Hi Guys,

Ive been tiling 2 years and never done an underfloor heating job, it has been requested by a customer, the floor in chipboard can you please suggest the correct fixing methods?

Cheers

Paul

Do you mean the electric matt..

good luck its a brave tiler that tiles over chipboard and ufh ,you may be better off getting a technical spec from an adhesive manufacturer who will stand by the job if it should fail

Originally Posted by whitebeam

Do you mean the electric matt..

Yes mate

Originally Posted by garythetiler

good luck its a brave tiler that tiles over chipboard and ufh ,you may be better off getting a technical spec from an adhesive manufacturer who will stand by the job if it should fail

I was going to ply first

What room is it, small bathroom etc

Originally Posted by whitebeam

What room is it, small bathroom etc

Small wc and hall

Originally Posted by shogun rua

I was going to ply first

If the floor is solid, then insulation board would be a better option.

Originally Posted by grumpygrouter

If the floor is solid, then insulation board would be a better option.

do you need to lay slc on top of the board

As grumpy, electric matt on the boards then slc, what tiles are you fixing

Originally Posted by whitebeam

As grumpy, electric matt on the boards then slc, what tiles are you fixing

ceramics i think mate

Just thought it might be natural stone, ceramics should ok

Please also ask yourself what you want from your underfloor heating system.

On top of the already laid screed or insulation boards as Construction Boards etc, you can use Elektra MD160/MD200 underfloor heating Mat or same output in Elektra DM10 loose cable. 160w/m2 or 200w/m2 output underfloor system will be a heating system. As the guys above for your floor finish. ( always powder flexible )

On top of the already load bearing timber base, you can only use Elektra MD100 underfloor heating Mat or same output in Elektra DM10 loose cable. This Elektra underfloor heating system may or may not be a total heating solution, depending upon the heat loss & how well insulated the dwelling is.

When using a 6mm insulation board with u/f heating the overall extra thickness needed is 8mm: 6mm board with 2mm powder flexible tile adhesive under to fix the boards.

Make sure you get that floor totally movement free, screw it to death and make sure that there is no deflection. then overboard with a backer board like hardie or no more ply, this needs to be screwed and glued down. Then you can install the UHF mat over this. The main thing is to get the right mat, read the installation instructions and follow them to the letter. I imagine that 99.9% of jobs that go wrong with under floor heating are down to people not following the instructions properly. Then I would SLC over the top of the wires (make sure that the SLC is suitable) and then tile.


It really is a piece of cake as long as you do each stage in accordance with the manufactures guidelines.

Originally Posted by Rich

Make sure you get that floor totally movement free, screw it to death and make sure that there is no deflection. then overboard with a backer board like hardie or no more ply, this needs to be screwed and glued down. Then you can install the UHF mat over this. The main thing is to get the right mat, read the installation instructions and follow them to the letter. I imagine that 99.9% of jobs that go wrong with under floor heating are down to people not following the instructions properly. Then I would SLC over the top of the wires (make sure that the SLC is suitable) and then tile.


It really is a piece of cake as long as you do each stage in accordance with the manufactures guidelines.

Could you avoid slc by buttering the tiles or is this essential

No it is not essential, some people dont SLC and tile directly over the wires to save time but in my opinion it is much better to SLC as it protects the wires while you are working, it helps to spread the heat over the floor and most importantly it is far easier to get 100% coverage of adhesive under the tiles.

If you choose to tile straight over the wires make sure that the adhesive you are going to use is suitable. Building up over the wires and then tiling might well be over the max depth of the adhesive.

Originally Posted by shogun rua

Could you avoid slc by buttering the tiles or is this essential

It is much slower/harder to do it this way. Even if you trowel the floor with the bare wires it takes you much longer because of the care you need to take to not damage the cables. SLC makes it a much more pleasant tiling experience with UFH, over and above the other benefits already mentioned. It would probably work out cheaper too as you will use much more adhesive to fill up the void between the cables and adhesive is generally more expensive than SLC.

Hi Again,

Im going to lay installation boards i was told today to put down with addy then screw down but to use washers is this what you would do?

Cheers

Paul

Yep, that's fine.

Hi,

Heres my plan lol

1. check the chipboard for deflection fix if needed.
2. lay insulation boards with rapid set and screw down with 25mm screws with washers( do i dot and dab or back butter?)
4. prime with the expensive primer.
4. lay electric mat to the installation instructions to the word.
4. lay slc (fibre based)
5. tile (do i need to use a plastic trowel?)

what do you guy think?

have you checked to make sure its not a floating floor?

Hi Andy,

How do i check that mate?

Cheers

Paul

a floating floor is just chip board over insulation with no fixings, try lifting some of the flooring and look for fixings where its screwed to joists, if there are none then theres a good chance its a floater in which case i wouldn't touch it with a barge pole.

great tip Andy cheers, so dont tile on floating floors then to move movement

imo there to unstable, with to much deflection.

what do you think of the list did i miss anything?

Your list seems good as long as you follow each stage to the installation instructions all the way through the project. It is vital to get a solid bed of adhesive under the cement boards and the tiles, you shouldnt ever "dot and dab" anything apart from plasterboard on walls (that I can think of). This shouldnt be hard with your floor, trowel the adhesive on the floor and press the boards down into it firmly and give them a bit of a twist making sure that the corners and edges are well and truly bedded down into the adhesive, then the screws do a good job of pulling the boards down into the adhesive bed.

thanks 12mm trowel

Not for the cement boards, I use a 6mm on most floors. Only use a bigger trowel if I dont get a good coverage with that. A half moon trowel for laying the tiles and you will want to back butter the back of the tiles with the flat edge of the trowel before laying them into the adhesive bed as well, this should give you a better chance of getting 100% coverage

do you always back butter your floor tiles aswell as lying addy on the floor?