Concrete Slab and Radiant Heat

[Steve_M]

I am getting ready to poor a floor in a 30 X 50 pole barn and have a few questions.  I intend to do as much of the prep work as I can and get a little help with the concrete.

So far I have insulaleted around the inside of the building to a depth of 2 ft in order to stop the heat loss out of the side of the slab and I have added fill and compacted the base.

My idea is to divide the floor into 3 sections---7 x 50 on each side with a 16 x 50 down the middle.  Pour the sides first then pour the center later.  This will allow me to use 4 runs of PEX 300' each.  Each section will have vapor barrier, insulation, and rebar on 18" centers with the Pex tied to it.

Finally my questions:

1)  Do all three sections stay seperate or does the rebar need to connect all three?

2)  When the Pex crosses from one section to the next does it need extra protection at the joint?

3)  Do I need an expanision material between the concret at the joints or can I pour right up next to   the side of the first section?   

4)  Where should I bring the heat into the building?


Any help or sugestions will be appreciated.


Steve   

[OneWithWood]

Steve,

Check out this thread.  It may have some info you can use.
https://forestryforum.com/board/index.php?topic=9529.0

[slowzuki]

1) I'm connecting all the slabs in mine so they stay keyed together without lift at cracks.

2) At my sawcuts I'm using 1/2" pipe insulation on the tubing to keep it from damage as the slab shrinks.  I Don't think it needs it but I want to make sure it is ok.

3) No expansion needed, concrete shrinks as it cures. About 1/2" per 60 ft or so?

4) I don't have an answer.  We are heating from wood boiler inside the building but all the mechanicals are coming through one area under a stair.

Finally my questions:

1)  Do all three sections stay seperate or does the rebar need to connect all three?

2)  When the Pex crosses from one section to the next does it need extra protection at the joint?

3)  Do I need an expanision material between the concret at the joints or can I pour right up next to   the side of the first section?   

4)  Where should I bring the heat into the building?
Steve   

[florida]

Rebar on 18" centers isn't going to do much for you except make you sweat installing it. If you're pouring a 4" slab it won't do anything at all since properly it will be too close to the bottom of the slab to add strength. Reinforcing material should be in the bottom 1/3 of the slab to work. By the time you place 1/2" rebar you will only have 1" of concrete under it. You'd be better off using 6"  on center steel reinforcing wire if you fell like you really need it. Better yet have your concrete supplier add fiberglass to the wet mix and forget the steel.

I would use keyways on the adjoining edges rather than rebar. That way the slabs will move together and oyu won't have to worry about your PEX.

[Don_Papenburg]

PEX crossing from one slab to the next should be covered with a pipe one foot into the slabs . (Radiantec)   I would use steel but the PEX should be closer than 18"   I went 12 on my basement but any thing above grade I would look at going 6 "  That way the heat does not have to be so high and the heat striping will not be noticable.
If you want to go 18 " put the PEX in the sand fill under the slab and over the insulation.
Key the slabs and run the rebar into the next slab at least by one foot
No expantion needed inside.

[Daren]

Steve
Shoot me an e-mail, I am a 3rd generation plumbing heating contractor with 20 years personal experience, specializing in hydronic (hot water) heat. I have installed hundreds of miles of PEX, there are certain ways to lay the tubing. You want the supplies of one loop next to the returns of the one next to it to maximize heat gain. Your are the right track by insulating the perimeter, there is a certain way to lay that tubing as well (and around any doors). I am not going in to the whole system in this post. Contact me and I will provide you with a schematic of tubing layout and a few pointers on the rest. I just engineered and installed a 75X65 shop with 16' ceilings with a 24x16 office on a seperate thermostat , 15 loops, 5 pumps,  2 manifolds... One little boiler will run you out at -0. I don't know alot about wood and sawing... that is why I visit this board, I am sorry I can't help much with the cold lapping of your slabs either (that needs special attention with the tubing, they make a inexpensive solution). Heating is no sweat ,pun intended.
Daren

[Frank_Pender]

Not to take the thread too far afield but, Daren, what would you charge aside fromthe fair to come out here and lay out a system in a new building I may well build this Summer? ;D ;D ;D ;D

[Daren]

Frank
I have never been to Oregon, seems like pretty country. If you get far enough along and need some advice, give me a shout. The laying of the tubing a monkey can do and it will work, but to make it heat well with the lowest fuel costs just takes a little know how. Know how is an easily transferable thing. Heck, I am knowing how to saw,dry,sell from reading this board.

