UFH in hollowcore structural topping?

[kxi]

Our design has a first floor of hollowcore planks (about 150mm thick) with a structural concrete topping (minimum thickness 50mm I think), and we are looking to add UFH.

 

Naively, it seems to me simplest, thinnest, lightest, and perhaps cheapest to have the UFH pipe laid in this structural topping and then make the topping the required thickness above the pipes (60mm?). As opposed to having; hollowcore, 50mm structural topping, then a separate (60mm?) screed with UFH over the top of that.

 

As I understand it, a structural topping over hollowcore is partly to create a smooth level surface, but also sometimes to create a composite floor with the precast planks, which is stronger.

 

My concern is that having UFH pipes in this topping would somehow adversely affect this structural aspect. I know there is general acceptance (on this forum at least) of UFH in structural ground slabs, such as in MBC builds, but what about as part of hollowcore floors? This is one for the SE, but would be keen to hear people's views.

 

 

[nod]

 You should be able to lay your insulation directly onto the hollow core Then add the UFH and screed 

Your SE may require you to point the v shaped joints prior to insulating 

[Ed Davies]

Is this a first floor in the UK or US sense?

[scottishjohn]

11 hours ago, kxi said:

Our design has a first floor of hollowcore planks (about 150mm thick) with a structural concrete topping (minimum thickness 50mm I think), and we are looking to add UFH.

 

Naively, it seems to me simplest, thinnest, lightest, and perhaps cheapest to have the UFH pipe laid in this structural topping and then make the topping the required thickness above the pipes (60mm?). As opposed to having; hollowcore, 50mm structural topping, then a separate (60mm?) screed with UFH over the top of that.

 

As I understand it, a structural topping over hollowcore is partly to create a smooth level surface, but also sometimes to create a composite floor with the precast planks, which is stronger.

 

My concern is that having UFH pipes in this topping would somehow adversely affect this structural aspect. I know there is general acceptance (on this forum at least) of UFH in structural ground slabs, such as in MBC builds, but what about as part of hollowcore floors? This is one for the SE, but would be keen to hear people's views.

 

 

or use an insulated type conrete floor set up and just uFh into that 

 there are lots ofsystems now where you use insualtion as the base for the concrete floor /roof 

https://www.quadlock.com/ICF-Floors-and-Roofs/quad-deck.htm

one of many 

izodom2000--ukagent is in scotland 

https://www.econekt.co.uk/wp-content/uploads/2016/02/ECONEKT.-ICF-Elements-Brochure2.pdf

see page 35 

i,m sure lots of others as well

Edited October 6, 2019 by scottishjohn

[kxi]

Thanks all of the comments. Thinking about it today, I think there's flaw that in our case means we can't use the structural topping to lay the UFH pipe.

 

The planks are laid on the bottom flange of asymmetric steel beams in a 'slim floor' style, in order to save height. e.g.

(based on shallow-floor designs such as https://www.steelconstruction.info/Floor_systems#Shallow_floors)

 

Since the structural topping doesn't in our case go over the top of the steel beams, the UFH pipes can't go through the beams (without complexity).

 

However, if anyone is ever interested in UFH pipes in hollowcore topping, it does appear that it is (or at least was) tacitly supported by US and Canadian building codes:

http://www.healthyheating.com/Concrete-codes-radiant-heating/Concrete-codes-radiant-heating.htm#.XZpJr0ZKhhF

 

The middle one was what i was thinking of. 

 

@scottishjohn 

The ICF floor style is neat and something I would have looked into, but in our case this floor is over an agricultural-use ground floor, which could have vehicles, workshops, storage, etc in  and I am very concerned about the effects of a fire down there on the house above. Any EPS in the floor soffit I would expect to last hardly any time before melting. In the EKONECT and quad-deck examples it looks like the EPS in the floor doesn't provide any structural aspect, as that's all handled by the cast/pre-cast concrete, i.e. the EPS melting might not affect overall floor integrity. I suspect had I looked into these in more detail 8 months ago, we might have made a different choice, but we are on course with the hollowcore now.

 

 

[Temp]

We have a beam and block first floor that has two quite deep steel UBs to reduce the span of the concrete beams. The B&B floor rests on the lower flange just like your hollow core. The tops of the UB project above the top of the blocks. These were hidden in the insulation layer before adding UFH in screed on top. 

