How to install under-floor insulation and prevent mould?

[matmg]

Hi

with the cold weather I’m looking to install some insulation under my floor. We live in a pretty old place and have wooden floor boards. Going under the house it seems like a simple task to install insulation. I’m looking at installing Expol Polystyrene insulation panels. My questions is about moisture. We seem to have a bit of moisture underneath our house and wanted to know if these panels would be effected by moisture. Whether they would grow mould after time. The floorboards sit anywhere from about 1meter to 40cm above the subfloor of our house.The difference is due to our house been on a slopped block. 

Floor boards don’t seem to be affected by the moisture. We have one room in the house that gets some mould on one of the  walls that has built-in wardrobe fixed onto it. 
thanks in advance for your advice

cheerd

mat

[JacobZ]

Hi @matmg,

Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.

Mould is certainly something to consider, but it shouldn't pose a problem if there is enough airflow beneath the subfloor.

The height of your subfloor is in line with the heights dictated by the National Construction Code. This combined with the fact you have no current issues with mould under your floor tells me you shouldn't have any problems.

If you are concerned, it might be worth checking periodically to see if there is any mould present.

Let me know if you have any further questions.

Jacob

[matmg]

Thanks Jacob.

just to clarify Wie have mould on some of the soil in the subfloor but there doesn’t appear to be any on the wooden floors underneath. There’s signs of rising dumpness on the subfloor bricks (footings) but it stops at a certain point and doesn’t get to the top where the footings meet our wooden floors underneath. Do you think there would be any issues with the insulation from a mould perspective. I read in the specs of this insulation that it’s no effected by moisture. Just to add we also have a fan installed underneath at the subfloor  to promote  airflow 

thanks 

mat

[JacobZ]

Hi @matmg,

Everything you're saying is telling me the house was built well and there is adequate airflow that should prevent mould from transferring from the earth to the subfloor.

If you're concerned, you might like to treat or remove the existing mould to prevent any kind of transfer. 

I'd suggest using How to get rid of mould as a guide on how to treat the mould or to remove the soil where the mould is growing completely.

If you choose to do this, please remember to wear a mask, as mould spores can become airborne.

The rising dampness in the brick piers will continue to the point where a damp-proof course has been installed. Typically, when the bricks are laid, a plastic material such as these Polythene Damp Courses will be installed at a certain point to act as a physical barrier that will prevent the dampness rising any further. 

Once again, it sounds like a well-built home that has already taken the steps necessary to prevent mould transfer into your subfloor. Nothing you've said raises any alarm bells for me. 

Let me know if you have any further questions.

Jacob

[matmg]

Thanks mate. Good advice