hi, i am working on a job and the guy wants to lay underfloor heating on to marine ply is this ok. it has already gone wrong once. cold in places and to hot in others. ????????

Jason, generally up to 100W cable is ok onto plywood, the probable reason for hot and cold spots could be that a solid bed method of adhesive fixing has not been acheived. A good recommendation is to avoid plywood and opt for minimun of 10mm insulation board such as Marmox or Wedi, this will maximise the systems efficiency and minimise running costs......I hope this helps

Gaz

Marmox Insulation Board

I'm with Gaz on this - use an insulation board if height permits as not only will it make the system more efficient to run ( no heat loss and faster warm up times) but you'll also eliminate that contact between wood, mats' latex / addy which is best avoided where possible (IMO).

Gaz, on the subject of UFH, have you any opinions on the use of UFH mats (not embedded in a screed but fixed under tile as above) being used as a sole source of heating in a well insulated room. I've been following some manufacturers claims that this can be done by insulating floors and using higher wattage mats but I've also been told that this cannot be achieved (sole heating with mats fixed in the conventional way) and any manufacturer claiming this is incorrect......

This post has been edited by aostiling: Aug 10 2009, 07:30 PM

Andrew, These claims by UFH companies are true in well insulated rooms. If sitting on insulation boards driving the heat up and with solid bed fixing it works lovely. Regards flooding the cable, this does not reduce the efficiency of the system ...except slightly on start up, but the advantage is A. Less chance of damage when fixing, & replacing impact damaged tiles reduced risk of cable damages. hope this helps.....Gaz

I always recommend insulation board .....
Will work without, but....
Will cost more to run, BUT WITHOUT it will only serve as floor warming !
When you use insulation board it is then classed as under floor heating.
Best practice is also to self level over the cable prior to tiling with a BAL flexible self levelling compound.....
this will
a. protect the cable during tile installation
b. enable you to get a good solid bed of adhesive, thus avoiding air pockets that can create hot spots
c. make it more possible to remove tiles in the future without damaging the cable, should one be damaged.

very helpful thanks

We Have 2 dates for Southampton Centre for early next year for Devi underfloor heating systems training. The dates are 20th January, 3rd February. If any of you are local or willing to travel the course is free and is run in association with Bal.

You can e-mail me on vruffini@building-adhesives.com or tel 07968 959632

All these questions can be answered even if you use a different system.

Does anyone know where abouts in north of england can you get Marmox ? 12no 8x4x20mm delivered on site.

Try marmox4u.co.uk. Will deliver anywhere next day if order in by 1430