Installing electric underfloor heating - Step by Step Guide

[andy8758]

Hi Bri. Never got around to reading this before. Excellent post. Love the idea of rsfa used to stop floating cable.

 

[dboden]

Bri, been reading your excellent post, got my first ufh in a couple of weeks. What did you use to put down the adhesive onto mat.. Back of trowel?
and did you mix it a bit more sloppy so its easier to spread?

 

[Ian]

Bri, been reading your excellent post, got my first ufh in a couple of weeks. What did you use to put down the adhesive onto mat.. Back of trowel?
and did you mix it a bit more sloppy so its easier to spread?

I use a an old grout float to apply the adhesive, safer for the cables. And I mix it a bit thicker than I would for tiling, it holds the cable down better and stops it popping up.

 

[dboden]

Brill thanks. I need a new grout float then!! So I have an old one. [emoji1]

 

[CJ]

I also keep a couple of cans of spray glue in my van........great for the odd bit they will not behave and lay flat.

 

[dboden]

Just a thought.. Wouldn't cable be easier to get flat?

 

[CJ]

Some makes are worse than others for edges/corners sticking up.......cable or mat. Make sure they are well stuck down before you self level. As soon as you start pouring the self level, it's too late then if they do want to float.

 

[Dan]

Just bumping some threads in the underfloor heating forum. You can now find and search for both electric underfloor heating and water underfloor heating threads. By the way, if you feel some of the threads you want to be seen at the top of the forum need to be bumped back, for the next month or so from now, feel free to do that. Although it's not usually something we allow, whilst we're going through this process of changing over forum software, we see the need for this to happen.

 

[DTCB]

Just thought I knock up a thread with step by step pictures of an electric underfloor heating installation.

Bare concrete floor (primed), 9 square metres. 100mm thick so was left 3 months to dry before I even thought about starting the job.
View attachment 26122

6mm insulation boards staggered and stuck to the substrate using a single part, flexible cement based adhesive. 1st picture, work in progress.
View attachment 26123

2nd picture, insulating complete. This particular brand says to butt joint the insulation boards so no need to leave expansion gaps between boards (check the manufacturers instructions).
View attachment 26124

(Check the mat is working and not damaged before this stage commences). Roll the mat out but do not stick it down until you are sure you have evenly covered the area and you are happy with the positioning. (This floor is 9m2 so the mat purchased is 8m2, remember the mat CAN NOT be shortened). To make turns in the mat cut the mesh but be VERY careful not to cut the wire, in the image below you can see where I have opened the mat up in places to get an even distribution. When you are happy with the positioning of the mat stick it down (this one has double sided tape on the underside). It is also worth mentioning at this point that when you roll the mat out make sure the power cable is closest to where the thermostat is going to be positioned.
View attachment 26125

In the same corner/part of the room you will now need to put the thermostat probe into the floor. This one is 200mm into the room (minimum for this manufacturer is 150mm. Check before fitting for different brands) and is placed in a conduit for protection. Make sure the probe DOES NOT go underneath any of the wires, this could cause the mat to malfunction or burn out and fail.
View attachment 26126

It is also worth mentioning that regular checks should be done throughout the fit to ensure the heating cable is still working and has not been damaged at any point. This mat came with a 'watchdog' that the power cable is connected to, and sounds an alarm if there is a break in the circuit from damage. Next stage cover the mat in flexible adhesive (same as the one used to fix the insulation boards), again be careful not to damage the mat, and stick down any bits of cable or mesh that are protruding. This stage could be skipped but I find it useful for sticking down any awkward bits of cable or mesh that won't lay flat.
View attachment 26127

Final stage (apart from electrical installation) is to put a flexible self levelling compound over the whole area.
View attachment 26128

When this has been given time to cure (48 hrs is ample) the electrical connection can be made and thermostat connected (by a qualified electrician) and the floor can be commissioned. This must be done before any tiling commences and the UFH must be switched off 24 hrs prior to the floor covering being laid.

Always read the instructions supplied with the product as there will be variation from each manufacturer.
I hope this is of use to somone and I hope I haven't left anything out! I'm sure someone will let me know if I have

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[DTCB]

Hi
What primer do you recommend and supplier? I was always advised to leave a gap of approx 20 mil around the edges - am I wrong? Has anyone any experience of tiling on an upstairs lime-ash floor and would you use any product on the surface prior to insulating and laying UFH?

Appreciate your thoughts DTCB

 

[DTCB]

Can someone point me in the direction of the polish tiler's work re-UFH pse?

 

[dean mckeown]

Great post. I am creating a wetroom and the only thing I am struggling with is as what point would you Tank the area. Do you tank the levelling solution or do you Tank the subfloor?