Advice on suspended floor and bare ground underneath

[JayW]

Hi All

I am planning on insulating my suspended living room floor with PIR boards however upon lifting a board to investigate and come up with a plan I'm greated with the following.

I was hoping it was a concrete oversight which I could sweep and clear up to aid ventilation etc but it appears to just be a sandy / soil base with a slight crust to it. If I scrape or poke enough I can disturb and go through.

It's also covered in what I thought was mould / mildew but I'm unsure now if this is just salts and nothing to worry about.

Im unsure now if I should be worried or if I should be looking to add a concrete base or DPM sheet / gravel?

Or do I just ensure adequate ventilation from air bricks and continue to insulate with PIR and leave the floor alone.

Appreciate any advice

Thanks

 

[conny]

I would nail/screw some chicken wire to the undersides of the joists and drop your PIR, (or other chosen insulation such as rockwool), on top of the chicken wire basket then relay your floorboards.
Let the air circulate underneath by the use of air bricks, (if none already fitted), to avoid damp issues in the void.

 

[John D v2.0]

If there's no issue now, just make sure the ventilation is clear, and go right ahead.

 

[JayW]

Thanks for the replies.

The house has air bricks that are all clear. I was just concerned by this white substance and if it's harmful to us or the house.

I can always increase the ventilation if needed but aside from the white substance and musty smell the joists etc all look dry and clean.

Thanks

 

[John D v2.0]

The crusts will just be whatever was dissolved in the moisture that is evaporating, could be salts or limescale or whatever, but it won't hurt anything

 

[oldbutnotdead]

Its generally worth chucking DPM under there to reduce the amount of water vapour coming up from the ground- gives the air bricks less work. If you can get some in there without too much effort then do it, make sure there's minimum 150mm between top of whatever you use to weight the DPM down and underside of joists