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!!!
 
your construction is not perfect.

you should have poured a 4 inch subfloor over the radon barrier and then insulated, installed UFH pipes and poured screed.... perhaps that type of UFH you are using doesnt allow for this.... but what you are going to end up with is 5 inches of concrete the UFH has to heat before distributing heat into rooms. This isnt a good thing, it reduces responsiveness of the UFH.. which is slow anyway. Have you passive vents???
 
no, i plan on putting in a HRV system.
considering that the make up is less than perfect, what would you recommend at this stage?
i could take up the piping and insulation and put in about 3 inches of subfloor, but this seems thin....
or more insulation to make screed thinner.

as a matter of interest why is it important to put a subfloor, would the well compacted hardcore and blinding not be supportive enough?
 
depth of subfloor is something your engineer would have to sign off on.
during my build engineer would only sign off a 6 inch subfloor so i guess it depends on what your engineer would sign off.
 
endag. said:
as a matter of interest why is it important to put a subfloor, would the well compacted hardcore and blinding not be supportive enough?
Click to expand...

mikeor is correct, generally a 6 inch concrete floor is required, although some engineers will sign off 5 inches.
The point is that you need this thickness anyway... therefore the 4 inch subfloor and 2 inches screed is the best situation.
You dont really have any option if you are not going to take up the pipes.... if you are then you have a few options.
 
ok, i will obviously need to get back to the engineer, but in the mean time,
if i take up the insulation and/or the pipes what's d best option?
I reckon the inconvienence would be worth it to get it right! if not i guess i just pour a thick screed and hope for the best....
 
i would take up the pipes and aeroboard.

I would lay another row of 65mm filler blocks around both leaves of the cavity wall

I would pour a 125mm subfloor, lay the 120mm aeroboard.. leaving you with 74mm... lay the UFH pipes.
Then pour a wet mix 30N concrete screed over the pipes bringing the finish level with the top of the filler blocks.

refer to here for explainations behind the advantages of a thinner screed:
http://www.askaboutmoney.com/showthread.php?t=65287
 
"I would lay another row of 65mm filler blocks around both leaves of the cavity wall"

sorry sydthebeat, do you mean 65mm of aeroboard? not sure, and do you mean both inside and outside the the wall??? i might be being obtuse...
 
just did my sums, so your suggestion is to lay another layer of blocks to increase the depth i have to work with, which will allow me to get the desired finish... can i lay this layer on top of the radon/DPM ?
 
following much discussion and advice from engineer and underfloor suppliers i have opted to raise the walls by a block on the flat and put in a subfloor of 160 followed by insulation of 120 followed by ufh pipes and screed of 74...
thanks for the advice sydthebeat, now i just have to tell the plumber the good news!!
 
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