UFH design received - any tips on how to mark out the floor / install

[Great_scot_selfbuild]

Given the challenge of getting a UFH design done, now that we’ve (eventually) selected our UFH supplier, I thought I’d share the layout design they have provided. I had requested a spiral pattern and first time they sent over a serpentine design. I’m pleased I checked it as soon as it arrived as they they re-ran it and sent the spiral pattern, but I do like having both as a comparison.

 

We will be installing the pipework and now that we have a design to look at I’m interested in hearing advice on how best to tackle (practically) the layout. I’m purchasing a UFH staple gun and decoiler for the pipe.

 

I’ve got a couple of weeks before we start this. My initial thoughts are to mark out 150mm spacing across each room in both directions (partly to double-check the design), and lay the longest loops first.

 

Spiral configuration that we’re installing:

Close-up of the longest runs:

 

 

[Barnboy]

I marked my perimeter at the required spacings, then ran a chalk line from mark to mark to create a web pattern.

Next I took a permanent marker and followed the web around each room marking the turns of each loop. Once I was happy I had the correct layout according to the designs I took some line marker paint and drew each loop out over the challk line, turning ay each marker pen mark.

Once everything was drawn out and I was happy, as I was fixing onto concrete I marked and fixed down the pipe clips and started laying the pipe out from the manifold starting with the furthest loop from the manifold 1st and working loop by loop back toward the manifold in each direction until all loops were fixed down.

[Great_scot_selfbuild]

@Barnboy that is exceptionally helpful, especially with the photos added - very much appreciated. Chalk line ordered!

[JohnMo]

Couple of comments - because I can't help myself.

 

1. You have all loops transiting via what I assume is a hallway, then an additional 3 loops dedicated to the hallway. Deleted the dedicated loops and spread the pipes transiting through halls to provide hall heating.

2. Low temp heating will perform just as well with either spiral or serpentine.

3. Design is done on the premise of zoned heating, using a thermostat to control each area. Bit like adding the largest radiator you can fit on a wall in each room. As it is the floor array isn't designed for room heat loss, so balancing the heating will be battle.

3. Your pantry wants to be cold, I would keep all pipes well away from there by at least 300mm.

4. Assume your manifold is in or close to the utility, with all the loops transiting through that area, it will always be hot in heating season, you do not need a dedicated loop there. You will also need to think about adding insulation to pipes to prevent overheating. So 9mm insulation for the first 2m of each loop or run in 20mm conduit to thermally disconnect from screed for the first couple of meters.

5. Drawing by something selling products, not heating design. It isn't a heating design.

[torre]

Alternative to the chalk line is a membrane with a printed grid

[SimonD]

19 minutes ago, JohnMo said:

It isn't a heating design.

 

This.

 

1 hour ago, Great_scot_selfbuild said:

My initial thoughts are to mark out 150mm

 

There is a pattern here on buildhub that we see a constant stream of UFH systems all with 150mm space regardless of the house. So:

 

- do you not have a heating engineer working with you to design the ufh as part of the whole heating system?

- what has the supplier provided you in terms of design specification relating to floor output compared to heat load?

- and have they also specified lots of room stats

 

1 hour ago, Great_scot_selfbuild said:

Chalk line ordered!

 

Get an inkline instead - clearer marking on all types of substrates plus you get water resistant ink too. That way you can use it to do your full markup. https://tftools.com/blogs/product-advise/inklines-versus-chalklines?_pos=2&_psq=inkli&_ss=e&_v=1.0

[Susie]

I can recommend the lamb on heating grid @torre mentions it also acts as the slip membrane between insulation and screed. 

 

I also have the build hub UFH stapler if you want to borrow it.  The stapler is passed member to member, I would pay for postage to you and you keep for the next user and post to them. 

[Apache]

14 hours ago, SimonD said:

do you not have a heating engineer working with you to design the ufh as part of the whole heating system?

I'm not the OP and I won't be in this position for maybe 18 months, but my initial answer is no. There are so many companies offering to do, sometimes very simple things, for you for a fee, that I find it a minefield of who I should pay, who I should accept industry standard figures from and where I should lick my thumb and go by what I think sounds about right. 

 

I think all we all want is a nice warm house, that doesn't cost a fortune to heat. I drop into the category of wanting to do as much as I can myself. Are there individuals or companies recommended for heating design who don't then want to sell me anything or install themselves? 

[Nickfromwales]

49 minutes ago, Apache said:

Are there individuals or companies recommended for heating design who don't then want to sell me anything or install themselves? 

Yes. They're called M&E consultants.

 

These will take everything into account, and look at your heating demands holistically, including fabric and ventilation heat loss, heating emitter types, insulation and fabric standards, airtightness, oh...........and the other X factor........the good folk who actually have to live in it comfortably, afterwards .

[Great_scot_selfbuild]

10 hours ago, Susie said:

 

I also have the build hub UFH stapler if you want to borrow it.  The stapler is passed member to member, I would pay for postage to you and you keep for the next user and post to them. 

