Substance underneath existing insulation - what is it? Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[Linda1982]

I was in the loft to do top up insulation yesterday. Underneath the existing insulation in between beams (not on them, they seem fine) is a white granule/crystalline salt like substance (like little tiny irregular balls). It looks like salt crystals but is very light. It's thicker in some places than others. After researching on the internet I think it may be a form of loose insulation filler maybe used prior to the 1st layer of loft insullation roll being put in. I have pictures.

Does this seem plausible? Is there any other thing that could cause a build up of this kind i.e. it has not been put down by someone but has accumulated after the loft insulation was put there? I'm just wondering if it may be harmful or why it may be there? Should I continue with the top up insulation?

Thanks!!

[kbrownie]

It will be loose fill or granular insulation, not uncommon, it's been made out of a few materials in the past cork and paper to name two.
It was normally laid at a depth of about 125mm, there is nothing wrong in topping this up to a total depth of 270mm, the one thing you should be wary of though, is electrical power cables, they should not be covered by insulation. It is best to have the cables either fitted above the insulation or laying above it.

[Linda1982]

Thanks I'll check for cables when I get back to it!

[kbrownie]

It's power circuits(socket/showers) that are the main concern, but check out the lighting circuits too, normally if they are protected by a 5A fuse or 6A MCB you will be okay, anything larger like 10/15/16A. Then it will need to be looked at.