Warming Concrete Floors

[Avadon]

Hey does anyone know how does one prevent underfloor pex heating from freezing and bursting? Do they put antifreeze in the lines? For example, what are the fail safes should your building heat fail and the floor heating be at a point where it is not circulating?

[Sask Mark]

Hey does anyone know how does one prevent underfloor pex heating from freezing and bursting? Do they put antifreeze in the lines? For example, what are the fail safes should your building heat fail and the floor heating be at a point where it is not circulating?

Glycol is used in the hydronic systems around here.

[Sask Mark]

 If you had even a small bit of ice you might not be able to get vehicles out and salting ramps is messy and throws the salt everywhere.

 

Salt is only effective a few degrees below freezing.  We get -30 C weather fairly routinely during the winter and salt does nothing to stop snow and ice buildup at those temperatures.  The hydronic heating combined with a herringbone finish to the concrete and a drainage trench at the bottom of the ramp are the common ways to battle the ice/snow.  

[Avadon]

Glycol is used in the hydronic systems around here.

 

is it impossible for that stuff to freeze?

[Jack Evers]

is it impossible for that stuff to freeze?

It's good to -40 in a 50-50 mix and then it won't swell and bust things, just get slushy and hard to move.

[Chinobi]

in a real SHTF kind of failure (requiring of course that you are present for it) you could drain a properly sloped system and recharge it when conditions improve.

[Avadon]

It's good to -40 in a 50-50 mix and then it won't swell and bust things, just get slushy and hard to move.

 

 

Amazing! Well worst it could ever get here is down to -5 maybe -10 in a very extreme freak chill. We are a hardiness zone 5.

 

And do you happen to know is that ethylene glycol or propolyene gylcol that they use?

[Sask Mark]

I've seen propylene glycol (phosphate based) used at a 40% concentration.  That gives an approximate temperature range of -36C to 104C.  

[Bentiron1946]

itsme seems to have a pretty good handle on how to size the system. Under floor heating is a good solution to keeping your feet from getting cold however I think the idea of good barrel stove is a lot cheaper to maintain but dose pose some risks of fire if you use flammable liquids on occasion. Under the floor is safer in this regard. 

[Avadon]

Does anyone have links to the anchors that you don't have to drill for? I can't seem to find them.

[Frozenforge]

The slab heating is usually done with several zones and they are fed by manifolds, that keeps the slab evenly heated but also provides a way of shutting off a section if a leak develops

As for mounting equipment, if you use an industrial adhesive to glue down a mounting plate you get a large contact area for the adhesive. If the footprint of the equipment is say 3ft by 4ft, gluing down a steel plate of the appropriate thickness would give 12 square feet. A good adhesive would be extremely difficult to break away with that much bonding area. Im sure there are some experts with adhesives that can make some suggestions.

[Avadon]

The slab heating is usually done with several zones and they are fed by manifolds, that keeps the slab evenly heated but also provides a way of shutting off a section if a leak develops

As for mounting equipment, if you use an industrial adhesive to glue down a mounting plate you get a large contact area for the adhesive. If the footprint of the equipment is say 3ft by 4ft, gluing down a steel plate of the appropriate thickness would give 12 square feet. A good adhesive would be extremely difficult to break away with that much bonding area. Im sure there are some experts with adhesives that can make some suggestions.

 

 

Yes this thread has more than convinced me to do the pex in the slab. As this is my last shop (I intend to die here on this property) it makes no sense not to do it. I don't want to be 65yrs old and kicking myself every winter for not having had it done and then desperately needing it because my circulation is totally shutting down. Ounce of prevention=pound of cure.

 

In the last year or two I took a lot of my small stuff.. bench grinders, buffers, etc. and build a small box 2'x2' under the legs of the stand. Lined it with 6mil vapor barrier and poured it level with concrete. It's just light enough you can still move it easily with a hand truck but to heavy to move when it's operating. It's worked quite well so far. Of course things like vices, and tables probably need something more like the adhesive as there are prying/torsional forces on them.

[Frozenforge]

There is a product called POR-15 designed to coat/prevent rust on steel. It requires the metals surface to already have a thin layer of surface so as it expands during the curing process it will penetrate the microscopic pores in the metal. They also promote it as a concrete paint because of the penetrating feature. I was painting some 2" square tubing about 12" long in the garage and one of the pieces was disturbed and fell over onto the floor and bonded to it! About broke my toe when i gave it a kick to knock it loose, ended up hitting it with a sledge hammer and it came loose, but it also left some of the concrete stuck to the steel!
Im sure there are much stronger actual adhesives that will work great.

