How soon after the pour?

Tomek

How soon after the pour can i fill the system and start circulating hot water?
1-1/2" Thermal Mass over plywood subfloor, 1/2" PEX mostly 6" O/C, boiler NTI
some say you have to wait until completely cured ~2% moisture, others say as soon as 24 hours latter to help ThermaMass to dry?
What is your experience?

Tomek

How soon after the pour?

How soon after the pour can i fill the system and start circulating hot water?
1-1/2" Thermal Mass over plywood subfloor, 1/2" PEX mostly 6" O/C, boiler NTI
some say you have to wait until completely cured ~2% moisture, others say as soon as 24 hours latter to help ThermaMass to dry?
What is your experience?

Mark Eatherton1

Gypcrete

wants heat IMMEDIATELY after its been poured. Not sure if the same applies to light weight concrete tho...

ME

Matt J.

Mark

we just completed about 4,000sgft house of 1/2 pex with inch an half gypcrete over it and I was told by the installer that I was not to turn on the system till at least monday. They poured it in two lifts, first half on thurs and the rest today. He said that they have had problem with there floors cracking if it was turned on to soon? He said that even at low temps that it pulled to much moisture out of the slab to soon. He even had the GC shut off the tempory force air furnace on this floor till mon. Basement in floor is on and heating. I'm just wandering if this it right or not? So I did what he said, but he wouldn't give a diffient answer until I said Monday? then he said that that would be fine. Not saying that your wrong but its got me wondering now if he knows what he's talking about? This company does alot of gypcrete jobs. Also I have a guestion about the moisture barrier they used? Its like a black vinyl with a type of black plastic webing over the top of it. I this what the rest of of you have encountered. thank matt j

Tomek

> we just completed about 4,000sgft house of 1/2

> pex with inch an half gypcrete over it and I was

> told by the installer that I was not to turn on

> the system till at least monday. They poured it

> in two lifts, first half on thurs and the rest

> today. He said that they have had problem with

> there floors cracking if it was turned on to

> soon? He said that even at low temps that it

> pulled to much moisture out of the slab to soon.

> He even had the GC shut off the tempory force air

> furnace on this floor till mon. Basement in floor

> is on and heating. I'm just wandering if this it

> right or not? So I did what he said, but he

> wouldn't give a diffient answer until I said

> Monday? then he said that that would be fine. Not

> saying that your wrong but its got me wondering

> now if he knows what he's talking about? This

> company does alot of gypcrete jobs. Also I have a

> guestion about the moisture barrier they used?

> Its like a black vinyl with a type of black

> plastic webing over the top of it. I this what

> the rest of of you have encountered. thank matt

> j



mine was abit smaller, 2,5K SQF, everybody I talked to confirms that initial drying should be in room temp without heat through piping. I am going to wait. I think that the previus guy meant heated space when he wrote "immidiatly heat", not heat in PEX piping

Mark Eatherton1

Could be...

a difference in where we're operating. I've been dealing with my gypcrete dealer for about 10 years here in the Denver area, and crackings never been a real big issue.

What does your gyp dealer think about allowing the gypcrete to freeze? Mine sez if you do, your warranty is void...

I've poured gyp in buildings that were BELOW freezing (10 degrees F) and the gyp actualy generates its own heat initially, but we started pouring heat to it immediately after is was poured.

You'll find differences in opinions in just about anything you do. I'm just going off of what my "gypcrete expert" has told me to do.

Your mileage may vary...:-)

What part of the country are you pouring in?

ME

Mark Eatherton1

Again...

I was told by my gypcrete dealer that the faster the moisture leaves the pour, the harder it sets up. If the moisture lingers too long, the surface stays soft and powders easily.

I do not profess to be a gypcrete expert. I'm only relaying what my gypcrete dealer tells me, and HE'S the expert.

But bear in mind that what I'm saying applies to a gypcrete type of material. If you're pouring light weight concrete, all bets are off...


