DIY UFH installation guide

[Simon C]

Hi, I’m hoping for a bit of guidance please!

 

I am considering installing a new ufh system myself in my own extension project,  and wondered if there was a post about it on here somewhere already? Or would anyone be able to direct me to a good, easy to follow guide about it for a fairly competent DIYer?

 

I’m a carpenter/joiner, so not a plumber, but know my way around a building site.

 

My old Victorian house has never had gas or boiler, only electric heating, so now the extension is underway, there will be a brand new plumbing system throughout, so no need to consider any existing plumbing/fittings, if that helps explain at all.

 

Thanks in advance!

[JohnMo]

Here's a few things to read

 

 

UFH-System-Design.pdf UFH output calculation.pdf

[SteamyTea]

As you are not using natural gas, have you thought of Air to Air Heat Pumps?

 

Regardless of what system is used, plenty of floor insulation will help, best to get it done early as it is hard to add it into a slab later.

[mistake_not]

For design I got a lot out of loopcad in a Virtual Machine so I could do repeated trails.

[Iceverge]

As you're DIYing for DHW I would recommend using Hep2O push fit. I thought it was excellent. A radial layout from the tank. 10mm pipe for everything except the showers, bath and kitchen/utility taps. Keep the UVC as close as possible to the kitchen tap. I preheated the hot manifold by convection by positioning it directly above the UVC. 

 

I'd have liked to have included a floor drain in every room with a pipe joint or a tap just in case of a leak. Next house....... 

[Nickfromwales]

On 25/12/2025 at 00:08, Iceverge said:

I'd have liked to have included a floor drain in every room with a pipe joint or a tap just in case of a leak. Next house....... 

Please mark on the calendar, each year from now until the next house, just how many times you needed the floor drains.

 

Then realise why nobody in the UK fits them. .

 

FWIW I am specifying a plant room with all plumbing in, with a new insulated raft, and I am  going to recess the slab by 25mm in there and add a drain (sump), plus I am going to spec Fermacel and then tank it and the slab. In the event of anything 'wet' giving up in the plant room, the water will just disappear 'down the plughole'.

 

The issue is, keeping these drain populated with water so the stink doesn't rise from the sewer, or worse (vermin etc). I'll install a gulley with throughput, so the constant use of the washing machine or utility sink replenishes the body of water in the trap. 

 

On 24/12/2025 at 12:19, Simon C said:

Hi, I’m hoping for a bit of guidance please!

 

I am considering installing a new ufh system myself in my own extension project,  and wondered if there was a post about it on here somewhere already? Or would anyone be able to direct me to a good, easy to follow guide about it for a fairly competent DIYer?

 

I’m a carpenter/joiner, so not a plumber, but know my way around a building site.

 

My old Victorian house has never had gas or boiler, only electric heating, so now the extension is underway, there will be a brand new plumbing system throughout, so no need to consider any existing plumbing/fittings, if that helps explain at all.

 

Thanks in advance!

Ask loads of questions, we will give the same amount of answers  

 

[JohnMo]

4 minutes ago, Nickfromwales said:

drain populated with water so the stink doesn't rise from the sewer

Or a dry trap?

5 minutes ago, Nickfromwales said:

recess the slab by 25mm in there and add a drain (sump), plus I am going to spec Fermacel and then tank it and the slab. In the event of anything 'wet' giving up in the plant room, the water will just disappear 'down the plughole'.

 

6 minutes ago, Nickfromwales said:

Please mark on the calendar, each year from now until the next house, just how many times you needed the floor drains.

One or the other sounds contradiction, or your client has money to waste🤔

[Iceverge]

1 hour ago, Nickfromwales said:

Please mark on the calendar, each year from now until the next house, just how many times you needed the floor drains.

 

Thus far the count is exactly precisely zero since inredid my new build with Hep2O. 4 years is a drop in the ocean though.  I'm still living with both excellent and average decisions from 1950-1960 on the farm from my grandfather. 

 

I reckon you could plumb a house for 100 years+ if you were clever. 

 

Imagine the satisfaction from the afterlife when your great great grandsprog says under his/her/it's/their breath:

"Wasn't great old grand Nick a clever C*nt." 

 

Floor drains with U bends that take a basin or shower in the side are more robust than airless traps in my opinion. 

 

Merry spannering. 

 

 

 

[Alan Ambrose]

>>> Ask loads of questions, we will give the same amount of answers  

 

Actually, we’ll give six different, sometimes mutually opposing, opinions for each question. 😉

[Beau]

I dont know if they still do it but when we built our place we used Chelmer Heating who did a design and supply for self installation. 18 years later its still working fine.

[Nickfromwales]

18 hours ago, JohnMo said:

One or the other sounds contradiction, or your client has money to waste🤔

One is indiscriminate, the other is a targeted and sensible insurance. A drain (singular) vs drains  

[Nickfromwales]

9 hours ago, Alan Ambrose said:

>>> Ask loads of questions, we will give the same amount of answers  

 

Actually, we’ll give six different, sometimes mutually opposing, opinions for each question. 😉

What he said.  

[Nickfromwales]

18 hours ago, JohnMo said:

Or a dry trap?

If you give these a decent flogging over the years they start to give up. I only use these for condensate or D2 these days, unless there's no other option, so they only see clear water and very low volumes or none at all (D2 in normal use is dry).