Questions about Underfloor heating

[Dan Ryan]

I've had two quotes for tiling a kitchen and hallway. The kitchen is to have underfloor heating, just enough heat to warm the tiles as have radiator in the kitchen already. One tiler said single wire would be fine for my circumstances, the other said the matt system would be best. The area is approx 2m sq.Which would you install and what are the snags with either of them?Also do I need to have a switched spur connected to the underfloor heating system. The tiler is proposing the single wire system has said 150W is enough, could I get away with 100W system as this is just to warm the tiles? Tile on top are to be 0.9cm thick porcelain. The property is a new build, do I need insulation boards under the wire, can you get a liquid screed that works as insulation in place of insulation board? Tiler has also mentioned that tile insulation boards I could probably get away with, as won't have much heat loss downwards from the wire and also that it means I wont need to worry about insulation boards costs and getting all the hallway to match the kitchen level.

 

[GoneGuy]

With ufh you need insulation boards otherwise you will loose a high % of heat through the substrate.
Difference with mat and loose lay is that if you have a lot of obstacles it’s easier to lay loose wire around these.

 

[Boggs]

If it’s Warmup you are thinking of using I would recommend using the 4ie stat.
You can set the temperature of the floor as opposed to the air temp.
This way you could set it to 16 or so degrees, enough to take the chill out of the tiles but not so it’s trying to heat the room.

As said above to get the best from it you will need to use insulated backer board and you will need a switched fused spur.

 

[Dan Ryan]

Thanks for your responses. I have a feeling I'll have to go the insulation route, could be that doors will need to be planed etc! How about fast heat - thermal floor primer, is it any good at providing insulation to prevent heat loss downwards from the wire?Am I correct in thinking the layers would be primer, adhesive, insulation board (6mm), wire, adhesive and then tile?If I went for 6mm insulation board could you let me know if the above levels make up is correct and what the typical depths would be for them?I'm trying to work out how high the finished floor will likley be. Also is the wire usually less deep than the pre-made matt system?

 

[Perfect Tiling]

If its a timber floor you should use 10mm insulation boards...6mm for a cement floor....staggered layout...glued and screwed with washers. Make sure its the correct boards that have the fibre rienforcement on both sides and mesh tape the joints with an alkali resistant tape.....I had a customer who got boards off the internet cheaply and they were just insulation.....no fibre so no use.
The difference in thickness between mat or loose wire is hardly noticeable.

 

[Dan Ryan]

Perfect tiling when you say glued and screwed is that just for a timber floor?For the cememt floor I thought it was adhesive that went down?Do you think 100W is enough to just warm the tiles up rather than 150W?I already have heating that is sufficient in the room where the underfloor heating will go.

 

[J Sid]

for the small extra cost why not go for 150W ?

 

[Dumbo]

for the small extra cost why not go for 150W ?

Agreed it won't use anymore electric it will just get to heat quicker as the spacing is closer .
Like 3kw kettle compared to a 1.5kw kettle . Yes it uses more juice but for only half the time

 

[CJ]

TTACH]

 

[WetSaw]

@Uheat - Jake ....

 

[Flintstone]

I nearly always just go for 200w because, well why not ?

 

[Uheat - Jake]

Thanks @pdc

Your best option in such a small area is to take a 160w/m2 or 200w/m2 as the cost difference between mats at the small sizes is so marginal its cost effective to future proof incase you want to remove the rad in the future.
I'd also recommend either a 6 or 10mm Backerboard down first as well to help reflect the heat and stop any heat escaping downwards.

And finally, give us a shout for a quotation. Forum members receive extra discount.

 

[Dan Ryan]

Thanks for all your replies on the heat mat, you're right it just gets up to heat quicker. How about the fixing - glued and screwed is that just for timber or for cement as well?Reason being if its cement I might be able to save depth with less adhesive below insulation.

 

[Waluigi]

Glued only.

 

[Dan Ryan]

Even more confused now. So the insulation boards should be just glued down and not screwed?I thought originally they were meant to be laid on a bed of adhesive.What I am a bit concerned about is that say the finished floor after its all installed is at 30mm I then have to match this with new carpet and underlay in a adjoining room.If I reduced the total height of the installation without reducing the quality of the work it's be great.

 

[Dumbo]

Glued means use adhesive . As regards height it is what it is . It's function over form . After a while you won't notice the height difference and wonder what the fuss was about especially if you fix a purpose made threshold out of timber to accommodate the difference . But if your ufh doesnt work properly it will always not work properly and you won't get over that .

 

[Andy Rhodes]

Dan I would bedded the insulation boards on a 6-8mm flexible adhesive bed mechanically fix the boards down then with the fitting that go with the boards which you can get from the company that supplied the board the UFH matting normal has a sticky side which isn't all the great so I would use a stable gun to hold down the matting but nowhere near the heating wire as you only what to hold it in place until you've screed over the matting with a levelling screed by doing this you with optimise the full function of your UFH , as it will distribute the heat equally all over the floor making it most cost efficient to heat

 

[Uheat - Jake]

If you're going onto a screed you can use the XPS Insualtion boards.

We recommend these are stuck down with a 2mm bed of adhesive. These don't need to be mechanically fixed as there's no bounce on a solid concrete floor. Mechanically fixing is only really used with Timber subfloor.

 

[Dan Ryan]

Aha yeh you meant tile adhesive , I'm not up with the terminology!

What total build height do you think I'm looking at?

I'm also thinking of using carpet shims and thick underlay when the carpet gets replaced to make up some of the height difference to the finished tiled floor.Last thing I want is to have a proud threshold that we keep tripping over.

 

[Uheat - Jake]

The usual build up is around 18-20mm before tiles. You normally have the following,
2mm adhesive bed for insulation
6mm insulation
4mm heating mat
6-8 flexible slc

 

[Dan Ryan]

Thanks I've heard 25-30mm. That 5mm will make quite a difference, with the transition to the future carpeted room.10mm underlay and 12mm carpet. Ive then got 8mm to make up with carpet shims. Probably not a great finish as you'll see the slope and trip on it. Other option would be to screed the carpeted room's floor, but that will run into a small fortune I don't have.

 

[Andy Rhodes]

Is the carpet been laid on a solid floor or on floorboards

 

[Andy Rhodes]

by that i mean whats you base

 

[Dan Ryan]

by that i mean whats you base

On solid floor. Concrete screed.

 

[Andy Rhodes]

you could possibly build up the carpeted area on the green minerals boards the use for lamnate flooring lay your underlay on that then your carpet if need be double layer it that between 7-9 mm thick or screw down 12mm marine plywood down to raise the floor up that would be cheaper the levelling screed as that come in 8 x 4 sheets