# Under or Over



## AviatorDave (Mar 15, 2012)

Hey folks,

I have some thoughts to pose to you. I hope to be building a workshop in the next year or two and to fill the time with something other than just pining for the new space, I'm doing a lot of thinking about how to build it. It's going to be built from the ground up so now is the time to brainstorm for neat ideas. I live on 10 acres and the basic plan is to build a 40' x 60' pole barn with a concrete floor. The whole barn will not be used for the shop. Some of the space will house the normal stuff one accumulates through life and can't find room for. The barn itself will be uninsulated but the workshop portion will be insulated and heated. I haven't looked into how tall the barn will be so I haven't really thought about the ceiling of the workshop portion yet. What I've run across a couple of times from different people on different topics is the notion of building a false floor and running power under it as well as hot water pipes to heat the floor. This concept of a false floor could also possibly have benefits for exhausting paint fumes for a paint booth, running dust collection duct work and maybe even air hose plumbing. (Although I must admit that I prefer an air hose to be hanging above me on a spring to pull down when needed and retract up out of the way when not.)

The workshop will basically be a woodworking shop where my crop of woodworking tools may finally find a long term resting spot. This is to say no mobile bases. My thoughts before hearing about a false floor were the normal ones of having drops for everything. The thought of an uncluttered look with the false floor is appealing but in thinking a little more about it, I can foresee some problems with access to things in the event of problems or expansion/maintenance. I can't even say that I've pictured what the floor would be made of but I picture it sitting on top of the concrete.

It may be that a false floor was a great idea for computer server rooms back in the 90's and have no place in a wood shop . . . but since the project is still a ways off I figured that now is the time to dream and see if there are some good ideas out there.

So in summary:
Floor heat vs some other method?
Power under the floor vs drops?
Dust collection duct work under the floor vs drops?
Air hose plumbing under the floor vs up in the ceiling?
Paint booth ventilation as downdraft vs exhaust fan in the wall?
How would you build a floor like this that gave access and still supported the weight of heavy shop tools?

It all sounds very cool to me . . . but the engineer in me recognizes that form and function could be hindered by a poor fit and make it unpractical and possibly even unsafe if not set up right so the inclination is towards drops.

Do any of you have any experience with this? What would you do with your dream shop along these lines if you could? (or what would you *not* do?) All comments and advice are welcome on any or all topics!

Thanks!
-Dave


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## BensBeerStShop (Jan 8, 2012)

I don't know about a "false" floor, and don't have any real experience with this, but I have seen and read a lot about having utilities in the floor. Most I've seen that were concrete floors had the ducting, conduit and tubing for radiant heat laid in before the concrete was poured. It would take some serious planning to have everything where you will want it permanently, but with a space as large as you are planning, layout would be fairly simple IMO.


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## a1Jim (Aug 9, 2008)

Hi Dave
I have built my own shop an in fact I'm a contractor of 25 years. I wanted my shop ceilings high enough so I could stand 12' material on end so I made them 14' high,I like it that way but there are some things to consider,heating that much area takes a lot long in if your using a gas or any fuel you pay for it's going to drive your heating cost up. If you are hanging things on the rafters(I hang most of my jigs there) you will need a tall ladder or use a long stick with a forked end on it to hang things up and take them down. I have most of the things your talking about in my concrete floor and it makes life a lot easier. You use the term false floor I'm quite sure what you mean about that, but your talking about building a floor over a floor that doesn't make any sense to me. If you want all the things your talking about under your floor I would just build a wood floor with crawl space below it . That will make the the installation and maintenance of all of those systems much easier. Don't be that concerned about weight if built in the correct way you should be able to park a truck on it. I believe you will need to have both in floor and ceiling drops for air,dust collection. I think radiant floor heating is the best way to go heat wise. I would make sure you have a space for your air compressor and dust collector out side for noise and safety considerations.If your thinking of building a spray booth you want to consider having fans blowing air in and fans blowing air out with filter systems and a concrete floor with a drain system for cleaning up.I think your very wise to give all these issues a lot of consideration before building .


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## Manitario (Jul 4, 2010)

If I could build my dream shop, I'd have in floor heat; quiet, efficient and no air movement to stir up dust. I've seen some LJ's that have infloor electrical and DC, personally I wouldn't like to lose the flexibility of being able to change my shop configuration.


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## rkober (Feb 15, 2012)

I couldn't afford radiant heat in my shop when I built it but have it in my house now. It would be great in a shop. I would recommend a concrete slab either way (and not a false floor). Radiant heat in the slab requires some design considerations (including insulation underneath). The slab also acts as a thermal mass and is very efficient and comfortable. Consider freezing if it's an issue (you can run antifreeze in the tubing).