Thanks - I had read about this. I’ll DM you 😁

[Great_scot_selfbuild]

10 hours ago, Susie said:

I can recommend the lamb on heating grid @torre mentions it also acts as the slip membrane between insulation and screed. 

@Susie Thanks! - photos of it in use is really helpful. We have spoken to countless people about the screed options and I was surprised that I have been advised that for dry screed (which were going for) we don’t need a membrane/layer on to[ of the PIR insulation as, although it’s pumped in, it’s simply not as runny as liquid screed.

What type of screed did you lay on top? Either way, I like the approach of using the grid membrane @torre included a link to.

 

23 hours ago, SimonD said:

 

- do you not have a heating engineer working with you to design the ufh as part of the whole heating system?

- what has the supplier provided you in terms of design specification relating to floor output compared to heat load?

- and have they also specified lots of room stats

Our ASHP supplier is working on the heating load requirements, and the UFH supplier providing the UFH design.

I’ve asked for the additional design information beyond just the drawings, yes.

 

23 hours ago, JohnMo said:

Couple of comments - because I can't help myself.

@JohnMo 🤣 they’re welcomed! 🙏. Posting publicly is always a risk, and sometimes the best comments are those that challenge your (my) current position, either to present an alternative not yet considered, or to make sure the path chosen is done so in knowledge of the risks/compromises (which there always are), so thank you - very much appreciated 😁.

 

23 hours ago, JohnMo said:

1. You have all loops transiting via what I assume is a hallway, then an additional 3 loops dedicated to the hallway. Deleted the dedicated loops and spread the pipes transiting through halls to provide hall heating.

2. Low temp heating will perform just as well with either spiral or serpentine.

3. Design is done on the premise of zoned heating, using a thermostat to control each area. Bit like adding the largest radiator you can fit on a wall in each room. As it is the floor array isn't designed for room heat loss, so balancing the heating will be battle.

3. Your pantry wants to be cold, I would keep all pipes well away from there by at least 300mm.

4. Assume your manifold is in or close to the utility, with all the loops transiting through that area, it will always be hot in heating season, you do not need a dedicated loop there. You will also need to think about adding insulation to pipes to prevent overheating. So 9mm insulation for the first 2m of each loop or run in 20mm conduit to thermally disconnect from screed for the first couple of meters.

5. Drawing by something selling products, not heating design. It isn't a heating design.

1. I have wondered about this - why the runs to/from the loop aren’t also spaced as the same as the heating yrs serving the same function after all. I’ve not had any design / response look any different to this (nor seen ones do it in the photos I’ve seen on this group - they’re all bunched together in getting to their destination). I’m going to ask I again, but have low hopes that they’ll have the skill or wherewithal to do that. I’m getting used to the professionals’ not living up to expectations, even when they just specialise in that one aspect of design.

 

2. Noted.

 

3. Not sure I understand what you’re saying? (FYI the whole downstairs is single zone, and provides heating up through void in hallway for upstairs).

 

4. Manifold is in the utility, yes. This is the first I’ve had anyone mention insulating pipes, though it makes perfect sense - can you please elaborate? (Photo appreciated, to help me interpret what this looks like before screed is laid on top).

 

5. Yes, and yet this seems to be the way the industry operates. I approached quite a few M&E firms but the prices were quite ridiculous. Would be ha[py to pay a reasonable fee, but not how they marked everything up and tried to oversell. Rather made me very sceptical about the whole lot tbh (on top of me having to correct some of the professionals I have paid).the spread of inputs from this group helps me balance out the options and weight it all up. I agree, it isn’t a design.
 

 

[JohnMo]

8 minutes ago, Great_scot_selfbuild said:

 

3. Not sure I understand what you’re saying? (FYI the whole downstairs is single zone, and provides heating up through void in hallway for upstairs

The person that put the UFH drawing together, has assumed you will be having a fully zoned system, so each space will have a thermostat including the hall. That is why they bunch all the pipes together when transitioning through an area.

 

11 minutes ago, Great_scot_selfbuild said:

Manifold is in the utility, yes. This is the first I’ve had anyone mention insulating pipes, though it makes perfect sense - can you please elaborate? (Photo appreciated, to help me interpret what this looks like before screed is laid on top

This where the design comes in not making pretty images. You need to understand the heat output and space heat demand. Areas like the utility can be overheated very easily with so many pipes going through area. You need the so called designer to factor this in to the design - LoopCad will do this for you automatically. LopCad is a free to download and a month or so free to use. A weekend messing with is will have a good design done.

 

 

[JohnMo]

15 minutes ago, Great_scot_selfbuild said:

been advised that for dry screed (which were going for) we don’t need a membrane

The membrane does two things, stops thin fluid screeds from going under the insulation. But second stops a chemical reaction between the aluminium skin on the PIR and the cement in the dry or wet screed forming hydrogen gas.

[SimonD]

31 minutes ago, Great_scot_selfbuild said:

Our ASHP supplier is working on the heating load requirements, and the UFH supplier providing the UFH design.

I’ve asked for the additional design information beyond just the drawings, yes.

