Radiant heating/concrete floor question

Elizavet

Hi

Apologies for not being familiar with the technical jargon, but here goes.

We will be installing radiant heating in our new home. The finished floor will be the concrete surface (i.e. no tile or wood). However, we live in Thessaloniki, Greece, and are having difficulty lining up the people who know how to work with both radiant heating and finished concrete floors. The person who will be installing the radiant heating system uses a German company called "Rehau" - and Rehau says that we must use a sand concrete mix, rather than, say, pea gravel. From what we understand, this is to provide both a better thermodynamic result and to avoid puncturing the radiant tubing.

We've finally found someone who has trained in Italy and has the diamond sanders for sanding concrete. However, both he, the person who is pouring the cement and our general contractor tell us that a sand-based cement can't be polished because it will make the cement floor rough. I guess sand can't, uh, be "sanded." This guy tells us that we need to use pea gravel.

It's been suggested that we pour the cement floor in two stages - sand first to cover the heating tubes, then following with a pea gravel finish - but our contractor tells us this two-part approach is less than ideal.

Web searches that I've done do seem to indicate that pea gravel is fine (perhaps even standard?) when pouring cement for underfloor heating - but I could be misreading things because of my lack of technical knowledge. This is especially frustrating because from what I understand, a bare, stained concrete floor is the ideal partner for radiant heating.

So. Is the German company being overly picky by insisting on sand only, or can we feel safe in going with pea gravel?

Thanks in advance for any information - we're a bit confused about how we're supposed to make this floor work!

Carlow52

All the way from Thessaloniki, how about that:)

the 2 part approach is only less than ideal as it is a little more work.

If it is done while the sand/cement is still fresh/uncured it will work fine, I presume the screed is non structural.

even if done in two different pours as long as the pea gravel layer is say 2 " in depth then it should not be an issue.

Have u any idea what the mix is in the pea gravel application: could the peas not be tamped into the sand cement after the s+c is poured

Thessaloniki" I must reach for my Uzi, or is it Ouzo, i forget:D

Elizavet

Hi Carlow52

Thanks for your response - appreciate it.

Good to know that the 2-part solution doesn't affect structural integrity. I know we have to keep the floor a certain depth, however, so I'm not sure if we have a 2" margin. I'll have to find that out. Certainly it would drive the cost up, I would think.

Interesting idea about tamping the peas into the sand cement...I'll bring that up with our contractor.

We spoke directly with the Rehau this morning. Turns out they had a client who used the radiant heat with the sand-cement mix on an island home and the guy had no problem sanding it for his final floor. Of course, we have no idea what the result actually looks like, but they said it was fine and their customer was happy with it. Apparently, the sand they recommend is fairly coarse, but I guess you can "sand sand." They also told us that we could use pea gravel with out any problem, but they won't stand by the result.

Jeez - you would think this is new technology or something! Our heat source is geothermal, so we want this all to tie together as well as possible, while keeping the total cost under control and the aesthetics lookin' good.

Reach for the ouzo...an uzi might get you into trouble ;D Ouzo sure tastes a lot better, too


E

Oh, by the way (I'm learning as I go, here) - "screed" refers to the cement slab, or to the tool that levels the poured cement? I googled it, but didn't find a clear answer...or at least, one that I could make sense of!

muffler

"Screed" or finished floor as some call it is a layer of cement usually 70 - 100mm deep which is poured on top of your concrete sub floor.

Elizavet

Hi Muffler

Thanks for the definition. So as I understand it, the pipes (tubes?) for radiant heating will be within the layer of screed - which we're hoping that, once polished and stained, will be our finished floor.

I'm learning, I'm learning....


E

Carlow52

Elizavet wrote: »

Hi Carlow52

Thanks for your response - appreciate it.

Good to know that the 2-part solution doesn't affect structural integrity. I know we have to keep the floor a certain depth, however, so I'm not sure if we have a 2" margin. I'll have to find that out. Certainly it would drive the cost up, I would think.

Interesting idea about tamping the peas into the sand cement...I'll bring that up with our contractor.

We spoke directly with the Rehau this morning. Turns out they had a client who used the radiant heat with the sand-cement mix on an island home and the guy had no problem sanding it for his final floor. Of course, we have no idea what the result actually looks like, but they said it was fine and their customer was happy with it. Apparently, the sand they recommend is fairly coarse, but I guess you can "sand sand." They also told us that we could use pea gravel with out any problem, but they won't stand by the result.

Jeez - you would think this is new technology or something! Our heat source is geothermal, so we want this all to tie together as well as possible, while keeping the total cost under control and the aesthetics lookin' good.

Reach for the ouzo...an uzi might get you into trouble ;D Ouzo sure tastes a lot better, too


E

Oh, by the way (I'm learning as I go, here) - "screed" refers to the cement slab, or to the tool that levels the poured cement? I googled it, but didn't find a clear answer...or at least, one that I could make sense of!

When i wrote

If it is done while the sand/cement is still fresh/uncured it will work fine, I presume the screed is non structural.

I was highlighting the fact that I am assuming that the screed is NON structural and therefore could be done in 2 parts as it has no requirement to carry loading.

I doubt it is structural but just make sure. I think from your reply that you are clear but just in case.

Re screed, Muffler has answered the question, the other meaning it has here at the moment is that most people dont have a screed:)
Keep well

Elizavet

Hi again, Carlow

Nope, the screed is non structural. As with most construction in Greece, our house is made almost entirely of cement, of course including the subfloor. If we weren't using radiant heating, theoretically, we could tile over the floor as-is and we'd be good to go. The screed is just for encasing the radiant heating and for giving us - hopefully - our finished floor.

Thanks again for your help. If you can think of anything else that might be relevant, I'd appreciate your two cents!

E