Morning all.

I have a job coming up where the client has asked if i would install UFH on top of quarry tiles that are basically bedded on dirt.

They dont want the expense of having to rip it all up and have a new concrete floor put down.

They are then having it tiled over.

Can anyone see any issue with the mat going on the existing quarry tiles?

Cheers!

Hi Jason, its not a very good base to tile on is it? I would imagine the insulation value is zero so the heat requirement from the mat will be high in order to maintain a sufficient temperature. How solid is the existing floor?

would they go for insulation boards over existing?

If the old quarries are solid - I mean proper solid and not hollow or loose when tapping with a small hammer, then you might consider

1 Slurry primer with SBR / OPC mix
2 Overboard with suitable insulation boards - suggest 10mm / 15mm min on thick bed 20mm bead / flex addy
3 Lay UFH
4 SLC - Latex or similar high flex to cover cables completely
5 Tile

What height increase can you accept ?

Proper job would be to take the floor out and insulate a new screed with a DPC but it could work 1/5 above but warning to the wise - only if the old quarries are really solid .

best bet rip it up first

Hi J..

Deffo needs some insulation mate first..

Cheers chaps.

I have yet to visit the site (next wed eve), as this is only what i have been told by the kitchen company.

The tiler will also be on site, and i think he may say the same......rip it up and start again.


Ta again.

Hi Jason

Just noticed your logo - That could only happen in the States - Am I right ? You electrical types - what are u like

Thanks Rich

So,

Quick update,

Went to look at the job and its rectangular quarry tiles bedded on solid concrete and not dirt.

Client is happy to have 10mm insulation under the Heat Mat UFH.

Just priced it at an online retailer and it comes out at nearly £1000!!!!!!!!!

Eek.

Anyone know anywhere that may be a little cheaperer?

Ta.

Phone them up and tell them you are a tilers arms member and a mod.. that will get the price down.

Originally Posted by Jason S

Thanks Rich

So,

Quick update,

Went to look at the job and its rectangular quarry tiles bedded on solid concrete and not dirt.

Client is happy to have 10mm insulation under the Heat Mat UFH.

Just priced it at an online retailer and it comes out at nearly £1000!!!!!!!!!

Eek.

Anyone know anywhere that may be a little cheaperer?

Ta.

Have you tried Uheat J?

Underfloor Heating | Electric | Floor Insulation | Uheat

Originally Posted by Dave

Phone them up and tell them you are a tilers arms member and a mod.. that will get the price down.

Thanks Dave, but im not sure it was a sponsor of the forum...

Oli, no i havent. Ill have a quick look.

Ah!! I thought it was Uheat..LOL.. deffo try them..

Just had a look and it looks like their own brand.

Customer is sold on Heat Mat

Hello Jason

I would shop around a bit and try Uheat too - However warning call - Value for money is one thing, but cheaper is not always cheaper in the end. Little details are missed of by ' third world ' made UFH systems - ie no black 20mm ducting to run the probe in to enable probe to be replaced in the future. - Controllers do vary

Good luck with the job

There will be no DPM under the existing tiles. That puts your new tiles at risk especially if the new tile face is heated. Also if there is no insulation the heat mat will simply be trying to heat up the world cos there will also be no thermal insulation under the quarries. Best thing would of course be rip em up and do it properly but I would say minimum would be 1200g DPM over the existing tiles then some insulation board suitable for the UFH mat, then SLC followed by tiles. To get the highest thermal conductivity you might wat to consider SLC based on Gypsum and then adhesive based on the same.

Sound advice - as always from Ajax - You might be alright without DPM as the floor might have a DPM and if not I think if you used cementous boards as opposed to std insulation boards and taped and sealed the joints, then this is waterproof too. You will have to check the K value of the two board types with the manufacturers and compare the test results for the same thickness.

The only aspect my advice might differ from Ajax is - If you used Gypsum SLC with a higher insulation value, this might work against you, as the SLC is used to cover the cables and what you should be aiming for is max insulation under the cables and minimum around / on top of them to transfer max energy to the tile surface, hence I would go for Cement based high flex / latex.