ME

Weezbo

tomek ,...

cze*~/:) usually i wait the 28 days...in winter time or summer...last summer when it was 104 outside i was called to make the boiler Heat the slabs make an end run around the tekmar and boot the heat to it after 10 days...i had never and i have been doing this a While..never done this previously and was highly tweeked over it as i am a low water constant recirc or variable speed injection kinda guy well i did it and rolled 110 to it wahich satisfied the GC my buddy..this year i may be asked to do this again...this year our gypcrete has a new formula that is supposed to make it like snap set of sorts...good for the go in three days....

hr

Wouldn't it depend

on the temperature you are pouring in. We have done gyp pours in the dead of the winter and had the system running as we poured.

We did a large condo project in Deer Valley, Utah that started construction in the fall. We pumped gyp all winter long. The biggest hassle was getting the pumper started in the cold and keeping the water hoses from freezing as we pumped. Glad those days are over

Venting the moisture from the rooms or building is, by far, the biggest issue with gyp pours. You need to get the moisture out before the insulation or sheetrock absords it!

I would call the manufacture of the product or go to their website, they should know.

hot rod

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Troy_3

Gypsum concete

Wants to be maintained above 50 deg. till completely cured. then it doesnt matter if it gets cold. Do Not Let it freeze before it cures. Get the moisture out as soon as possible. You can't run the pex hot till the gyp gets it's initial cure because the pex grows so much it will come up through the pour. We heat the tubes before the pour. Shut the pex down during the pour and turn the heat back on low once the gyp gets hard enough to walk on. Then we turn the temp. in the tubes up the next day and get the moisture out of the bldg. as quickly as possible.

Troy_3

That's what we do

However you want to follow whom ever is guarenteeing the work. Just don't misunderstand what you are being told. No applicator should tell you to leave all heat off if the gypsum concrete will get cold. I'm shocked that they poured the two applications on two different days. Is that right? Who is the gypsum manufacturer? What did the bags say on them? Name?

Matt J.

Mark

I'm in lincoln ne. We did not totally shut off the heat in the house, the temp from the basement easily kept the house over 60 degrees. I just did what the GC said and the gypcrete man wanted, this company has many years of service in the community though there this towns only choice? They also do concrete work and I must say there are other concrete companies that do much better work then this company. They told me that it does generate its own heat for a time but they also told me that they did not want it to freeze. Troy I no idea why they did this thin of a pour with two lifts? They have done other jobs that I have been on in one lift, the only time that they typically do lifts are one that require a much deeper pour.

S Davis

Gyp

I have been told that a three day cure before firing the boiler system is recommended and if there is a chance of freezing bring in temp heaters, this from the Gyp company I have been working with for 12 years and have never had a problem.


S Davis

Apex Radiant Heating

Weezbo

my favorite tool is a WH and it cant putmore than 16000btus

into the slab if it wanted to:) so i usually roll it on the thick garage floor and lash up a boiler of sorts to a huge unit heater and place it in front of the supply and returns(ROUGH-in ductwork) of the HRV to distribute FA gently throughout the system and home, crack the winows every day and get the moisture out, prior to actually rolling heated water to the gypcrete...even then it is drawing off the thermal mass of the garage slab and the water heater for days ...at low temp...just to disperse a few friendly BTU's. i have a temp gauge on whats going out and use my laser gun to check temps daily of floors tubing and surfaces..... they hairline cracks are then clearly a process that occurs from consistency of the gypcrete and any setteling due to weight ,or ocassionaly the cracks follow a sheet of plywood,.....i hope this is a good example to follow and have no problem with any aspect of the procedure to date.*~/:)

Tomek

how soon after the pour?

Thank you everyone, for sharing your experiences.
I was trying to workout a happy medium for our project,

and against the information from gyproc installer (wait until completely cured 2 weeks) I put low heat through PEX pipes on the 3rd day after the pour was completed. At some time after (4-5 hours) I noticed hair thin cracks in one section of the slab, along the lines of the pipes. I switched the heat off. I think gyprock was not cured enough, and expending pipes lifted the slab a bit.

The heating in the basement has been working for weeks, and I use electrical heaters to heat the house above 15C, so I will wait for 2 weeks for gyproc to cure completely before heating it up again. I am opening the windows a bit during the day and leaving exhaust fans on for the night. Oh, I forgot to say, we are in Toronto, Ontario, Canada so nights are below freezing.

Again thank all for good advice