 

Okay, from the design you posted up you have a classic situation of tail wagging the dog. The ufh you have isn't a heating design, it's a geometric exercise of fitting pipes of a certain spacing into a define space. The heat loads need to drive the design of the ufh, just like the heat loads would drive the sizing of a radiator or fan coil. Really, I would expect the ASHP supplier (should be designer and installer) to be taking the ufh off your hands and co-ordinating to make sure the ufh is suited to both the house and the ASHP. 

[SimonD]

9 hours ago, Apache said:

I'm not the OP and I won't be in this position for maybe 18 months, but my initial answer is no. There are so many companies offering to do, sometimes very simple things, for you for a fee, that I find it a minefield of who I should pay, who I should accept industry standard figures from and where I should lick my thumb and go by what I think sounds about right. 

 

I think all we all want is a nice warm house, that doesn't cost a fortune to heat. I drop into the category of wanting to do as much as I can myself. Are there individuals or companies recommended for heating design who don't then want to sell me anything or install themselves? 

 

I know your dilemma well. It is exactly the reason why I learned how to design and install heating systems, and especially low temperature ones, and now have my own heating design and installation business! The industry is a mess.

 

But yes, there are companies around that can and will do a design and leave it at that. There are a few down south that offer this along side their own installations. Here is one that has a lot of experience and a good reputation, but I don't know their fees. Might be worth a call for @Great_scot_selfbuild:

https://robberridge.co.uk/self-build.php

[Nickfromwales]

4 hours ago, JohnMo said:

The membrane does two things, stops thin fluid screeds from going under the insulation. But second stops a chemical reaction between the aluminium skin on the PIR and the cement in the dry or wet screed forming hydrogen gas.

I've lifted quite a few failed floors, and the most I've seen is some darkening of the foil, nothing more severe, as the side effect of the screed going down onto bare foil covered PIR. I assume any off-gassing would be happening only during the curing process, with maybe a tiny amount thereafter (if any).

 

The biggest benefit of using the membrane with dry screed is to have markers to use to lay the pipe to. Makes life a lot easier, but I use the PIR that comes with the 100mm lines on it mostly, and favour dry screed, so not really needed afaic; (if liquid, then it's needed, yes).

[Nickfromwales]

On 28/02/2026 at 07:18, Barnboy said:

I marked my perimeter at the required spacings, then ran a chalk line from mark to mark to create a web pattern.

Next I took a permanent marker and followed the web around each room marking the turns of each loop. Once I was happy I had the correct layout according to the designs I took some line marker paint and drew each loop out over the challk line, turning ay each marker pen mark.

Once everything was drawn out and I was happy, as I was fixing onto concrete I marked and fixed down the pipe clips and started laying the pipe out from the manifold starting with the furthest loop from the manifold 1st and working loop by loop back toward the manifold in each direction until all loops were fixed down.

Great minds lol.....

 

[Conor]

As above, the self adhesive clip rails are great. Lay them out, stick them down, then start laying your pipe, dead easy to get spacing set. You need a few staples on the bends.

[Nickfromwales]

51 minutes ago, Conor said:

As above, the self adhesive clip rails are great. Lay them out, stick them down, then start laying your pipe, dead easy to get spacing set. You need a few staples on the bends.

I can't even imagine relying on the self adhesive to stay put during the pour. In the pic above, I gas nailed the feck out of each and every rail, and then went around with some P-clips where the pipe still refused to stay put.

[Great_scot_selfbuild]

10 hours ago, JohnMo said:

The person that put the UFH drawing together, has assumed you will be having a fully zoned system

They knew exactly what we planned to do and we gave a very clear requirement. I'm getting very used to this 'quality' of output from the suppliers / distributors etc. now though. Speaking to my builder, it's entirely 'normal' and he spends a large amount of time fixing design issues on site.

 

10 hours ago, JohnMo said:

LopCad is a free to download and a month or so free to use

Unfortunately it also only works on windows and I'm loathed to by a PC or try and set up a virtual machine on my Mac just for this; this was why I went with a supplier who would be paid to do the design (having provided them with all the necessary information). #sigh...

 

9 hours ago, SimonD said:

Here is one that has a lot of experience and a good reputation, but I don't know their fees. Might be worth a call for @Great_scot_selfbuild:

https://robberridge.co.uk/self-build.php

Is this a personal recommendation of this one, or has it turned up on a search (just wanting to make sure I understand before I look around). Thanks for the nudge.

 

5 hours ago, Nickfromwales said:

The biggest benefit of using the membrane with dry screed is to have markers to use to lay the pipe to

This is a good enough reason for me I think

 

 

[SimonD]

5 minutes ago, Great_scot_selfbuild said:

Is this a personal recommendation of this one, or has it turned up on a search (just wanting to make sure I understand before I look around). Thanks for the nudge.

No, I have his website in my bookmarks. I don't know him personally, but he is known in the industry,  and I'm in the industry - IYKWIM? He was actually interviewed by HVAC Education hub recently, so you can listen to him talk - he very much talks the language of buildhub in his design philosophy.