Insulating bathroom floor unsure

[Palmtree]

Hi all, grateful of your views.
I’ve a Victorian house with downstairs bathroom with a concrete floor - very cold!
Want to insulate with rigid celotex or similar over a DPM.
We have a Victorian style bath ( lightweight acrylic not cast iron) on 4 legs, each leg load is on about a sq inch of floor.

My question is, will floating a p5 chipboard floor straight over the celotex be up to the job ( so a proper floating floor) or given the weight on such a small area, should I batten out the floor at something like 300-400 mm centres ( which will give some cold bridging) and celotex in between.
Floor will be 10mm tile on 6mm backer board on 22mm thick chipboard. Just don’t want the bath to sink!

(Bath waste will need to go straight down into the floor, so planning on carving a small trench into the celotex for pipe work with 25mm clearance around pipes to account for any slight movement in floating floor).
Many thanks, Jason

 

[robinbanks]

I'd use celotex with no battens and a small spreader plate under each leg depending on how pointy the underside of the foot (to protect the tile from a being point loaded and cracking)

Also, if you're dot dabbing tiles elsewhere in the room, don't dot n dab the tiles around where the bath legs will be, strive for an even bed of adhesive (on a consistent floor like you're creating I'd be using a full adhesive bed all over, 10mm notch trowel)

 

[Palmtree]

Many thanks for the reply. Really helpful tips, cheers.

 

[^woody^]

You don't say how thick the insulation will be, or what you hope to achieve.

If you want to make the room warmer, then insulation on the floor may not be much of an improvement for the effort and cost.

If you just want to remove a cold floor feeling, then the chip board will do that.

IIRC, Styrofoam is denser than Celotex and is often used in insulating floating floors.