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Discuss UFH Joist system and Manifold selection - Evohome in the Water Underfloor Heating Installations area at

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Evening all

I have been researching the hell out of this, following my last project. Currently ripping half the kitchen out to remove a wall and make our downstairs open plan - If you wouldn't mind me running my plans by you to hopefully pick any obvious holes in.

Current floor is standard T&G boards with decent sized 400mm centre joists with a relatively short span for the vast majority. The initial plan is to create a UFH ring in the current kitchen, another ring in half of the living room which the kitchen will become part of once the wall is remove, and future proof for when the main part of the living room and extension get built.

Current thinking is to remove the floor boards,screw batons to the joists and fit 75mm Kingspan or similar 25mm below the floor level. After jostling over aluminium plates and realising i need to refit with glued edged chipboard (18 0r 22mm?), i figure i am best making the most of the efficiency below the boards, going for a dry biscuit mix instead of the plates for thermal mass - any tips on how long this will take to settle/dry before refitting boards? I will be using 16mm Pert Al Pert pipe held down with plastic clips to the insulation, neither ring will be more than 75mtrs.

I am running a full Evohome set up using Opentherm, so will be buying the HSS80 controller, or at least fitting a relay switch to start with (on a single stat) to power the UFH actuators (2 to start with) and pump, then wiring in an AO valve in parallel to my current AO CH valve, both designed to close when HW is on demand. The actuators will be standard AClosed 2 wire, no brand preferred but presume they are all relatively the same given that they are simply on/off switches, as long as i get the thread right.

My current dilemma assuming the above is ok, is the manifold. I note there's several price points available and believe you generally get what you pay for - current thinking is either an Emmeti unit EMMETI 5 PORT MANIFOLD WITH GRUNDFOS PUMP MIXING SET And 16MM MLCP PIPE CONNECTORS

Or an IVAR 6 Port Underfloor Heating Manifold with Uni-Mix Temperature Control Valve and Grundfos UPM3 Pump | Underfloor Parts The IVAR being about £80 cheaper and with a better pump (ignore price in link). I want to know opinions on this and if i am missing any other obvious options. I will add, I want to stay away from pushfit given the extra cost of the 15mm pipes and difficulty in bending for UFH purposes.


Last edited:

Uheat – Jake

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Hi Tim,

The system you've selected to use is a good idea however I'd double check your joists can take the extra weight of the sand/cement mix as it can be up to 30kg/m2 you'd be adding to the joists.

Manifolds are as you mentioned, quality is expensive. We have our 6 port kit with UPM3 and ESBE mixing valve for £447.53 IncVAT on our website.

If you'd like a detailed quote please feel free to give me a call.

01394 593305


You would need to batten the joists then ply on top then kingspan I can't see the weight being a problem if the joist have short spans,
We use 30mm pug screed and usually leave it a week before covering it's quite dry so you could get away with less time.
Aluminum plates are an absolute ballache especially when other trades walk over them and the pipes pop out of the grooves:mad:
We clip the pipes to the top of the joists and then cover with flat aluminium plates so much easier;)
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Thanks chaps

I have 400mm centres as mentioned, but the first 3 metres of joists are only 47x120 (3.3m long) with a lower wall support and cross members. So with 75cm Kingspan and 25mm supports and Pug screed gap... I have nothing left (ignoring the 5mm overshoot). Will the 75mm kingspan not take the weight of the mix?

Also, the Honeywell Evohome doesn't seem to require the temp sensor fitting within the floor for the stats, is it worth embedding one and leaving the wires loose? for the sake of a tenner... and where within the screed would you mount it?

C5 2400x600x18 chipboard is about to be ordered from Wickes, surprisingly the cheapest I could find locally! (Sheffield). Kingspan/Celotex next, just need to work out which type...

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