Underfloor heating over existing floor

[deema]

I’m considering having underfloor heating added to my upstairs. The floor is wooden, and I’d dismissed it as I thought it involved taking the floor up adding insulation into the void, adding metal reflectors laying pipe and the floor back down. However, it’s been suggested that pipes can by layer on top of the floor and a thin screed spoiled, around 16mm total thickness added to the floor height. Does anyone know anything about this type of system, any good? Things to watch out for reasons not to do it? Best system?
Thanks

 

[Myfordman]

I would imagine the screed would crack in no time with flexing in the original floor plus heating and cooling cycles.

 

[Adam W.]

I've seen it laid on chipboard with aluminium tray thingies underneath, not sure what the top finish was, maybe engineered wood flooring which I have used sucessfuly over UFH in screed before.

 

[Pedronicus]

Loprolite

 

[Garden Shed Projects]

Loprolite

Looks like a good idea. I am about to start a renovation at home and will definitely explore this option.

 

[Spectric]

You are not saying if you are looking at a wet system or electric.

With a wet system the tray system is really new build but there are other options for retrofit. Take a look at this system for suspended floors

https://profixpanel.co.uk/low-profile-screed-system

 

[deema]

Apologise, wet system over wooden joist floor.

 

[Geoff_S]

We put a wet system into our kitchen (rip out & rebuild) with a new joisted floor. Insulated blocks were set between the joists in which the pipes were laid. Chipboard T&G flooring was laid over this, followed by ply, then levelling compound then Karndean flooring.

So, exactly what you plan not to do. However, what I would say is that it's OK for providing background heat. In our kitchen which is a new build'ish, it's properly insulated and we of course get a lot of extra heat from the oven, hob and even the boiler. I'm sure that had we done this anywhere else in the house, we would have been a bit chill.

I think that @Myfordman sums up a major concern with your idea though.

 

[Jameshow]

Surely it's not beyond the scope of a CNC shop to cut a maze into 18mm plywood into which the pipe is laid. Then laminate / tiles are placed over the top?

If the pipes go tangential to the joists it shouldn't be a problem.

2 8x4 sheets would warm the majority a typical sized room.

 

[Geoff_S]

How big is the floor area being covered ?

How many doors are going to need trimming?

Is there a loo that’s going to need heating? Same question on bathroom. Is there enough floor area in these rooms?

Where’s the manifold going to go?

 

[Spectric]

I'm sure that had we done this anywhere else in the house, we would have been a bit chill.

I would put that down to a design issue because a properly designed and installed UFH system provides more than enough heat but a key part is the pipe spacing and loop lengths, plus the loop layout. It is more difficult if you are trying to keep the build height low but you should get about 70 watts per sq metre and UFH is direct from the floor which is thought of as better than just a radiator. Modern screeds don't mind the heating / cooling but will not like any excessive flex in the floor but will be ok with some, this is a good fibre reinforced compound

https://www.tilemasteradhesives.co.uk/floor-levelling/levelflex-self-levelling-floor-compound

 

[ian33a]

We have underfloor heating upstairs (as well as downstairs) but was laid under floorboards by the previous owner.

Most of the upstairs is carpeted, not ideal for UFH, but it works. We have a couple of ensuites where there are tiles. We also had a main bathroom with tiles. All of the tiles have either moved slightly and cracked the grout or the tile has actually cracked (as was the case in the main bathroom).

The very experienced and thorough fitter who refitted our bathroom said that, almost without exception, tiles, grout and screed, layed on top of floor boards unless the floor is heavily stabilised with plywood, will always crack. Even with a stable plywood base, it may still do so if there is movement in the joists.

Not that we considered tiles, but in our bathroom, we went for a click flooring system layed on a membrane (if I recall correctly).

A 16mm increase in stack, while maintaining ceiling height, sounds good in principle, but I would seriously consider a suitable laminate flooring and avoid anything ceramic - or go with a low tog carpet.

 

[Bingy man]

The only low profile ufh I’ve ever fitted was the electric mat type laid on the floor then simply tiled over but the electricity cost these days makes it too expensive. As per other posts it’s only a background heat that still requires radiators to maintain 20-21deg . There are several options now available for ufh but my limited research makes solid floors the most expensive and invasive to install. If the total height of the ufh system is for arguments sake 75mm then add 100mm for installation 75-100mm for concrete/ screed +the finish flooring height approx 15-20mm-a total in excess of 300mm that has to be removed from the existing floor height before you even start . My current customer has a large detached house that is being renovated and he is very keen on ufh as apparently it increases the property value and also gives him an additional selling point . The systems for ufh in joisted ceilings/ floors are purpose designed and there are various companies that will provide all the various components to install ufl in ceiling voids . I should add all these systems are designed for wet central heating so the additional heat input of the ufh will have to be added to the radiator and hot water req of the system and the boiler sized accordingly .I’ll see if I still have the links I sent my customer . Obviously the level of insulation within the property will play a major roll in how warm a room can be maintained with just ufh on its own or adding/keeping radiators as well. My customers property is detached, no cavity’s , 3 mtr ceiling height and 75%of the ground floor are suspended .

 

[XTiffy]

I built two cottages and used the Nuheat Lopro on top of chipboard floor, 12 years ago, this was for upstairs. The ground floor also had u/floor heating with Knauf flooring and then Oak laminated flooring. From memory the pipes were laid in grooved polystyrene sheets and then thin plywood over that. In our case fitted carpet upstairs. The whole u/floor heating was zoned. It all worked well with no problems. The two cottages both ran off of their own air source heatpumps.

 

[XTiffy]

I forgot to say the increase in height was only around 20-25mm, plus carpet!

 

[Bingy man]

How to Prepare an Old Property for Underfloor Heating



This guy rabbits on a fair bit but gets there in the end . A useful insight into ufh for anyone who may be interested or considering it .

 

[Bingy man]

ambienteufh.co.uk
https://www.ambienteufh.co.ukSuspended Floor UFH - Wet Underfloor Heating

https://www.theunderfloorheatingstore.com/

Continal Underfloor Heating
Continal Underfloor Heating | UK's widest range of UFH systems › systems
Suspended floor UFH systems
If you are looking for a suspended underfloor heating solution then look no further than us. Joisted floor UFH, where a floor deck is supported by timber or ...


https://www.theunderfloorheatingstore.com/knowledge-hub/guides/between-joists-or-suspended-floors

 

[XTiffy]

I just found this photo, which shows downstairs u/floor heating but the upstairs looked the same.

 

[Jameshow]

We have underfloor heating upstairs (as well as downstairs) but was laid under floorboards by the previous owner.

Most of the upstairs is carpeted, not ideal for UFH, but it works. We have a couple of ensuites where there are tiles. We also had a main bathroom with tiles. All of the tiles have either moved slightly and cracked the grout or the tile has actually cracked (as was the case in the main bathroom).

The very experienced and thorough fitter who refitted our bathroom said that, almost without exception, tiles, grout and screed, layed on top of floor boards unless the floor is heavily stabilised with plywood, will always crack. Even with a stable plywood base, it may still do so if there is movement in the joists.

Not that we considered tiles, but in our bathroom, we went for a click flooring system layed on a membrane (if I recall correctly).

A 16mm increase in stack, while maintaining ceiling height, sounds good in principle, but I would seriously consider a suitable laminate flooring and avoid anything ceramic - or go with a low tog carpet.

Would a epoxy grout be better as it's stronger and more flexible, indeed as it heats up it increases in flex?!

 

[pe2dave]

Wondering if you have any central heating / other plumbing under the floor you are considering?Assume you'll never need to get to those pipes?
Mmm.