Cap pour over esisting slab?

Unknown

What's the easiest way to attach PAP to a concrete slab?

The contractor poured the concrete and now the owners want a radiant floor. High heat loss due to lots of glass and I'll need to space my tubing 9" O.C. Lots of fastening. I remember in the early days, I had used duct tape to keep the tubing in place with poor results. I've seen rail systems but I'm not sure who makes them?

The tubing manufacturer (Wirsbo) reccomends 3/4" cover over their tubing for this application. Can it be any less? Or, will a thin cover create noticable striping. Tile is going to be used as their floor covering. The existing slab is 6-8" thick with 2" of full coverage insulation. Probably going to be a really slowly responding room.

Also, what can I do to prevent cracking of the new concrete overpour?

Gary

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Brian

Overpour

I've done a couple of jobs like that.First I put down bubble foil and taped the seams.Then I put down Heatlink track (I prefer it to the Wirsbo)and taped it to the foil with Tuck Tape, it's the red tape thats used on vapour barrier.You could also use wire mesh.Both overpours were down with gypcrete.Do an internet search for Maxxon and find a dealer in your area.

Good Luck
Brian

harvey

heat link

We just finished a basementthin-slab.. It was the first time we used HeatLink tracks. They woked great. Because the slab was 8' below grade we didn't put down insulation. We used liquid nails to secure the track, NO DRILLING After an hour we snapped in the tube.

hr

Once upon a time

I did a gyp over pour with Onix tube for a Heatway employee. We used nothinb but construction adhesive. That's one thing about rubber. It lies flat like an extension cord. It was an 1-1/2" gyp pour.

As far as thickness of pour, it depends on what you are pouring!

Concrete needs to be 3 times the aggreate size over the tube. So if you go with a pea gravel redi mix, you need 3/4" over the tube.

I think gyp could be thinner, but check with the gyp installers.

JLC this month has an article on polymer concrete mixes. Claims it can be site mixed and poured to 1/4" sounds like a "super gyp" type of product.

I would think the tracks or condiut clips would work.

Hitachi makes a concrete nail gun. It runs on compressed air like a regular nail gun. Might be able to rent one.

PAP should be fairly easy to keep in place with even 3 foot spacing of the tracks or clips.

hot rod

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Dan Peel

3/8 Kitec

This house had a circa 1950 copper L radiant floor leaking at it's buried returns. The replacement consists of 3/8 kitec with site mixed gypcrete between. Tiles are thinset directly above - tube spacing 6" OC. Enjoy.....Dan

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Unknown

Hmmmmmmmm? Still confused what to do.

Brian, Why did you use a bubble/foil product under the cap pour? The contractor and I are concerned about having a not so firm floor. Tile contractor won't warranty his work over anything he's afraid will have ANY movement. What if they go and drop in a Grand Piano? Did the overpour show any signs of cracking? Jury is still out on the true value of reflective products under concrete (far as I know.)

Dan, On that job you have in the picture, it looks like the gypsum/concrete comes right to the top of the Kitec. I'm wondering if it's such a good idea to have the top of the tube in dirrect contact with the tile? How evenly is the heat dispursed? Seems like it would work fine other than the striping effect. Did you hire a gypcrete contractor? Or, mix it yourself onsite? Can you buy gyp/crete and do it yourself. I thought this stuff was onely to be used where weight was an issue. Seems a bit expensive and not as strong as concrete. Will it expand and contract at the same rate as the concrete below? What's your reason for using gyp rather than portland base cement other than the aggrigate size as hr pointed out? Will it last?

HR, Do you think construction adheasive would work holding down PAP without tracks? Pl 200 or something like it? I'm going to experiment with a glue gun tomorrow. Not sure if it will hold on concrete surface. Why the 3x aggragate size over tube rule? Just curious. Seems to me that a 1x aggrigate would be fine.

What about perimiter insulation? I'm not sure how to impliment it into such a thin pour. 1 1/2" max. of concrete mixed onsite by the contractor is what we're planning to do so far (unless I can come up with something better.) Downward losses will be slowed down once the heat reaches the 2" foam/board under the current slab. (Slow responding flywheel effect) What about losses to the side of the new pour? Any suggestions?

Gary

PS Thank you guys for all of your advice. I really do appreciate it.

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Brian

Gary

I agree that the jury is still out on bubble foil.The important thing is that it will provide a thermal break between the existing slab and the overpour.There's no use heating the slab and you will get a quicker response time when heating the room.The reason for the gypcrete is it is usually easier to get to the basement than concrete and easier to level.If you prefer to use concrete instead of concrete instead of gypcrete then go right ahead.Make sure it is use use a 3/8" aggregate and a fibre additive.

Good Luck
Brian

Earthfire

stone in thin pour

Why is everybody hung up on putting stone in a 1 1/2" overpour? Traditionally, mudbed for tile has run about 1 1/2" thick and was a portland cement and sand mixture. Wall mud has a little lime added to improve stickiness in vertical situations, and can be applied a little thinner. Check out some of JLC articles on wetbed tile. I've had the pleasure of tearing out old wetbed installions, some over a hundred years old, and there has never been anything easy about it. For reinforcement we use galvanized chicken wire or other similar sized agricultural wire on top of the tubing. (Expanded stucco cloth is too tight to work properly in a thin bed.) This puts the wire in the middle of the bed where it belongs. There is no appreciable difference in the weight of cement bed with or without stone, but is one heck of a lot easier to work with.

hr

How easy

do you want this to be?

I ,too, would like to see how well the adhesive works on PAP. Yes a clean floor would be important for glue "stick." I imagine you would still have to clip down the loop ends. The ability to stay down would depend on how roughly you install the whatever concrete product you chose. Kitec offers straight lengths of PAP, or copper would stay down with little encouragement, if splices don't bother you.

