Insulate (thermal/acoustic) kitchen floor under washing machine & tumble dryer: Can wooden board be replaced with rigid insulation?

[raidwi]

Our 1970s kitchen has a suspended floor, gets cold in winter and supports a washing machine and tumble dryer that I want to use at night on our cheap rate.

It has a very deep cavity with a lot of builder's rubble at the bottom, so access from underneath is a last resort.

Floor make-up is as follows from top to bottom:

Floor tiles
2-3mm foam layer
c. 15mm plywood sheets (each about 1m²)
Tongue & groove plywood very securely nailed to the joists (so much so I'm loathe to pull them up as I'll never get them back as securely and squeak-free).
Joists
Deep cavity

Which insulation materials could I replace one or more of these layers with? Ideally dealing with both the cold floor and dampen noise from the washing machine - e.g. can the plywood be replaced with rigid insulation of the same thickness that can support a washing machine?

Happy to provide any more relevant information.

 

[Mr Chibs]

You can 'float' a floor, like engineered wood on top of kingspan for example, but it might not be best way to go about it.

Any height you ad on top of the floorboards, means doors will need trimming and there will be a step-up from the proceeding room.

By the sounds of it, you have a suspend wooden floor, are you sure there is no trap door to access the sub floor area already?

 

[conny]

Do you just want to do under the washing machine or the whole floor?

 

[conny]

If you have access, (possibly in an adjoining room with less boards on top of the floorboards), you may find the builders rubble is not as bad as you think and can be shuffled around to create smaller mounds.
Kingspan/Celotex from underneath, secured in place with the odd batten across the underside, would probably be my way to go.
Small crawl spaces are not everybodys cup of tea though, so if you don't like working in small spaces it may a job for someone else.

 

[raidwi]

You can 'float' a floor, like engineered wood on top of kingspan for example, but it might not be best way to go about it.

Any height you ad on top of the floorboards, means doors will need trimming and there will be a step-up from the proceeding room.

By the sounds of it, you have a suspend wooden floor, are you sure there is no trap door to access the sub floor area already?

Sadly no trapdoor

 

[raidwi]

Do you just want to do under the washing machine or the whole floor?

Just the area where the washing machine is for now. Had a leak so some of the tiles and plywood sheets are already up

 

[conny]

In that case, carefully cut through the exposed floorboards where they meet the joists, (number them in sequence so they go back in the same place). After removing you can reach down and put a couple of battens across the underside and then add a block of insulation. You will also need to fix battens to the side of the joists for the floorboards to rest on and be screwed down to.
Though to be honest, I can't see what doing this small area is going to achieve.