underfloor heating problems

G

griffandco

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Our builder dropped the level of three of our rooms by 2 to 3 inches thinking we were going to put battons to secure our timber floors. Concrete is now poured over our underfloor heating so no going back.Question is can we pour another layer of concrete to have our floors level or will this affect the effeciency of our heating?
 
griffandco said:
Our builder dropped the level of three of our rooms by 2 to 3 inches thinking we were going to put battons to secure our timber floors. Concrete is now poured over our underfloor heating so no going back.Question is can we pour another layer of concrete to have our floors level or will this affect the effeciency of our heating?
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So how many inches will be covering your UFH pipes? 6" i'm guessing, which to me sounds why too much, 3-4" would be maximum imo. I

assume by concrete you mean screed? in which case I think you should consider lifting it and adding extra insulation to make up the difference and redo the pipeworth in the 3 rooms.
 
Sounds like a right screw up by your builder and/or your architect. I'd try to get him to fix this at his own expense. You're going to have to take up the lot.
 
that is some balls, under no circumstance would I go about the 4" of screed, it bring up your responses times way to much
 
i recently put in ufh and was worried about this as i have about 6 inches of cement over it. my worries were totlly unfounded. response times are a little slower than rads but from cold, you can feel the room getting warmer within an hour or 2, way before the tiles start to feel hot. last week we ran out of oil on a sunday morning and there was still noticeable heat in the floor at lunchtime the next day when the oil man came. this has got to be due to the thick screed. ufh really is light years ahead of rads.
if you are bringing your levels up, i would roughen the existing surface up before pouring and bring the ufh on very slowly initially.
 
Hi xt40 - apologies this is off-topic ..

You are using oil to run your UFH - how do you find this cost wise?
I'm getting ready for a self-build, want UFH but still have to decide how to run it - thx
 
xt40 - When you say "hot" I presume you mean warm? What temp is your UFH running at?
 
not sure yet about the costs as its only been up and running for a couple of weeks and there was some oil in the tank from last year. il run the tank dry and that will give me some idea. whatever it costs, it is worth it.
regarding the floor temp. we vary it to speed up the response time but probably use 30-35 most of the time (range is 25-50) even at 25, the difference underfoot between the kitchen/dining area (ufh) and the utility(rad) is huge
 
I presume that is the flow temperature & not your room temperature!!!
 
You must have very tight loops to get it down to 30 degrees, most installations run about 40 degree, otherwise you would not achieve the 20c in the room temperature.
 
On a technical point, even if you were to pour an additional screed over the exist slab this may pose a problem from the point of view of cracking or curling of the topping. Thin screeds (less than 4") can crack, delaminate from the substrate (too thin and too light) and in extreme cases- curl at the edges. Such screeds wear poorly and give trouble. You won't be able to achieve a great bond with the existing base if it is already too well cured. To avoid all this you will need to incorporate a light mesh or fibre into your screed topping. I'd imagine the UFH would exacerbate the effects noted above if some precautions were not taken. These defects are most likely on large floor screeds.
 
yop said:
You must have very tight loops to get it down to 30 degrees, most installations run about 40 degree, otherwise you would not achieve the 20c in the room temperature.
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yes the loops are fairly tight and i also used high quality foil backed insulation. at 30 it rarely goes over 17-18. when set to 40 it can go a good bit higher. im still at the experimenting stage
 
xt40 said:
yes the loops are fairly tight and i also used high quality foil backed insulation. at 30 it rarely goes over 17-18. when set to 40 it can go a good bit higher. im still at the experimenting stage
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Aye, we did the same as yourselve, have loops from 25mm, means we are running at 28 deg c for the flow rate, it keeps the running costs down big time!!

The way you could get away with a thin screed is to put batten down and pour between, at least the weight will be carried on the battens
 
yop said:
The way you could get away with a thin screed is to put batten down and pour between, at least the weight will be carried on the battens
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Don't really understand what this will achieve? You are effectively introducing even thinner weak spots in the screed if you go this route, and to no effect. The screed will crack at every batten location and the battens serve no function anyway.
 
as i already said, roughen the surface sufficiently (with a scarifier) and there shouldnt be any problems
 
Carpenter said:
Don't really understand what this will achieve? You are effectively introducing even thinner weak spots in the screed if you go this route, and to no effect. The screed will crack at every batten location and the battens serve no function anyway.
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The battens would act as your weight bearers, with your screed as a "filler" in between.
Only good though if you are going the timber route on the floors.
We did that upstairs in our shack and it works grand.
 
Still havent decided what to do...he who hestiates etc., but three options seem evident from replies;
a) Leave the floors with a drop 0f 2 to 3 inches (call it a feature!)
b) pour additional screed and glue timber floors (we hope to put solid)
c) Pour screed with battens at intervals to secure timber floors
Is there an option I'm missing?
Also heard various stories re. solid timber and UFH would like to go this route if possible.
 
griffandco said:
a) Leave the floors with a drop 0f 2 to 3 inches (call it a feature!)
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If you decide to go this route don't have a 3" step just inside a door, it would be a disaster, anyone walking in the door would stumble, have an area inside the door at the hall level before the step.
 
Thanks for all tips re. dropped floors.
Think Yops reply of battens sounds like the answer to our prayers as we are putting down solid timber floors.
Few Q's re. Yop solution..
Was it solid timber & nailed to battens over concrete floor with UFH?
How long ago did you get it done?
Bit worried re. extra screed bonding to existing baseas Carpenter warned.
Any ideas as to what to pour here?
Builder suggests sand / cement mix.
How does this go with UFH
 
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