What might cause mould on soffits?

mouthscradle

We've had a first viewing on a house and have booked a second viewing for this week. When there I noticed dark patches on the white roof soffits on the front of the house, like mould. You can also see it on the agent's photo, see below (I can't get it any more zoomed in and clear unfortunately, but you can hopefully see what I mean).

http://smg.photobucket.com/user/harm_of_will/media/Screenshot2014-09-22at142008.png.html?sort=3&o=0

I know nothing about roofing but have had a bit of a search online, and have read that a possible cause could be a lack of soffit vents and loft insulation that goes right to the edge of the roof blocking any ventilation. Have I interpreted that correctly? The EPC says the house has 200mm of lost insulation so that could be it.

Will get my husband up in the loft to have a look if he can at the second viewing. What other symptoms of lack of ventilation might be apparent, moisture on surfaces in the loft? What else could cause this issue that we could try and look out for?

I'm sure it's not a big deal but would like an idea of how to spot whether the cause is something major or minor.

G_M

well you don't need to worry about damp or moss etc on the outside - it's inside that would be a problem!

Many roofs etc have growths on them. Provided it is not extensive and interfering with the run off of rain its not an issue, unless you consider it unsightly. In which case, clean it off.

And since it appears to be plastic, just pop up a ladder with a sponge and give it a wipe.

If it was wood, then re-painting would be advised to stop the wood rotting, but even then it's non structural so hardly a reason not to buy a property.

WestonDave

The moss on the roof suggests that's the cooler side of the roof (north facing?) and if so its not unusual to get a bit of growth tucked away in a sheltered spot. I suspect its just surface and will wipe off. By the looks of it you could do it from the bedroom window.

mouthscradle

Thanks guys, I did wonder if it was lack of all day sun (this is actually the west facing side). But on driving along the road looking at the others, that all face the same way, this was the only one showing the mould. So that makes me wonder if this house has something more going on.

Bluebonnie

Possibly not mould, but paint flaking off.

The windows seem to have replacement upvc frames, so it could be many, many years since someone has been up there with a paint brush.
(Even if it was south facing, the sun doesn't shine upwards onto the soffits.)