Wet underfloor heating

[MoonShadow11]

We’re just going through a property purchase and after a great response to my kitchen size dilemma thread, I’d like to ask about ufh.

I’ve looked into this and I think wet ufh will be a better option for us and also cheaper than electric. We would only require this in the kitchen and dining room. I have had a search on here and it seems that there’s no need for any digging and the floor level won’t be raised enough to be noticeable. Is this correct? We’d don’t want to go down this route if it is too complex.

Would appreciate some advice on this.

For a shitty incompetent lay on top UFH system with no additional insulation underneath to avoid wasting heat, you're looking at minimum 6cm depth on top of your existing floor. A proper system would include 10+cm of underlay.

When you say "a search on here", do you mean on Mumsnet, that well known source of plumbing info? Best ask some real installers instead.

What is the current floor construction Moonshadow?

We've just retrofitted wet UFH in a section of our downstairs and considered a variety of options in installing it but in the end settled for replacing the traditional floating wooden floor with a proper concrete subfloor and the cost was not very different from lifting the existing floorboards, insulating and laying UFH etc. ANd we have no difference in the floor levels now between the old floating floor section and the UFH section. Important to remember that if you consider such a fix, the floating floor section must be ventilated to prevent rot.

If you have a concrete subfloor channels can be cut into it for the pipes, but there wouldn't be any insulation below it, and you would still end up with different levels as you need to consider the screed top and floor coverings over the top of the pipes.

As Spoon suggests, why don't you get a couple of builders/installers in to advice and quote?

Don't use electric. It will bankrupt you

Proper UFH required 50cm depth. We have and is wonderful. The plumber wouldn't recommend retrofit.

EastCoastDamsel it is concrete. Sounds like it’s a lot more complex than I thought so will speak to an installer about it.

Definitely won’t be having electric ufh MarieG10. It will have to be retrofit though so hoping we can find an installer who can advise on this.

I just don’t see how retro fit wet can possibly work efficiently. We have it in most areas of our ground floor but the floors were dug up. That also means they are level with all existing areas. You also have to consider your pipes that will feed the system. How will they be inserted.

Did you have it on your existing floors BubblesBuddy?

It isn't just the sub optimal nature of the retro fit, the key is the significant insulation required in the floor. We had 10 cm depth minimum if I recall correctly.

Oh my post above ...it is 50mm depth required not 50 cm

Foolishly I didn’t even think about the insulation required

Will have to get it looked at and see what can be done.

@MoonShadow11 j less you can dig up and relay the floor, I would stick to conventional radiators. UFH is delightful, we had a large kitchen lounge and diner built and one of the luxuries we have is the UFH. Also great not having radiators on the wall. BUT...the plumber said it must be done properly. Ie insulation fully correct, and more the better and proper continuous runs of pipe with no joins and then screened. Also note that the screed can take months to dry, although the UFH can speed it up once switched in gently.

Honestly, I wouldn't do it unless you can do a proper job on it

Don't do it if you can't insulate - you'll be heating the ground! Of course, insulating under the floor is a good idea anyway, (albeit a big old job) even if you stick to rads.

Are you insulating anywhere else? - when the builders are already in - esepcially if you aren't ? - is definitely the time to do this, you have far more options!

Thank you MarieG10 and candycane222. Have taken your comments.

We will be replacing the flooring throughout the house and getting a new kitchen and utility fitted but don’t need insulation anywhere else.

We had the concrete floor taken out, insulation fitted and then retrofit underfloor heating fitted. It works very well. Cost for an L shaped room 6m x10m was c£6k from memory. There was a lot of mess from the dust.

Take a look here: www.jk-gb.com/

There are many people that do not subscribe to the thought process that says you must dig half your floor up. The heat loss downwards from such systems isn't what some would have you believe. Have a chat with them - they're friendly and helpful.

As a underfloor heating designer and expert, an overlay system will suit you fine, they are thin thus don't take up much hight, don't believe most of the downward heat loss, if you pick the correct system this has little impact, and you can achieve the room temperature you are after with lovely warm floors.

As a technical Interior Designer, a screeded wet system is my preferred choice but it is invasive and time consuming. Depending on your subfloor, if concrete slab, this needs excavation, insulation (I forget precise mm to current regs) plus 75mm screed. Screed takes around a day per mm to dry unless accelerants are added which can halve the dry time , so still overall a lengthy operation. There are, however, polypipe wet systems which are very effective and involve laying boards with grooves pre-routed into them into which the pipes are inserted. Ideal for upper floors of timber construction and raises overall floor height by around 45mm. Ask an installer for information specific to your particular property. Just don't consider electric. Cheap to install, expensive to run any rarely sufficient output without additional secondary heat source. Generally fine for small bathrooms though. Good luck!

Hiya Moonshadow11
Reading most of the comments here from experts and people with experience with UFH, I would agree with them. We are a 3 generation family of builders, houses, extensions, renovation etc. We put in literally tons of the stuff, all over the place. Be very careful not to rush into anything, in my experience the key to wet UFH is the insulation, as you don't want to be heating the brick walls of your house or the world beneath, if poorly installed it can become very expensive and more importantly bad for the environment depending on your heat source. If someone asked us to retrofit wet UFH in a room/house, I'd be looking at excavating approx 200mm (8 inches in old money) below the existing finished floor level. Please get a professional round to give you advice. It would also be a good idea to have a heat loss calculation to determine the efficiency of what you want to do. Sorry to bore the pants off everyone

I've just finished doing my UFH. We didn't want to dig but wanted it to be insulated. Try www.warmup.co.uk/underfloor-heating/water/total-16. The water pipes sit in the insulation boards and you can put your flooring straight on top, but we added a extra membrane to avoid cracking as we have tiles and it's great. The floor was raised by 40mm in total

If you speak with snug underfloor heating, they are cheaper then polypipe and will only raise the floor by 18mm while providing a much nice thermostat, ease of use is important :)

Thank you for your input on this. Will take a look at the links posted.

If it’s too big a job will probably just get flooring that is warmer underfoot.