Wedi board

[nsko]

Hi Guys i am looking to lay 6mm wedi board over chipboard prior to installing underfloor heating 3.44m2 room size will i get away without using wedi fixing screws over that area i was going to leave a 4-5mm gap around edge of room, but can i butt joints of boards together tight.

[diamondtiling]

You can butt joint them and your gap around the perimeter is fine, I would use screws as well just for peace of mind. Dont forget to bond the floor

[nsko]

can i get away with normal screws

[diamondtiling]

If you are trying to save on cost then you are trying to save on the fundamental part of the installation, i.e. the floor itself.

Make sure the chipboard is screwed down and solid with no deflection at all.
Apply acrylic bond to the chipboard, two coats.
Fit your thermal boards using flexible adhesive leaving your gap around the perimeter.
Use the appropriate screws and special washers as you go, they are there to do a job.

[poynton phil]

I'v always used plywood, rather than backerboard on floors, but have decided to change my ways. I was just wondering if anyone knows of a suppler of backer board screws, as i cant seem to find one, or could i use a stainless steel, or brass screw instead. Also do i screw the heads down level with the board, or leave them slightly raised, as i was told by a mate to do. Thanks for any advice.

[Dave]

Stainless steel will do and screw them down tight just level with the surafce...leave a 2mm gap between boards and use an alkali resistant scrim tape over the joints to strengthen and skim in with adhesive.

[diamondtiling]

stainless steel will do the job I agree but at more cost than the readily available screws that are supplied for the job

[poynton phil]

could you tell me who stocks the screws for the backer board please diamond, as i cant find a shop that stocks them.

[andy63]

HI Phil

Im new here but I have used wedi a fair bit on my walls; you only need to use the wedi washers with any standard drywall screws; screwfix have a range of sizes to suit. Rule of thumb is screw length should be 2.5 x board thickness.

andy