new bathroom, floor,

[van]

hi, just replaced old t+g floor with 18m chipboard. We would now like to put underfloor heating in before tiling. Is the chipboard o k or should we replace it with something else. We are good DIYers and as we are completly refubishing our bathroom we want it to be right.

 

[Gazzer]

No to chipboard. Replace with 18mm WBP ply.
While you have the floor up why not add strength to the floor with extra noggins.
Consider the use of a insulation board before laying UFH mats and then tile using SPF adhesive and a suitable flexible grout.

 

[van]

we are going to put insulation under actual floor so is there still any need for insulation boards?

 

[grumpygrouter]

we are going to put insulation under actual floor so is there still any need for insulation boards?

It helps to reflect the heat up into the tiles, what it costs you for the insulation boards and extra fixing material, you will more than make up for in cheaper running costs within a few months. But yes insulate underneath as well.

 

[Gazzer]

we are going to put insulation under actual floor so is there still any need for insulation boards?

Think of it this way, if you dont use insulation boards you will be heating the wood up as well as the tiles. Wood will move with changes of heat. By using Insulation mats you will be keeping the heat above the floor and up into the tiles.
As Russ says, the cost of the insulation will pay for itself in the long term and you will get quicker warm up times.