Im pretty sure they use propylene glycol due to it being more friendly to the environment.

Alot of the big office buildings built up here in the last 10 years or so have slab heating in the outside sidewalks, stairs. They keep it just warm enough so that snow and ice dont accumulate during the winter. Im sure it pays for itself in the long run not having to pay for snow removal and avoiding slip and fall accidents

[Chinobi]

ok so i will suggest this after all, you are already halfway there.  if you want wall to wall pex, and the freedom to mount hardware on a whim without too much prior planning you can take your equipment footing boxes and establish a standard size, then when you pour the slab you can cast some kind of anchoring system directly into the slab.  if you set your anchors on a grid that mates with the standard size box you use for the footings then you can put your mounted devices wherever you want, in increments of 1 foot or whatever.

 

ill leave it to you to figure out how to detail the anchors, but before you dismiss it as a field of trip hazards my mental image is of an L anchor bolt set so the top is below flush inside a 2-4" diameter hole that can be plugged flush with a pipe end cap or something similar.

 

even a little better (though i dont know offhand of a product like this personally) would be a nut on some kind of anchor shaft and set flush or just below flush with the top of slab.  this lets you screw something temporary into it to prevent it from filling up with scale and other debris, and then install your equipment by bolting down into the floor.

 

look up simpson strong ties (www.strongtie.com) and give one of their reps a call, they may be able to refine your search a bit more or direct you to a concept that will be more in line with your needs, their 'blue banger hanger' was the closest i could find in a quick search, but it is intended for the underside of concrete roof decks to mount plumbing and the like.  take a look also at their short drop in mechanical anchors, they are intended to be shallow enough to not clip rebar, so the pex should be safe, but i didnt check their load ratings.

 

im sorry, i ramble.

 

forget installing anything for equipment smaller than a power hammer.  do it like a portable crane's counterweight; stacking sections.  incorporate a heavy solid base plate in your equipment mounts and then stack it up with plates or bricks or whatever is handy to build up the total weight from smaller more manageable weights.

[Avadon]

Thanks for all the good advice everyone. I'll definitely be researching those simpson strong ties. :)

[Chinobi]

im confused Av, you say you want to avoid having to pre-plan future equipment emplacements, yet you are actively chasing down ways to permanently install fixed anchor points at fixed locations and spacings to bolt down your gear well in advance of actually placing that gear.  that seems like more preplanning(to say nothing of material and installation costs) than providing whole sections of floor with no pex that can be drilled at will, and asking the contractor to provide a detailed as-built drawing of the layout, and leaving yourself some visual markers on the surface.  plus you leave yourself open to that network of anchors not fitting what you want to bolt down in the future unless you comit to building a mount for each one.

 

that said, i spoke with one of my co-workers who recommended looking at using Nelson Studs welded to the bottom of a thick enough plate set flush into the surface of the concrete, and then you can weld your mounts onto that and grind them off if you have to.  gives you more flexibility with your actual attachment points than the fixed anchors because you are not constrained to a single point.

 

http://www.nelsonstud.com/Portal/Portals/0/pdf/h4l.pdf

[itsme]

I don't know what type of equiptment you plan on mounting, but we have great success with "drop-in anchors". They are essentally an expanding nut that requires less depth than "red-heads" with the same pullout values. Typically a 6" slab is only nominally more expensive than a 4" slab, since there is basically no difference in the finishing or forming. You just have to pay for the additional concrete. That way you have 50% more thermal mass, and at least 1 1/2" depth to the rebar. The anchors are very resistant to shear and uplift, but im not so sure about vibration.

 

Frankly, unless you insist on it (and you should) the rebar grid will rarely be on what we call "chairs" (they look like a bigger version of the tripod that prevents your pizza from touching the top of the box). The rebar grid is often set on rocks and other crap spaced so far apart that it barely supports its own weight. Then the concrete guys trample it during the pour so that the tubing is smashed to the gravel. This should be prevented if you want the best performance from your system. I am seriously understating the importance of this step.

 

Photos are nice, but rarely provide enough detail to be sure of the tubing location. Especially since you can't measure to the outside of the slab once the walls are built (except in doorways). It really is easy to find the tubing with a digital thermometer if you know which direction the loops run. That being said, it makes me vibrate a little any time a hole is drilled. Best to section off mounting locations.

 

Good luck with your project!

[Avadon]

im confused Av, you say you want to avoid having to pre-plan future equipment emplacements, yet you are actively chasing down ways to permanently install fixed anchor points at fixed locations and spacings to bolt down your gear well in advance of actually placing that gear.  that seems like more preplanning(to say nothing of material and installation costs) than providing whole sections of floor with no pex that can be drilled at will, and asking the contractor to provide a detailed as-built drawing of the layout, and leaving yourself some visual markers on the surface.  plus you leave yourself open to that network of anchors not fitting what you want to bolt down in the future unless you comit to building a mount for each one.

