Best Perimeter Insulation for UFH

[Trw144]

What's the best perimeter insulation to use with my screed? I need to get it prepped for a few weeks time. Do I stick with the standard foam stuff? Are there suppliers of a thicker version?

[Trw144]

Anyone? You can't all have been watching the football

[Nickfromwales]

I believe PUR has slightly better value per mm so I'd go with 25 or 50mm of that. 

[Trw144]

Presumably it will have enough compression to allow for expansion? Also, can you tile over it with ditra mat as I'm going for shadow gaps and therefore tiles will butt up against the wall

[Nickfromwales]

You can tile 'over' it, but not to it . I'd not rely on it for expansion, but still fit the Ufh suppliers one after the PUR. 

At point it'll be soft, but over a few m's it'll be quite resilient imo so I'd fit both. On that pretence I'd prob go for 30mm + the Ufh exp skirt. 

[Trw144]

So ditra mat over it with the tiles should be fine?

alternatively I play safe and just add the ufh perimeter 

[Trw144]

Won't start a new topic but will tag onto this...

 

I need to order some insulation to fit between my 25mm battens onto which the aluminium ufh plates will be installed. Based on the 25mm batten, would 75mm rockwool provide the right balance between compressing enough so that it physically fits, but still providing enough upwards pressure on the plates so that they ensure good contact with the floor above?

[Crofter]

If you compress it to a third of its thickness, won't that greatly reduce its effectiveness as an insulator?

[Nickfromwales]

In this instance it's not being used primarily as an insulator . This is just to keep the spreader plates proud to ensure the floor is in good contact with them when it gets fixed down. 

Having the spreader plates sagging under the floor would be catastrophic in terms of transferring heat to the deck, and therefore the room. Not so much of an issue when you can get underneath to staple the plates up from underneath, but essential if you can't. 

[Woodgnome]

On 21/06/2016 at 10:48, Trw144 said:

Presumably it will have enough compression to allow for expansion? Also, can you tile over it with ditra mat as I'm going for shadow gaps and therefore tiles will butt up against the wall

Can you elaborate on how you are doing the shadow gaps?

What's your wall build up?

Cheers 

[PeterW]

Concrete thermal expansion is a myth.... From 8-35c it's about 0.0004m/m - it's contraction as it dries is a different matter and this is where the "expansion foam" comes into its own as it compresses slightly when poured due to the pressure of the concrete and then contracts as it dries. 

 

 

[Trw144]

12 hours ago, Woodgnome said:

Can you elaborate on how you are doing the shadow gaps?

What's your wall build up?

Cheers 

Wall build up is 140mm timber frame filled with 120mm pir, additional 30mm pir, vapour/air barrier, 25mm battens, plasterboard and final skim.

My plan is to tile the floor downstairs/lay the wooden floor upstairs. Then i will fit the renderplas shadow gap profiles and have it boarded onto these before final skimming. I should be attempting next month if you have time for me to be a gunea pig first.

Edited July 21, 2016 by Trw144