[scottishjohn]

1 hour ago, kxi said:

Thanks all of the comments. Thinking about it today, I think there's flaw that in our case means we can't use the structural topping to lay the UFH pipe.

 

The planks are laid on the bottom flange of asymmetric steel beams in a 'slim floor' style, in order to save height. e.g.

(based on shallow-floor designs such as https://www.steelconstruction.info/Floor_systems#Shallow_floors)

 

Since the structural topping doesn't in our case go over the top of the steel beams, the UFH pipes can't go through the beams (without complexity).

 

However, if anyone is ever interested in UFH pipes in hollowcore topping, it does appear that it is (or at least was) tacitly supported by US and Canadian building codes:

http://www.healthyheating.com/Concrete-codes-radiant-heating/Concrete-codes-radiant-heating.htm#.XZpJr0ZKhhF

 

The middle one was what i was thinking of. 

 

@scottishjohn 

The ICF floor style is neat and something I would have looked into, but in our case this floor is over an agricultural-use ground floor, which could have vehicles, workshops, storage, etc in  and I am very concerned about the effects of a fire down there on the house above. Any EPS in the floor soffit I would expect to last hardly any time before melting. In the EKONECT and quad-deck examples it looks like the EPS in the floor doesn't provide any structural aspect, as that's all handled by the cast/pre-cast concrete, i.e. the EPS melting might not affect overall floor integrity. I suspect had I looked into these in more detail 8 months ago, we might have made a different choice, but we are on course with the hollowcore now.

 

 

correct

the eps in those systems is purly insulation and a former for the concrete -no structural value once concrete is poured.

 but whatever system you use you have to have an insulation layer between concrete and UFH -or you will be making a radiator out of the floor structure to heat down stairs workshop-very expensive to run 

 if worried about fire below then maybe you should be fitting sprinkler system what ever system you use simple to do and can run on mains watrer pressure 

[kxi]

@scottishjohn

Yes the plan is for 150mm of either phenolic or kingspan quadcore panels on the soffit, should give about 0.12U.

 

I had wondered about something like a mist system, but needs more investigation. As per 

it may be a really good alarm system(s) might be more effective. 

 

I did once live in a flat where a mattress was set alight in an abandoned flat below, and the first I noticed was the floor under my sunday morning feet starting to heat up. This early warning won't be available with 200mm of concrete.

[scottishjohn]

2 hours ago, kxi said:

@scottishjohn

Yes the plan is for 150mm of either phenolic or kingspan quadcore panels on the soffit, should give about 0.12U.

 

I had wondered about something like a mist system, but needs more investigation. As per 

it may be a really good alarm system(s) might be more effective. 

 

I did once live in a flat where a mattress was set alight in an abandoned flat below, and the first I noticed was the floor under my sunday morning feet starting to heat up. This early warning won't be available with 200mm of concrete.

I think that is a distortion --if you got a workshop with vehilces~+oil +fuel etc  a sprinkler system would be the best way to stop it getting out of control 

water damage  in a worshop!!!-that would be nothing as all surfaces will be hard ones 

and surely you would have both an alarm as well as sprinklers

Edited October 7, 2019 by scottishjohn

[Temp]

Is water is ok for petrol fires?

[scottishjohn]

3 minutes ago, Temp said:

Is water is ok for petrol fires?

no -  AAA foam is preferred  method as in aircraft fire engines  but the sprinkler system should stop it getting to a point where petrol is running everywhere 

sprinkler systems is what they use for underground car parks 

[kxi]

Also worth considering that in the not too distant future there might be some large EV batteries in there periodically. Who knows what chemistry these might have in future, but no doubt there will be guidance / regulations on fire safety relating to EV parking. I suspect for now we'd have a 'no EV under there' rule until the world understands the risks better.

[scottishjohn]

3 hours ago, kxi said:

Also worth considering that in the not too distant future there might be some large EV batteries in there periodically. Who knows what chemistry these might have in future, but no doubt there will be guidance / regulations on fire safety relating to EV parking. I suspect for now we'd have a 'no EV under there' rule until the world understands the risks better.

your living space above will need to be fired proofed and vapour proof from the garage /workshop below anyway even now -so don,t see nay great problem 

 same as connected garages  now need to have a lower floor level to stop flameable fluid /fumes etc entering the house by any linked door 

Edited October 8, 2019 by scottishjohn