Mould at ceiling edge

I have seen a lot of mould at the edges of ceilings, especially where the wall is an external one. So what is the cause of this?

There are a number of potential suspects:

  1. Lack of ventilation
  2. Water ingress from leaky roof / blocked gutters
  3. Lack of insulation

1. It is unlikely to be lack of ventilation, although poor ventilation in higher humidity rooms (bathrooms, bedrooms, kitchens) can make the situation worse.

2. Water ingress can be another source of damp and hence mould, but here the mould tends to follow the water, so will head down the walls as well. It is worth noting that gutters should be checked regularly to ensure that they are working properly.

3. Lack of insulation is the probable culprit here. Cold spots caused by a lack of insulation makes the surface cold enough for the mould to grow nicely. Insulation, especially in the eaves, is notoriously poorly fitted. It is already the area in the loft that has the lowest level of insulation due to the junction of roof and ceiling, but it is also tricky to fit, so many people find that it has not been done properly.

So we would recommend having a look in the loft space and checking that the ceiling is uniformly covering the it. I would also ensure that it is as well insulated as possible in the eaves (whilst remembering not to block them as this could cause other ventilation issues for the loft space).

Once the insulation is correctly installed, treat the mould with Auro Anti-Mould Treatment and then you should have a permanent solution.

As an aside, I once found a mould patch in the middle of a bedroom ceiling. No leaks etc, just a odd spot of nasty mould. A quick trip up into the loft found that the insulation had been installed really badly and there was a bald patch that correlated exactly with the mould in the room. Thankfully there can be easy solutions to what can appear to be major problems with houses!