DIY overlay boards for ufh

[EatingSnakes]

Hey guys.

Long time reader, first time poster.

I've got 42mm between my current concrete slab (insulated) and my desired final floor level (tiles)

How do I overlay my pipes?

Is there a thin screed that can be applied over the pipes?

Alternatively I was thinking of making some DIY overlay boards. I got the idea after reading about chipboard overlay boards and thought that I could make overlay boards out of plywood.

I would cut 18mm plywood in strips of 200mm and wedge the 16mm pipes in between each strip.

Each strip would be screwed into the concrete.

The plywood would then be primed and tiles laid directly onto the plywood.

The pipes would have plywood on both sides, concrete underneath and tiles directly above.

The total amount of space that needs underfloor heating and tiling is 4.5 sq m

Any advice would be much appreciated.

ES

 

[Dumbo]

Don't use plywood. Use Hardie backer board . 6mm + 12mm glued and screwed .
Wood is not a good surface to tile to . I'm not saying this will work but it will be better than using . You could also consider putting 6mm insulation board underneath . Unless I've missed something you have room .

 

[Spare Tool]

16mm pipes plus 15mm tile and adhesive (guessing at 10mm for tile) so only need to make up 11mm, just pressure up pipes and stick a few 11mm height markers and pour a flexible leveler on till you hit the markers..

 

[EatingSnakes]

Thanks for that mate.
So that's 26mm I've got to fill.

Any cheap and cheerful levelling compound you recommend?

I've also heard that standard sand cement render with some sort of fibreglass additive is strong enough at much smaller thicknesses provided its bonded directly to the slab.

Anybody have any experience with this?

 

[Spare Tool]

3 maybe 4 bags of mapei renovation screed from Screwfix should do it..

 

[Dumbo]

Do not try and just do cheap and cheerful or you will end opening it twice . That is to thin for sad and cement especially with heating . As above mapei renovation has a good rep

 

[Flintstone]

I think you should have a realllllly good read on this forum before you starting jumping in and using ply wood and cheap materials.

 

[Glynn]

I would also bring to your attention of, who would the guarantee be with. What you are going to do is making up your own UFH system that does not have any testing results to back up its performance. Check with your chosen leveller manufacturer first but don't be surprised if you get a "No".

 

[Spare Tool]

I would also bring to your attention of, who would the guarantee be with. What you are going to do is making up your own UFH system that does not have any testing results to back up its performance. Check with your chosen leveller manufacturer first but don't be surprised if you get a "No".

Is what it is though really Glynn...back in the real world we get advised by certain manufacturers to looselay 9mm ply over ufh or pour a cement based latex over aluminium foil, sometimes you just gotta do what you know works..

 

[J Sid]

clean and prime concrete
slc to a level 38 mm below ffl
prime and fix http://www.*************************.com/insulation-boards/water/25mm-solid-floor-panels
do pipework
prime and tile

 

[Andy Rhodes]

Is the 16mm pipes already in situ

 

[J Sid]

clean and prime concrete
slc to a level 38 mm below ffl
prime and fix http://www.*************************.com/insulation-boards/water/25mm-solid-floor-panels
do pipework
prime and tile

if you copy and paste http://www.*************************.com/insulation-boards/water/25mm-solid-floor-panels to search engine you will be able to work out what the link is

 

[EatingSnakes]

Thanks for the replys fellas
Very insightful.

3 maybe 4 bags of mapei renovation screed from Screwfix should do it..

This sounds like the best option to me.
So I can lay the pipes on top of the concrete and then poor the renovation screed directly above the pipes to the required level?

I have been recommended something like this too:
Concrete & Screed Fibres - 900G bag of 18mm polypropylene (PP) fibres 5060442883055 | eBay - https://www.ebay.co.uk/itm/Concrete-Screed-Fibres-900G-bag-of-18mm-polypropylene-PP-fibres-/141736144766

Does anybody have any experience with using Polypropylene fibres to make thin sand + cement screeds?

Thanks again

ES

 

[Andy Rhodes]

Julian cannot open that link keep getting an error code

 

[EatingSnakes]

you have to copy and paste the text into google mate. Its the first link.

Those ready boards are a good shout but it'll work out more expensive I think. I'll need 5 boards @ £25 each and levelling compound underneath them.

The Mapei looks good and it'll give better heat distribution.

I've already got lots of sand and cement and was wondering if I could make my own screed reinforced with PP fibre and SBR to fill 26mm worth of space.
Standard screed would definitely curl but I have heard good things about PP fibre.

