Why is this ceiling mould in a line? [pic]

[LimeWire]

We're long-term renting a house that's super damp (1890s semi on the coast).

We're used to de-moulding corners in the bathroom etc. But why on earth is this mould forming in a line on the ceiling? I can't seem to work it out. Anyone else had this?

FWIW we keep windows regularly and keep low heat on all the time for ventilation.

Go and look at the corresponding floor above.

Is your or shower above it?

Bath or shower*

Leaking pipe in the floor above?

Even if your shower/bath isn’t directly above it, it’s probably where your pipes run. There’s likely a slow leak and you’d need to lift carpet/floorboard upstairs to find out.

I’d get your landlord in.

Ahh that would make sense. Above this room is the loft but we aren't allowed access to it. Every time we've complained about mould in the last few years, we've been blamed for inadequate ventilation. So I'm concerned he'll just get mad at us again...

Luckily we're moving out in March :) Maybe we can mention it then?

There might be a gap in the insulation above creating a cold spot.

Looks like leaking pipes on the floor above to me.

Don't leave it until March to mention it; your landlord will probably try and deduct it from your deposit, and then there'll be a to and fro while you argue the toss. I'd tell him now.

The bathroom extractor fan doesn’t vent up there does it?

My house has lines like that where the rafters run in the attic and the insulation has a gap.

That doesn't look like a leak but a cold spot where condensation collects. Keep it bleached until March if you're moving out.

it looks to me more like a leak than a chill shadow mark.

there might be a pipe lying against the ceiling, but those straight stains often occur when a ceiling has been plasterboarded, and leaking water penetrates through the joint where two boards meet (even though the joint has been hidden by plaster). The boards are (about) 8 foot x 4 foot, and once you know, you can often detect marks or cracks following a pattern around the boards.

Especially with modern foil-backed plasterboard, which has aluminium foil on the unseen side, which will hold back minor leaks for a while.