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Electrical Under Tile Heating

Postby shipyardspark » Sun Nov 08, 2009 3:59 pm

Hi Folks, considering installing electrical under tile heating in a shower room. This will be connected to an RCD cct in the CU via a switched spur and the thermostat, so am confident electrically all is covered. My question, however, is to do with installation of the heating cable or mat. This will be installed on a wooden floor. The floor is 22mm floor board with 100mm Celtex insulation between the joists. Do I have to install insulation boards on to the existing floor before laying the mat or cable? I am concerned that the final floor height will be significantly higher (30/40mm) than the existing floor and am hoping that the existing insulation will be sufficient. Anyone have any thoughts.
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Simply Build It

Postby ericmark » Sun Nov 08, 2009 10:35 pm

We used in Mothers wet room to dry floor as she only has one leg. The floor was about 1/2" below finished when we laid cable the earth braided type so it was not necessary to lay an earthed mat above it. And it is the earthing requirements when used in wet rooms which guided our selection.

However because the tiles were sculptured again to increase grip they retain too much water to dry as expected. Although a drip will soon evaporate once the show has been used the tiles take too long to re-heat up after being cooled by shower water.

It was also a surprise as to heat output. Any hotter it would burn ones feet but does not really warm room and without the heated towel rail it would be rather cold.

It has been down 3 years and thermostat has already been replaced and the sensor in a pocket as instructions failed and is jammed in pocket so can't be renewed.

In all rather a disappointment and I would not fit it again as least not electric.

We bought the unit from Tops Tiles and they did give good advice but I was really surprised how quickly and completely the shower water cooled the tiles they do take half an hour to warm up. And my mother now does not switch it on. Although part because of cost.
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Postby speedygonzarlis » Thu Nov 12, 2009 8:01 pm

As eric says electric under floor heating will not heat the room as a primary source, i fit this regularly, in such a small space it is just a luxury item to take the chill out of the tiles, so your feet feel nice, you can either lay it on ply, minimum 12mm screwed every 4inches or on the insulation boards, the tiles warm a little quicker on the insulation boards, if you use insulation boards you must use large 1inch washer on your screws to stop them pulling through the board, and put screws in at 150mm centres, prime the boards or ply with a synthetic primer, lay the matting then screed the hole floor area with a latex self levelling compound, you must have no cable showing before tiling!! and check continuity of matt and thermocouple before and after installation to ensure no damage has been coursed.
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