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JamesI, Developer
Category: Home Improvement
Satisfied Customers: 2980
Experience:  I have a portfolio of renovated houses, including DIY projects from installing bathrooms and new heating systems to rewiring.
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I'm considering installing an underfloor heating system

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Hi,I'm considering installing an underfloor heating system (electric) over an existing (old) solid floor in my kitchen.Reading around the subject, I'm getting wildly different recommendations on the insulation needed under the heating elements. Some sites say this should be 100mm minimum, and that this should be set under a screed (so insulation/screed/pads) whereas other sites suggest 6mm insulating boards directly under the pads.I'm concerned about both the additional floor height and the cost of digging up the existing solid floor.Can someone disentangle this for me?Many thanks, Chris.

Hi Chris, thank you for choosing Just Answer, my name is ***** ***** I will help with your query today.

It rather depends on the type of product you buy and what finished floor you want to end up with, are you wanting to have a tiled floor, laminate or carpet?

Do you have a preference of a particular type of element/heating product?

Customer: replied 9 months ago.
Hi James.Laminate floor (Amtico).
No view on heating element. The most reliable?Thanks, Chris

Right best practice tells us to ensure as much heat is directed upwards insulating boards should be placed below the underfloor heating, typically 6mm is used for most floors with the exception on concrete which is where your probably seeing reference to 10mm.

Depending on the heat output required, and the fact your using thin flooring you can probably get away without using any insulation under the heat mat and lay it directly on the wood floor, but to get the most out of it your better to use the 6mm insulation, otherwise may find the room takes a while to warm up.

Once down you then would normally scree the underfloor heating to give a level finish to fit your flooring, where fitting tiles you need not worry as the tile adhesive acts as the levelling compound, but in your case you would need to scree.

I hope this clarifies the situation with regard to flooring (6mm underlay - ideally) then scree finish. Let me know if you need anything further.

Customer: replied 9 months ago.
Hi James.That's helpful, but my question wasn't a typo. Some sources call for 100mm (not 10). Also, it's a solid (I.e.concrete) floor, not wood as you stated.Chris.

Sorry Chris, I thought I read your flood was chipboard.

Right if your using a concrete floor 10mm is all you require, where you install underfloor heating as part of fitting block and beam flooring its advisable to have additional insulation (though 100mm does sound excessive). In your case the screed is being used as a levelling compound and you dont have a great deal of insulation between heating element and final floor.

Give me a minute and I will see if I can find a tutorial video I sent to another customer last month.

Customer: replied 9 months ago.
Hi James.Here's the 100mm reference:'s under the section. 'installation in existing homes'Thanks, Chris

This is the video here I showed another customer about securing the insulation boards down, and Tops recommend using their standard boards on all floor types. Ive certainly never used anything more than 10mm insulation and never had any calls backs or concerns raised by customers.

Right the reference they are showing you is the floor construction itself, so if you were building a floor from scratch thats where they have got the 100mm from. In essence your existing flooring will have around 60mm above the sub floor anyway on older builds and nearer 75mm on new builds. The key thing to note is this is about making sure the heat radiates up and not down into the ground. The insulation boards you buy now are highly efficent and as I say I wouldnt have any concerns using a 10mm board on top of a concrete screed floor.

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Customer: replied 9 months ago.
Ok great. Thanks James, you've been most helpful.