[Kirk_Allen]

Got to love this place 8) 8)

Daren, I am building a 40 x 112 shop this summer and and want the radient heat flooring.  I sure would appreciate any and all input you can give me on the best way to lay the tubing, where to get it etc.  I know nothing about it other than what I have read on line, and that is limited. 

The building will be supported by 6x6 posts on 8 foot centers, which are sitting on 18" pillars that are 30" deep.  The slab will be poured around those pillars. 

Thanks

[UNCLEBUCK]

Hello Steve M , I asked my dad who is a retired concrete man , last job he did was the metrodome  stadium in minneapolis . He say control joint needed every 30 feet maximum on  your 50 foot run  and rebar need to be cut 6 inches past that control joint and tied into the remaining and use whistles or grease where the the rebars meet there so the slab can move . Same for your inside pour , Its the 50 foot length that needs the control joint somewhere .The 30 foot way youre good to go as that can be continuous rebar . You have a good idea of keeping your pex runs all the same length or else it will be hard on your pump . But make sure you mark your spots on your form boards where you will cut in your expansion joints and before you pour you can look and see your splices in the rebar and you should be good to go . I poured a 28x50 one year ago today and did that pex and insulation thing, sure feels good on the toes , if you click on my photo gallery I have a picture of my little hydro-shark mini boiler that just plays with the slab at 30 below zero . I will dig up a good pic of the pex before I poured and post it here for you.  They make a sleeve that can be placed over your pex tubing where you have your control joint and also sleeves where your pex comes out of the slab .

[UNCLEBUCK]

[UNCLEBUCK]

[UNCLEBUCK]

Well ok da pics made it , see where the pex tubes come out and I have them mounted to a temporary board which is now where it all hangs on the wall of my utility/laundry room . Come in anywhere I guess but it sounds like thats Darens department . I just know my dad was a 40 year concrete man and when he say control joint on the 50 foot span somewhere like 25 but no more than 30 he means it. Its hard to get them old farts to talk sometimes. Good luck and take alot of pics !  ;D

[UNCLEBUCK]

Oh one last note is I put the 2 inch blue board on the sides afterwards and I was going to put it also under the footing but my dad thumped me on the head about that idea . I like the way you said you allready have the insulation installed at the sides . It took 11 gallons total to fill all the tubing and have was anti-freeze boiler juice . 30 below zero I was walking around in my socks and even turned the heat off a few days at a time and maybe dropped 10 degrees . Ok I done now !

[Daren]

Looks like UncleBuck figured it out just looking at the picks. They make a product called Insultarp, that replaces that blue board, man is it easy to work with, you just roll it out. It costs more, but it is the only way to go. Kirk, I can do the same as I mentioned to Steve. Just shoot me an e-mail with the basic layout (overhead door placement that kind of stuff), I can give some pointers. 42x112, that is a few rolls. The install cost scares some people off, but in slab is the only way to go. I put heat in a guys tractor shed, he had a 30' wide overhead door. On a cold windy day you can open the door and pull a truck in, when you shut the door you haven't lost all you heat (cause it is in the slab, not just the air)

[Vermonter]