 

that said, i spoke with one of my co-workers who recommended looking at using Nelson Studs welded to the bottom of a thick enough plate set flush into the surface of the concrete, and then you can weld your mounts onto that and grind them off if you have to.  gives you more flexibility with your actual attachment points than the fixed anchors because you are not constrained to a single point.

 

http://www.nelsonstud.com/Portal/Portals/0/pdf/h4l.pdf

 

I think you misunderstood what I was getting at. I don't want to have to plan out hard points or anchoring stations/positions. But I was curious though about anchors that you don't have to drill.. i.e you just glue to the floor. Maybe you were confused about that intention? The only thing I want to be concerned with during the slab is making sure I know exactly where the pex is. I think i'm going to make notches on the footer wall so that I can string line between and know exactly where the pex is. No pictures, no measuring, should be easy to know where that pex is at all times. Then I'll also make notches on the ends for where the loops will be and that whole area will be a no drill area.

 

I agree that putting anchors in the concrete a head of time is huge amount of planning. I'm just not feeling that. Chances are it might not even light up exact. I wouldn't feel comfortable doing that. Those nelson studs look great, but I'm hoping to find an anchor that I don't even have to drill for.

[Avadon]

I don't know what type of equiptment you plan on mounting, but we have great success with "drop-in anchors". They are essentally an expanding nut that requires less depth than "red-heads" with the same pullout values. Typically a 6" slab is only nominally more expensive than a 4" slab, since there is basically no difference in the finishing or forming. You just have to pay for the additional concrete. That way you have 50% more thermal mass, and at least 1 1/2" depth to the rebar. The anchors are very resistant to shear and uplift, but im not so sure about vibration.

 

Frankly, unless you insist on it (and you should) the rebar grid will rarely be on what we call "chairs" (they look like a bigger version of the tripod that prevents your pizza from touching the top of the box). The rebar grid is often set on rocks and other crap spaced so far apart that it barely supports its own weight. Then the concrete guys trample it during the pour so that the tubing is smashed to the gravel. This should be prevented if you want the best performance from your system. I am seriously understating the importance of this step.

 

Photos are nice, but rarely provide enough detail to be sure of the tubing location. Especially since you can't measure to the outside of the slab once the walls are built (except in doorways). It really is easy to find the tubing with a digital thermometer if you know which direction the loops run. That being said, it makes me vibrate a little any time a hole is drilled. Best to section off mounting locations.

 

Good luck with your project!

 

I hear yah. I've seen people just lay the rebar grid on the ground, right ontop of the insulation, before pouring the slab. What good does this do? Virtually none. I will insist on chairs and perhaps even something stronger if I think the guys are going to crush them during the poor. I saw those digital thermometers and they aren't terribly expensive.

 

I'll probably pound some rebar behind the slab where the runs are. Then when the monolithic is poured. Transfer those rebar spots to chiseled lines/notches on the inside footer wall. I got to imagine that would probably land me with 1/2" of each line as far as accuracy.

[archiphile]

I will say this: that after four years and many hundreds of thousands of dollars building our barn make certain that you can get a heating source that is sized for the space. We put pex in the tack room, just a small 12'x12' ( 144 sq ft.) space. It is the only room with insulation and heat. We were planning to use our tankless hot water heater but found that it is too inefficient and ALL of the boilers on the marked are sized for running entire houses in short we hat to purchase a second in room heater to use as there is not anything currently on the market that will run that small a space efficiently. I hope everything works out well for your project.

[itsme]

Archiphile, as you observed, tankless will not satisfy. I have installed several systems that ran off a dedicated electric hot water heater (running glyserol or something similar) for areas the size you are talking about.  Depending on the specifications, a small 12 gallon unit might be enough btu's to heat that room. Just hook a regular thermostat to the circulating pump, and you are in busness. Still, you would have to let it run all the time for satisfactory results, which will never be as efficient as just turning on a space heater in a room that is used infrequently.

[BIGGUNDOCTOR]

Look into infrared heaters like the ones Redwell makes, there is another company Austraheat (sp?) that is the same , but less expensive. They are not like the typical American IR heaters. The surface only gets to 200 degrees.

 

 

Personally I don't think a non heated slab will be an issue. How big of a shop are you making? If the building is insulated, the slab shouldn't get that cold. If you have issues with standing in one area, toss a mat on the floor.