Hi all! Hope your well! Not posted here for years but I’m hoping you can help!

Ok so, in my 150 year old terraced house...

Only my front room has a suspended floor for some reason?

So it’s time to insulate! I’ve lifted the boards and it’s 2 feet void straight down to soil, the stone walls / foundations around the perimeter are external walls( 2 external walls two internal walls)

I’ve had a good look around, no cables , no pipes, doesn’t seem to be any evidence of any vents, just foundation walls straight down to floor, there was a 6x6 inch vent outside the front door but this just seems to be placed into the render outside and doing absolutely nothing, no evidence of this vent inside either.

The wooden joists are sat on little stubby walls, the joists are dry, the stubby walls are dry, the soil floor is dry, the only mildly damp areas are the two external wall foundations, but I think this is just because the pavement outside is 2 feet above the depth of the suspended floor.

My external walls have been pebbledashed over stone which I am slowly removing to dry out the walls!

But yeah, it’s a hell of a lot dryer than I expected it to be! Maybe because it’s just floorboards with gaps in?

So I’ve done a search here, and I like the idea of just tipping beads in and plopping the boards back down, but is it as simple as that? Was hoping to tip them in right up to the top of the joists and then replace boards?

If I totally fill the void then there is no void, and in theory doesn’t need ventilation? Is that right?

What if there’s a fire? Will these beads under a wooden floor be super dangerous or not?

But my main concern is the damp walls, only the two external walls down there are damp, gotta be because the pavement outside is 2 foot higher, but I cannot do anything about that, so if it gets filled with beads what will happen to these damp walls, will they just stay damp and get along with the beads or will the beads increase the damp somehow? This is the bit I’m unsure of, I would hate to fill it and then find out it’s made it worse!

Also if this is the way forward how deep does it need to be, I’ve got a 2 ft void, do I fill it totally with beads or can I build up with hardcore or sand then the remaining gap with beads? I’m hoping you can help it’s frying my little brain! Cheers guys!

Cheers Tony! There’s bags of beads on eBay, flame retardant but they are £250! How do I figure out how much I need? Also do I need to add a vapour control sheet under the boards before they go back down?

Cheers for the help sir Tony! Does the vapour barrier have to be something special ? Or is it just a plastic sheet?

Am I showing my ignorance ?


If there really are no vents into the space will you benefit.

Static air is a good insulator in it self

hang on while I find my bullet proof vest