In case you don't have the link, www.radiantec.com is up here in Vermont.  I have used their tubing, manifolds, and mixing valves a number of times.  They are very helpful with their advice and design assistance.  They are really well set up for the "do-it-yourselfer".  Their materials are about a third the price of heatway etc.  I figured that even if the tubing didn't last as long, I could do it over again every 20 years.  They have systems that have been in place for many years.  They ship anywhere.  On the first job (1200 ft of tubing, 3 loops), I bought their tubing because I could make up my own manifolds (yes, I'm really cheap).  On the last 3, I've bought their manifolds, as a 2 loop system, with a plywood form box and pressure gauge for the pour was only a little over $125 delivered.  I pressurize the loops before I pour, let it sit overnight, and usually pour under pressure. 
I also recommend mesh.  If you use mesh above and below the pipe, it reduces the chance of a shovel cut in the pipe, and the pipe will never float up. The mesh on the bottom does little to strengthen the slab, so you don't have to be real exact with the overlap, in fact, I usually space it out a couple of feet apart which saves a couple of sheets.  I like the flat sections, as I don't have to wrestle with a roll.  I have also used worn out highway fencing for the bottom layer, just to fasten the pipe to.  I use new for the top layer.  The top layer will wind up at about 1.25" from the bottom of the slab.I use zip ties rather than wire ties, but remember to clip the excess off, as they always seem to surface when you are troweling.
I also recommend a pipe sleeve at the expansion joints.If you use mesh above and below the pipe, it reduces the chance of a shovel cut in the pipe, and the pipe will never float up. The mesh on the bottom does little to strengthen the slab, so you don't have to be real exact with the overlap, in fact, I usually space it out a couple of feet apart which saves a couple of sheets.  I like the flat sections, as I don't have to wrestle with a roll.  I have also used worn out highway fencing for the bottom layer, just to fasten the pipe to.  I use new for the top layer.  The top layer will wind up at about 1.25" from the bottom of the slab.  Before and during the pour, I try to walk on top of the pipe.  This keeps the mesh from bending, etc.
There is a product for the expansion joints, it looks like sawdust board soaked in roofing cement.  We have used everything from pine boards to vinyl cove base, to sawing the joints with a wetsaw, but I like the expansion joint material best.  I just nail it to the first slabs to make sure it doesn't float when you pour.
Hope that helps,

[Steve_M]

Thanks for the replies everyone----good info and good pictures .  Been distracted from the concrete project the last couple of days by sawing projects.  I think I would rather saw and let someone else take care of the shed project :-\------that would be to easy wouldn't it ???.  I do have more questions and I need to send some IM's, but it is too late now to think about it.  Thanks again.


Steve 

[Steve_M]

Finally got the floor poured this last weekend 8).  Anybody have any thoughts about how long I should wait before I start heating the floor?

Steve

[OneWithWood]

How long to wait is dependent on the mix you used, any additives and the weather.  Ideally you want the concrete to cure slowly so little strength is lost.  I would wait as long as feasible before heating the slab.

[BW_Williams]

I poured my garage slab in '95 or '96 with 825' of tubing in the floor and haven't heated it up yet :D  I bet it's through curing :D

[Vermonter]

7 days should produce 80% of rated strength.
I don't think the heat is that stressful, it would be a better choice to run some heat through it than to let it freeze.  Wiam gave me a good bit of advice the other day, he said to just install two ball valves rather than a mixing valve.  I've been adding a $100 adjustable mixing valve on the return, and he pointed out that you never change the setting.  I think I'm going to add a couple more thermometer taps in the next install.
Did you use radiantech tubing?

[mometal77]

i posted this on another thread..http://www.concretenetwork.com/concrete/radiantfloorheating/thermalmass.html

[OneWithWood]

I finally got around to uploading a pic for this thread.  Here is the REVISED plumbing for the water lines coming into the slab for the greenhouse.  My first two attempts had a few components missplaced, like the pump in the feed line after the bypass and mixing valve - did not work too well.
The correct set up for us was to relocate the pump to the return line ahead of the thermostatically controlled bypass.  The mixing valve is located in the feed line and draws cooler water from the return line as needed.
I hope this pic is helpful and saves someone from the mistakes I made.  I did get proficient at sweating copper!  :

[Vermonter]

Looks like you've got it....
I think I've posted this link before, but http://www.radiantec.com/
If you check out the SYSTEMS pull down menu, they have very helpful animated graphics for each of the circuits.

[maple flats]

OWW, is that a Taco pump? Looks like the motor is not horizontal. I worked for years using Taco pumps and ran into short life expectancy anytime the pump motor was vertical. These get their lubrication from the water and air pockets restrict complete lubrication, even with the motor down below the pump head. Check the paperwork that came with the pump and it will show this.. Just need to turn the motor 90 degrees and all will be fine, can pump up, down or left ore right as long as the motor axis is level.
Maple Flats