Insulating suspended timber ground floor

[mark482]

Since I have some of the floorboards up on my ground floor to do some sound insulation work and move a radiator, I thought I might as well add some insulation? It's a 1930's house, tongue-and-groove timber boards on joists, about 2ft cavity underneath. Can I do something like attach mineral wool between the joists? Would I use some kind of netting?

While I'm at it, under the floor is a long narrow "tray" of some kind of orange sawdust-like stuff. Is this some kind of damp-proofing??

 

[Deluks]

Since I have some of the floorboards up on my ground floor to do some sound insulation work and move a radiator, I thought I might as well add some insulation? It's a 1930's house, tongue-and-groove timber boards on joists, about 2ft cavity underneath. Can I do something like attach mineral wool between the joists? Would I use some kind of netting?

While I'm at it, under the floor is a long narrow "tray" of some kind of orange sawdust-like stuff. Is this some kind of damp-proofing??

Rockwool on chicken wire will work, but this is normally used between floors. It will be easier to cut rigid foam board or polystyrene and rest it on some battens. The rockwool will be cheaper though, you can get it in rolls.

Maybe the carpenter who installed the floor liked oranges? Or you have some kind of fungal infestation

 

[mark482]

Thanks, might try the chicken wire approach. Wouldn't I have to take up the floorboards to attach battens? Trying to avoid this since it's relatively easy to get under the floor (one area has already been cut to fit central heating).

A neighbour suggested the mysterious orange stuff might be rat poison? If so, either there are no rats or they don't like it much

 

[freddiemercurystwin]

You would have to lift the boards to fit battens so that the rigid insulation could sit on the battens, if you want to use rigid boards for increased insulation you could push your boards up into the gap (they should be a nice tight fit) knock (thin) nails into the bottom corner of the joists and tap them up a bit to stop the insulation dropping out (if you see what I mean)

 

[mark482]

Thanks, sitting on nails (the insulation not me ) sounds like an easier solution, working from below would be easier than taking up all the boards even if it does mean sliding around in dirt... Do you know what the solid boards are like for acoustic insulation - I think there's probably a path for sound via the party wall and void under the floor - could I put rockwool in then solid boards underneath, or is that bad in terms of ventilation?

 

[freddiemercurystwin]

The insulation should be tight up against the boards in anyway so no need to worry about ventilation. Presumably the void's vented anyway? http://www.insulation.kingspan.com/uk/pdf/k3.pdf page 3 Fig. 7.

 

[mark482]

Yes, void is vented, by a couple of air bricks at least. Survey on the house said the ventilation was inadequate, but the joists and boards all seem fine. Of course, that was the same survey which missed the asbestos roof tiles