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I think I'm going to stick with what I've started which is the pipework clipping directly to the top of the celotex 25mm below joist top.

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On 27/06/2019 at 13:44, Toppers said:

I was going for this method:

dry-biscuit.jpg

 

I was talking to a heating engineer and he didn't rate the method above as being effective enough, has anyone any experience of installing/using this?

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Looks similar to what @ProDave has done

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4 minutes ago, PeterW said:

Looks similar to what @ProDave has done

If you mean using a biscuit mix as the heat spreader, yes that is exactly what I have done, only mine was above the joists and battens on top of the joists (with notches where needed for pipes to pass through)

 

My pipes are at 200mm centres with the biscuit mix and working very well. Engineered oak floorboards over the top.

 

But the house is well insulated so it doesn't need much heat anyway, but we did use the same system in the previous house with less insulation and it worked there as well.

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5 minutes ago, ProDave said:

If you mean using a biscuit mix as the heat spreader, yes that is exactly what I have done, only mine was above the joists and battens on top of the joists (with notches where needed for pipes to pass through)

 

My pipes are at 200mm centres with the biscuit mix and working very well. Engineered oak floorboards over the top.

 

But the house is well insulated so it doesn't need much heat anyway, but we did use the same system in the previous house with less insulation and it worked there as well.

 

So to clarify on top of the biscuit mix do you have chipboard or is the oak straight to the joists? My construction will be biscuit mix, 18mm caber board, tile backer board, tiles.

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1 minute ago, Toppers said:

 

So to clarify on top of the biscuit mix do you have chipboard or is the oak straight to the joists? My construction will be biscuit mix, 18mm caber board, tile backer board, tiles.

20mm engineered oak flooring directly on the battens. the gap between the battens filled with biscuit mix.

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8 minutes ago, ProDave said:

20mm engineered oak flooring directly on the battens. the gap between the battens filled with biscuit mix.

 

Do you think the heat will generate through the chipboard and tiles ok?

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14 minutes ago, Toppers said:

 

Do you think the heat will generate through the chipboard and tiles ok?

 

Yes it’s fine. With this build up I would just be going with a hardiebacker type board straight on the joists. 15mm stuff would be more than enough assuming your putting a good 50mm pug around the pipes. 

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50 minutes ago, PeterW said:

 

Yes it’s fine. With this build up I would just be going with a hardiebacker type board straight on the joists. 15mm stuff would be more than enough assuming your putting a good 50mm pug around the pipes. 

 

Had a quick look and they only seem to do 12mm in hardiebacker I've already set the joists to accept 18mm chipboard (I'm matching up to an existing floor) so this could be a problem.

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6mm ply then 12mm Hardiebacker would work then. 

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18 minutes ago, PeterW said:

6mm ply then 12mm Hardiebacker would work then. 

 

Yes that could work I'm not that familiar with hardiebacker is it a fairly strong material?

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It’s a cement board that is hard as nails. There are others, you can tile straight over it. 

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On 27/06/2019 at 13:33, ProDave said:

Okay as someone who did this (a little different) I wanted to be clear that you are putting battens along the top of the joists to support the floor, with the biscuot mix filling in between as a heat spreader, but not supporting the floor.

 

This solves the problem of how the UFH pipes cross the joists, you leave a small gap in the battons.  and it means you don't need much support for the celotex.

 

I take it the joists have been specified taking into account the extra dead load they have to support.

Did you just batten out on top of the joists and then screed or did you cover the joists first with ply or something then pipes with batten supports directly over joist positions and screed infill? 

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1 hour ago, Carrerahill said:

Did you just batten out on top of the joists and then screed or did you cover the joists first with ply or something then pipes with batten supports directly over joist positions and screed infill? 

OSB over the joists, battens on top following the joists, UFH in between filled with biscuit mix

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13 hours ago, ProDave said:

OSB over the joists, battens on top following the joists, UFH in between filled with biscuit mix

This is how I intend to do my first floor UFH.  18mm OSB on the pozi joists, batten out 50mm for the pug and pipes then 18mm caberdeck on top.  Final floor finishes on top of that.    

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Posted (edited)
14 hours ago, ProDave said:

OSB over the joists, battens on top following the joists, UFH in between filled with biscuit mix

Thanks,

 

19mm, 25mm batten? 

OSB over joist thickness?

 

I think I shall go this route Dave, so I need to workout my floor makeup - my joists are sitting in, loosely, to give me my temp working floor - with 11mm OSB on top for now - at that I am am about 10mm lower than the floor level of the rest of the house - minus any floor covering -  so I will need to reduce the plate the joists currently sit on by 19/25mm so that my FFL works out. 

 

 

Edited by Carrerahill

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