3 times the aggreate is what the director of the Redi Mix Concrete Association recommended at ther RPA seminar a few years ago. It's an ACI standard spec designed more for rebar application I believe, but would apply to pex for the same reasons?

The strength of concrete is in the aggreate. The smaller it is, the weaker the "package" The only reason to pea gravel a mix if for thin pours like this. Concrete wouldn't normally be mixed with this small aggreate. 1-1/2" aggreate seems to be the norm around here.

He also suggested beefing up the fiber mix for thin pours. Go with 3 lbs. per yard instaead of 1-1/2. That ought to provide a nice fuzzy finish for you! The concrete finishers will HATE that mix Fiber mixes are tough to get a nice finish on. Power trowels help, as they can burn off the fibers on the last go around. A small torch, the next day works also, to lose the "fur". Time consuming and back breaking work.

Yes the edge insulation would be important, and a challange. Do your best. With foam under the first slab, I'd be tempted to not foam or bubble between such a thin pour. It will cost ramp up and down time, however.

Or you could remove the old slab and replace it with tried and true methods. We need more pioneers, like you, however.

hot rod

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Unknown

Brian, Thermal break

I agree the bubble gap is probably going to speed up response time a bit. Better than nothing. But, I'm wondering if it's worth the effort and money. This combined with the tile contractor's statement that he won't warranty his work over this type of application or what I had also suggested = (Warmboard). I've also some reservations about cracking. Does the fiber additive prevent cracking? The GC will be mixing the concrete onsite and he's handeling that end. Should I request some special instructions when he gets and installs the cap materials?

Concrete VS Gypsum based pour? Hmmmmm?

Gary

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Brian

Gary

Concrete will be cheaper than gypcrete.Warmboard will be more expensive.How big an area are you doing?Has The contractor done this sort of thing before?There will be cracking but the the amount will be determined by the quality of concrete AND the person doing the overpour.If you are not comfortable with those factors then maybe the Warmboard will be the way to go.

Good Luck
Brian

jp_2

tubing to concrete

dan, how did you attach the tubing to the concrete?

also, are you not worried about heat expanding tubing cracking tile? I would worry about this, I let the water temp run away in 1 1/4" gypcrete and had some hair line cracks.
did the project used isolation membrane?

Unknown

Brian, hr,

The area is a nearly 500 Sq/Ft addition.The contractor has never poured over tubing before.

What shall I request the contractor to provide for the cap? More fiber, smaller aggrigate? He's planning on mixing concrete in a portable mixer and "souping it up." He says he'll use a bonding material sprayed onto the existing slab. I'm leaning away from a dry system at this point. Is there a place to go to show the contractor what I need to expect of him?

Any suggestions as to how to address the perimiter losses? I'm thinking it's too small of a profile.

Should I feed a constipated radiant floor more fiber;-)

Gary

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Brian

Mixture

I think at this stage you want to talk to the local concrete supplier or installer.The last thing you want is someone who has know experience with this type of pour."Souping things up "sounds to me that something else might be sacrificed.If you start making suggestions on how he can compensate to correct the situation and it goes wrong then it's on your head.I doubt you want that.

Good Luck
Brian

Dan Peel

The products

We used PAP 3/8" (Kitec) held down with 3/16 X 7/8 drive nails about 3ft apart using 1/2" copper clips. The expansion rate is only 10% that of PEX.

The original 54 year old slab had no surface cracking so, no, I don't expect any movement or crack migration. The gyp should act as a filler only - like the middle of an Oreo cookie.

I've used this several times before with good success, my preferred filler is a high polymer thinset. Hair line cracking of the substraight won't show - these are a very solid tile.

With low quality or brittle tile who knows?
Enjoy.....Dan

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Earthfire

use

The tile installer. Have the tile man install a mudbed for his tile.If he says he can't warranty that find a tile man that knows what he is doing . Also, Juicing up a concrete agregate mix will do nothing but cause mud seperation, shrinkage and cracking that no amount of fiber can compensate for.

ALH_3

Attaching tube to concrete

You might try using a Hilti nail gun and short nails with approx 1"x3" pieces of sheet metal to hold 6"x6" wire mesh to the concrete. Lay the straps of sheet metal over the bars of the mesh and shoot one nail on either side. Get the mesh panels and not the rolls......the rolls are impossible to lay flat. Then you can tie the tube as you would normally for a slab. Overall thickness with 1/2" pex is <1".

Unknown

I've decided to use Wirsbo's RAILS

Hard to find. Not too many being sold around here.
I'll show you all how it comes out. Pl 400 and glue gun wouldn't hold the PAP (Moltocor™) down:-
( Rails are onely $4.00 each for six feet.. Can't beat that compared to drilling a hole for each run. I'll fasten the rails on 3 points.

Thanks one and all.

*To catch up with me in real time, use AOL's Instant Messanger. My user name is: Radiantfloors
Add me to your buddy list. I've got a bunch of Wallies on my list.

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Weezbo

oki use acrylic adhesive in the mix. if you shoot mortar or gypcrete no matter it both takes forever to dry both shrink .stay off it a day or two strike it flat with a bullfloat and fresno. I am looking for a product maybe you can help me. it is a blue inter locking sheet board that has lego lock in it and you just snap it together place your rehau wirsbo or stadler pipe in it.pour the gypcrete out strike it flat go home callit good. any help? what is this stuff called?
it isnt quick track or anything like it. cuts with a sheet rock knife ....man id like to get some for my first spring start this year>!

Brian

Gary

Good Luck
Look foward to seeing the pictures

Brian