UFH depth of screed etc. aargh

E

endag.

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going around in circles and need opinions/advice about underfloor having read previous threads.
have hardcore, blinding, radon barrier, 120mm aeroboard platinum.
yesterday i put underfloor piping on top of the aeroboard.
i have 134mm left to get level with the external walls.

option 1: easiest
if filled with concrete that would be about 5 1/2 inches of concrete so im just wondering if that is too much? my plumber thinks this would be ok.

option 2: pain in the ass
the other option would be to take up the piping (half days labour to put down) and put another layer of 60 mm aeroboard (cost of additional aeroboard) which would leave the screed at 74 mm. worth it?

option 3
having read other posts i have decided not to put battens and solid wood floor above a 74mm screed, due to its stopping of heat travelling up.

i have also heard of putting a concrete sub floor, then insulation then screed, but this would be difficult at this stage....

is the makeup of layers ok? i have heard/read a lot of different opinions.
is 5 1/2 inches of a screed ok?

what do you think, its these things would have you awake at night!!!
 
endag. said:
option 1: easiest
if filled with concrete that would be about 5 1/2 inches of concrete so im just wondering if that is too much? my plumber thinks this would be ok.
Click to expand...

I have to say I think your plumber's an idiot. 5 1/2 inches of concrete is way too much, and would be very slow and expensive to heat. Max for this screed should be 75mm, less (~65) if possible. Has this plumber ever dealt with UFH before??
How did it get to this unfortunate stage anyway that the levels are so far out!?
 
Option 1: Ridiculous, as for the reasons bobby04 gives. You might also need a special mix of screed to prevent cracking, etc.
Option 2: Probably the most obvious, assuming you don't want to go for option 3.
Option 3: Battens and timber flooring don't stop the heat going upwards. It's quite a common way of doing timber floors (and means you can get at the piping if necessary without having to rip up screed). These suspended systems have piping laid into an aluminium plate between battens, with minimum 25mm insulation between battens and directly under the plates (which also helps support them and encourages the heat to dissipate upwards rather than downwards). Just make sure the timber boards have adjusted to the normal indoor room temperature prior to installation.
 
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