a crisp white, exactly 4 years ago and for the last year, I've noticed what looks like a film of blackened soot (albeit a very light one, but very obvious) around the coving. Looks awful.....

Is this related to the other dark staining? Our house is about 17 years old and as dry as a bone, so am trying to understand where the condensation is coming from?

candles make soot. if you have a favourite spot for a candle, look at the ceiling above it and you will see a dark puddle.