 

[J Sid]

don't open it, copy and paste it to google and it will be on page one

 

[J Sid]

I've used this system many times

 

[Spare Tool]

Thanks for the replys fellas
Very insightful.



This sounds like the best option to me.
So I can lay the pipes on top of the concrete and then poor the renovation screed directly above the pipes to the required level?

I have been recommended something like this too:
Concrete & Screed Fibres - 900G bag of 18mm polypropylene (PP) fibres 5060442883055 | eBay - https://www.ebay.co.uk/itm/Concrete-Screed-Fibres-900G-bag-of-18mm-polypropylene-PP-fibres-/141736144766

Does anybody have any experience with using Polypropylene fibres to make thin sand + cement screeds?

Thanks again

ES

Ah I wrongly presumed your pipes were already fitted into pregrooved boards, like a polypipe type of system so the whole floor was already 16mm higher than the base, you need some sort of insulation under the pipes or you'll be wasting heat into the subfloor.. As it is it'd take a lot more than three of four bags of leveler, more like 10..

 

[J Sid]

where are the pipes coming from? Please don't tell us from your radiator run

 

[Time's Ran Out]

@JulianSidney - Plumb centre!

 

[J Sid]

to much time down south John and you have a developed a sense of humour

 

[EatingSnakes]

Ah I wrongly presumed your pipes were already fitted into pregrooved boards, like a polypipe type of system so the whole floor was already 16mm higher than the base, you need some sort of insulation under the pipes or you'll be wasting heat into the subfloor.. As it is it'd take a lot more than three of four bags of leveler, more like 10..

The concrete slab is already insulated underneath with 100mm PIR.

I was planning on putting overlay boards on top of the concrete and tiling directly on top of that. I was going to do DIY overlay boards, but now that I've realised I need to bring the floor up by 26mm, overlay boards won't cut it. Might as well reap the advantages of a screed. My calculations suggest I will need 6 bags of the Mapei screed :S

where are the pipes coming from? Please don't tell us from your radiator run

No, the pipes will be coming from a manifold although I have been given the option of a Danfoss TRV by my plumber. This basically feeds into the radiator flow. The idea is that because it is such a small space (4.1 sq m or ~30m pipe run) the boiler pump will be more than adequately be able to cope with it.

 

[Andy Rhodes]

So your plumbers saying you can run the system via your radiator valve because that's what a Danfoss TRV is a normal radiator valve. Is the manifold linking up direct from the boiler

 

[J Sid]

I'm not a plumber , but I wouldn't want radiator temp water flowing though my ufh pipes

 

[Andy Rhodes]

if the boiler is controlling the ufh it would have to be on to heat the floor up wouldn't it, because a boiler only has 2 setting on it heating & water or water only, I'd possible look at installing an electric ufh system preferably the matting one

 

[EatingSnakes]

nah. It's not an actual radiator TRV.

It's something like this:
https://www.polypipe.com/housing/po...rlay™/polypipe-ufh-temperature-limiting-valve

That one is made by polyplumb specifically for underfloor heating, it only allows the maximum appropriate temperature for UFH. I hear the Danfoss ones are better because it measures all of the temperature inside of the valve and you dont need the probe.

Anyway, back to the topic.
Will the Mapei screed work?
Does anybody have any experience in making fibre reinforced screeds for thin (26mm) ufh screeds.

Thanks for all the help thus far.

ES

 

[Spare Tool]

I'm no plumber either but surely that valve doesn't reduce rad water temperature it just opens and closes letting bursts of pipping hot radiator temperature water through, its not actually regulating the water temp? @Wayne Brown
The Mapei Reno screed is perfect but I still think you require some insulation under the pipes, even if its just 6 or 10mm Jacoboard or similar..what you board with is saving on leveler so hardly a difference in cost..

 

[Andy Rhodes]

You may have to fit anti fracture matting on top of the screed before tiling to compensate for the extra heat your system is going to generate

 

[Boggs]

You can use the Danfoss FHV valves when extending systems up to 10 sqm but I believe you need a minimum of 75mm screed.

 

[Time's Ran Out]

to much time down south John and you have a developed a sense of humour

Away from this pool tomorrow after 6 weeks! They’ve run out of mosaics.
I’ll be back.
But going down to Reigate for a week thanks to @stonetiler who has helped me fill in some time.
Wife doesn’t think it’s funny!