UFH and Screed

B

BMD

Registered User
Messages
133
Hi,

I just wanted to get people's opinions on the type and depth of screed to use with UFH. I have read and heard of a lot of contrasting opinions. At the moment I have spec'd for the following;

Downstairs
150 mm insulation (TF70) and UFH in 75mm of sand/cement screed

Upstairs
25 mm insulation (TF70) and UFH in 75mm of sand/cement screed

I feel that downstairs is probably ok as I am reluctant to use easyscreed (30mm) because I have heard it doesn't hold the heat well

I feel that 75mm upstairs may be too much as a quick response time may be more important here and therefore easy screed could be an option.

I would appreciate any thoughts and advice
 
Hi BMD,

I used 75mm concrete down stairs on 150mm insulation and 30-35mm Easyscreed upstairs
I find it works well. No issues with cooling down quickly either.
 
On the ground floor insulation we used 2 layers 70mm with the laps staggered, on the first floor one layer 40mm between the precast units and the screed
(some propose putting the insulation beneath the precast)

One thing I have learned to my cost when dealing with UFH / screed / precast units etc - figure out now all the opes you need for services / stove flues etc.
If they are not factored into the precast design then you may end up retro fitting trimmer steel around opes, like us.
Cast a blockout in the screed using a few layers of insulation, this can then be scraped out and the precast cored through.
Boots
 

Exactly correct. Downstairs is fine but upstairs is too thick. The response time will be too long for bedrooms. Circa 50mm would be the norm, dependent on the structure and type of installation.
 
And of course do not forget the membraine to be installed on top of the insulation to prevent concrete causing damage to the integrity of the insulation,seemingly a well kept secret!!
 
Hi bmd

I have ufh installed in my new build a year ago,and had the same questions and after much looking around i went with 50mm of easyscreed on top of ufh.it was the best thing i ever did,heat up time is fantanstic,much better where tiles are layed.
The house is 3000 sq foot and i only have my heating on for 3 hours a day (4.5 in winter) had a plumber here last week and he couldnt understand how the house was so warm with the heat been on so little.Have talked to people with sand and cement mix and there heat up time is much longer,as far as im concerned the screed is the way to go..
 
If you're retrofitting, you should seek a calculation from a chartered engineer confirming that the existing floor joists and construction can take the extra weight of the screed plus pipes plus water in the pipes, taking into account any notching or cutting that needs to be done or has been done.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
Completely agree. Structural calculations should always be carried out on both new build and retrofitting.
Notching joists should not be necessary as easy screed is normally laid on 19mm flooring grade plywood that is sitting on the floor joists.

[broken link removed]
 
Hi Shane,

True enough - I suppose I was referring to existing notching really. i.e. that the floor would be properly looked at by a competent engineer and not just be a calculation done remotely based on the owners measure of joist depth ignoring the condition of the timbers.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.
 
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