We are about to pour the garage and I am getting some hassle because I want it poured over poly so I don't have any moisture issues with epoxy floor paint. Just exactly how much longer does it take to cure over poly versus non-poly? Should I just skip the poly? BTW we get about 17" of rain and lows in the teens to highs in the upper 90's. Thanks.
Cement Curing Time Over Poly?
- Thread starter 04 Navi
- Start date
Don't skip the poly!
True, the slab will take longer to cure with poly underneath. This sounds like a contractor doesn't want to spend the time for the slab to cure enough to trowel.
For the best results, pour the slab on a moderate day with no rain in sight. You can get away with pouring on a colder day if you have some calcium added to the mix as it will speed the initial cure time and allow for troweling sooner. This is how my slab was poured. I poured it on a 35 degree day in November. Not the best conditions, but it worked out...and I laid 5mil poly down before the pour.
True, the slab will take longer to cure with poly underneath. This sounds like a contractor doesn't want to spend the time for the slab to cure enough to trowel.
For the best results, pour the slab on a moderate day with no rain in sight. You can get away with pouring on a colder day if you have some calcium added to the mix as it will speed the initial cure time and allow for troweling sooner. This is how my slab was poured. I poured it on a 35 degree day in November. Not the best conditions, but it worked out...and I laid 5mil poly down before the pour.
Ken Greene
Well-known member
al;so you can lace te poly under 3-4" of compacted sand then pour ontop of the sand. you still get your barrious and the maoisture in the concrete can go into the sand to help speed evaporation.
Dave Carney
Well-known member
Ken Greene said:
I read lately that this practice is no good and to be avoided....has to do with the water retention properties of sand.... in fact the consenus on poly seems to change by the minute........I also read that anything less then 10 mils won't last under concrete....i think I'm going to skip it.
JohnZ
Well-known member
Don't skip it - you'll wish later that you hadn't; no floor coating will last with moisture migrating through the slab! I have 10-mil poly and 5/8"-thick 4'x8' sheets of high-density closed-cell foam with heavy foil on both sides under my slab, had no problems pouring or finishing it. Let it cure for three months, then had the epoxy floor done. That was six years ago, and the epoxy floor still looks like it was poured yesterday.
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Dave Carney said:
I've heard the same about the sand.
I have not heard about the <10mil deal. The effectiveness of the vapor barrier has to do with the quality of the plastic. Granted, a 10 mil barrier will have less permeability than a 5 mil (like chemical makeup), but there is nothing that I've seen that says a quality 5 mil barrier made of virgin poly won't last in most instances.
Dave Carney
Well-known member
If you google this topic you can read until the end of time about the pro's and con's. Floor covering is not a deal breaker to me since this will be a working garage (welding, cutting, fabricating).
http://irc.nrc-cnrc.gc.ca/pubs/bpn/8_e.pdf
http://www.findarticles.com/p/articles/mi_m0NSX/is_11_50/ai_n15878161
http://www.askthebuilder.com/445_New_High_Performance_Vapor_Retarders.shtml
http://irc.nrc-cnrc.gc.ca/pubs/bpn/8_e.pdf
http://www.findarticles.com/p/articles/mi_m0NSX/is_11_50/ai_n15878161
http://www.askthebuilder.com/445_New_High_Performance_Vapor_Retarders.shtml
mike944
Well-known member
Thanks guys. We ended up not pouring due to rain. Hopefully this week. I had wanted the poly down before the gravel but I stepped out to run an errand and the truck came a day earlier and dumped in the garage, so it was them poly on top of the compacted mulch. It will work. Thanks again.
filthy_shovel
Well-known member
As a matter of fact, whatever you do, poly, no poly, cement always takes 28 days to cure.
filthy_shovel said:
True, but I think he was referring to the time it takes for the slab to initially cure so that the contractor can trowel the surface. If it takes longer to harden up, they have to sit around and wait before they can trowel. Contractors hate to wait around, like most people, as time = money.
What's the deal with the mulch??? 
They poured my slab when it was 45 outside. Put poly down on top of the fill sand, added wire, and then poured. 4 hrs later it was being power troweled. If it's cold enough to freeze, make sure they blanket the slab. Mine has been blanketed for the past 2 weeks to help cure and protect from the water freezing in the control cuts. At least until the builder gets it framed up.
They poured my slab when it was 45 outside. Put poly down on top of the fill sand, added wire, and then poured. 4 hrs later it was being power troweled. If it's cold enough to freeze, make sure they blanket the slab. Mine has been blanketed for the past 2 weeks to help cure and protect from the water freezing in the control cuts. At least until the builder gets it framed up.
Thanks. The mulch is a stone mulch of crushed rock. It is power vibrated and forms a very hard pervious surface. And yes I was talking about initial curing time, not overall. Thanks again. As freezing they are going to add some calcium to make it hotter and it will be blanketed. Hopefully it's going in today. I am 300 miles away today so it's tough to find out info. Thanks again.