Replace Pine Boards Over Wet UFH

[Benguela]

Hi Everyone,

 

I've got a big (50 sqm) groundfloor space in my house that is floored with pine boards over wet underfloor heating. The rest of the house is ceramic tile over the same wet UFH.

 

I didn't do the floor myself... bought the house like that... and I now want to replace the pine boards because not much heat is getting through from the UFH.

 

I've got the original UFH installer's plans. They date back to 2004 when the UFH was laid and they call for (from bottom to top) hardcore, then a damp proof membrane, then the structural floor slab, then insulation board, then UFH pipes in 65mm of screed. 

 

I've lifted up one of the pine boards to see how the floor is laid and we've got battens that are chased into the screed... not quite an inch thick, maybe 15 or 20mm... and the pine boards screwed to the battens. So what we've got is the heated screed, then an air gap, then pine boards. To my mind, that is wrong because the air gap means the heat doesn't transfer from the screed upwards and the pine doesn't conduct heat very well anyway. Am I right that this is pretty poor?

 

I would love to have a limestone floor, and got a quote, but the guy wants to break out the battens (price per hour of labour), get a specialist in to level the floor with latex for £1400, then charge me £50 psqm for labour to lay the stone tiles that I supply (they cost me about £40 sqm). So the whole job quickly comes to >£6,000.

 

I'm now considering engineered wood that I lay myself. 

 

Questions:

 

1. I'll get engineered wood that is specced to work with UFH... any suggestions for what to go for or avoid? My heating adjusts with how cold it is outside and my buffer temp varies on a heat curve between 30C and 40C.

2. To lay it, I can see three options

2.1 Keep the existing battens (after all, we know they are level). Fill in the gaps between the battens with low tog underlay like Duralay Heatflow. That will fill up the air gap and make sure the heat transfers through from the screed. Then secure my new engineered wood floor onto the battens with glue.

2.2. Break out the existing battens. Use self levelling compound (brand suitable for wet UFH) to even out the floor. Glue the engineered boards down onto that.

2.3 Break out the existing battens. Roll out an underlay (brand suitable for wet UFH) and trust that it's going to even out the floor enough. Then float the engineered boards over it.

 

What do people think? 2.1, 2.2 or 2.3?

 

Thanks for any advice as never attempted a floor before.

 

 

 

 

 

Edited November 27, 2021 by Benguela
Spelling

[JohnMo]

Underlay even with the lowest tog will insulate, so will be no better or worse than you are now.  So you options are, to either breakout the battons, or fill between.

 

You may need to look at the other floor levels in adjoining rooms, as you would want them to be as level with your new finished floor as possible.

 

Once you get started the battons could come out quite easily, then infill with a self leveling compound.  Engineered wood floor would then be glued down.  I was advised that floating the floor wasn't the best for heat transfer, as you have another insulation layer and air gaps.

 

So 2.2 would be the best option

[ProDave]

Keep the battens.  Fill any void with dry mix sand /cement 5:1 tamped down so it is level with the tops of the battens not above them.  Then lay your engineered board fixing to the battens.

 

[scottishjohn]

what are they UFH pipes laid on ?

 if not good thick insulation ,then most of your heat will going down 

so first job is as thick a layer of pir as you can get under UFH pipes ,

if you can jack them up to be touching new flooring ,then it will transfer the heat into the floor ,

even if the pipes stick up 10mm from floor joist  then floor boards should compress them tight to the floor once you lay new flooring -fill round them with biscuit mix or something --that will spread the heat above the pir 

 

thick insulation between sub floor and pipes is the way to go  and pack it tight including the edges so there is no air movement or drafts under there 

[Benguela]

Thanks for comments, guys.

 

Scottishjohn, the UFH is in 65 mm of screed. And under that screed, we've got insulation board.