concrete floor questions,stones,insulation,etc.

[timberwolf]

need to understand more... some floor guys say don't need 4in. of stone under concrete/ others won't pour without it ?? want to insulate under floor because puting heating tubing an some say just 2 feet around edges...others say whole floor needs ins. any concrete guy's out there ?? whats your opp. ?? thanks.

 

[GSSFC]

If you are putting radiant tubing in, you need insulation under the slab to prevent downward heat loss.

I will ONLY use stone under concrete, but there are a lot of homes out there with sand and it seems to be ok. I use stone, it is a relatively inexpensive upgrade, and you only get one shot at doing it!

Tim

 

[menz300]

I agree with the stone. Also compact it good. Also make sure your slab is proper thickness as some might try to cheat you a bit. I am also a big believer in insulation if you are going with radiant flooring. For the few bucks it costs do it right. Seeing you are doing radiant heat can tell you are more than likely not skimping so do insulation and stone. Can verify that in floor heat is a beautiful thing and you will love it.....

 

[rlme36]

If you are doing radiant heat in the floor and the building isn't used all the time you'll really appreciate the entire slab being insulated. It will decrease the recovery time of the slab. I have 6" of stone on top of compacted soil base with 6" slab thickness with a 10" thick pad area for the lift location. It depends on what you plan to do with the space.

At the moment I am having a heck of a time keeping my system pressurized due to the faulty schrader valve that was sent, too a while to track that down thanks to soapy water.

 

[timberwolf]

thanks, for the replys ! still learning. so... insulate whole slab..? some guys localy say, just 2ft. around edges. i'm in south jersey, just want to make the right choices the first time around ! going to be a garage/workshop an snowmobile/atv's an work on the pickup type of place....thanks.

 

[tcianci]

The purpose of the stone is to provide a "well drained" area under your slab so that it won't heave in frost conditions. It functions in 2 ways. Frist, water expands as it freezes as we all know. When it freezes in a densly packed, poor draining situation, it will make the the area crown up, known as a frost heave. What you are trying to accomplish is to have an underlayment that will be load bearing and dry. Since the stone, no matter how tightly compressed or weighted, still has voids between the individual stones, there is space for the frozen moisture, if present, to expand into. It works beautifully. If you have no frost related issues, you can pour on just about any type of soil or stone. Secondly, if you install the stone such that it can act as a "condiut", large quantities of water can pass under the slab so long as you provide someplace for it to go. Insulation is a must for an in-floor heating system.

 

[Jeepskate]

I'm in this stage of my building planning right now and have been digesting a good bit of info over the past few weeks. Here's what I've gathered:
1) Vertical insulation (up the side of the slab, is a must do)
2) On a smaller building, you can go either way underneath the slab...insulate it or don't. Without the insulation, you'll get heat penetration down about 3-4 feet, however that penetration also serves as heat storage and can help you coast through early Spring and late Fall with little to no use of your heating system...downside is that the system is slower to respond to cranking up the t-stat.
3) On a larger building where you have the space to do it, insulate the first 4 feet at 2" thick and the next 4 feet at 1" thick and leave the middle open for heat storage (or go ahead and insulate the whole thing if you don't want the storage).

You might find it helpful to read through the materials at www.radiantec.com

I'm by no means an authority on any of this and haven't even broken ground yet.