Like Jim I have 14' vaulted ceilings (at the eve) in my shop which I enjoy. We have part framed off that has a loft which now adds a lot of usable space.

Knowing what I know now, and related to your thoughts, consider running conduits to multiple locations for future use. You could pour hand holes into the slab with conduit drops to allow wiring machinery in the future.

Good luck. Someday I'd like to add a 40'x60' to my shop and build it the way I want.


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## a1Jim (Aug 9, 2008)

A couple points ,If you have a wood floor and a crawl space you do have flexibility to move you power,dust collection air,etc. because you have a wood floor and can patch any holes you make for your air or DC. Another way to keep your layout flexible is to have elec. air,DC above and below the floor ,when I built my shop I put in a 200 amp service and ran 220 and 120 outlets ever 6ft around the whole perimeter and some optional places in the floor.
Another point is radiant heat does not have to be in a concrete floor it can be installed under a wood floor . Even though I have a concrete floor wood floors are much easier on your body over the years. I think a loft is a good idea,but if I did that I'd go with a 16' ceiling height so you can stand upright while your up in the loft. Another item to plan for is storage for your material ,I find it taking over my shop and have not covered space outside due to my postage stamp sized lot.


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## ChuckC (May 13, 2010)

Radiant heat in concrete takes a long time to heat up (maybe even under wood too??). It may not be the best way to go depending on how many hours a day or week you will be spending in there. I only get a few hours a week, on average, in the shop so it's much cheaper for me to use a propane heater to just warm it up while I am out there.


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## muleskinner (Sep 24, 2011)

Myself, I'd prefer floor outlets for my stationary tools and a couple cord drops for portable tools. I like having my air overhead - the less stooping the better. Your heating configuration depends on what kind of heat. Most everything else I'd keep overhead because 1) there's more room and 2) I've spent enough time in crawl spaces.

*It's going to be built from the ground up*
That's the way I'd do it too.


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## Finn (May 26, 2010)

I have worked in computer rooms moving heavy equipment over "computer room floors" They are 24" square tiles supported at all four edges by a grid and just lift out to give access to the 9" or so space under the floor. The floor sets in this grid and is supported by, glued in place, vertical steel channels. An expensive floor for sure but maybe one could be made a bit less expensively. This would give you complete flexibility for exhaust, heat, electric power, compressed air etc.


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## canadianchips (Mar 12, 2010)

My first shop was 50ft x 50ft, arch style rafter building. I had a loft across the back, on top of my woodworking area. I advise to put radiant heat in the floor. You can run a header and only heat part of the floor if you want. Adding as you need to. Just put the pipe in BEFORE.I cemented my floor in 3 sections (As I could afford it) I lived in Sask.Cdn. We had freezing temp. from Oct 31 to end of April ! *#1:* The secret to floor heat is never turn heat off in winter ! Even when I wasn't in the shop I kept it just above freezing. When I needed it it DID NOT TAKE long to get floor to comfy temp. #2: you do not have to set thermostat at 70 degrees F. to be warm with in floor heat. A good working temp of floor heat was 55-60. 
The second thing I had was PVC conduit in the floor to run electric to machines. I did not have my DUST collection in the floor. My thoughts were less plugging going overhead. 
I also put 16"l x 4" d. pipe cemented into the floor , 2 rows every 10 ft. length of building .I made jigs that would fit inside these and could use them for roller stands, pulling autobody work or whatever. The one mistake I made. I only had 1 overhead door to allow vehicles in or out. In winter I had to open a 20ft. w x 15ft h door. I wished I had put 2 large doors in. 
You are on right track thinking about WHAT you want before you do it. It is CHEAPER on PAPER to make the changes.
Best luck with your shop !


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## AviatorDave (Mar 15, 2012)

Wow! This is fantastic advice! Here's a few more things to toss into the mix:

Since l live out in the styx, propane is the only gas source I can tap into. The house is heated and cooled via a geothermal heatpump and I'm pretty happy with it. To the extent that I'm considering putting the same thing in for the workshop. What are your opinions on how to provide the energy for the radiant floor? (seems like most people are in favor of a radiant floor) Circulated hot water or hot air? I've used to have a home with a boiler so I'm a little familiar with closed loop hot water systems but not sure about closing a loop for hot air. In theory they're both fluids, I think water is probably more efficient at holding heat. I'm sure I could use a geothermal system to heat water . . . Just don't know enough about it yet to know if that's the right way to go. Also, it seems that putting the radiant system in and pouring concrete over it is the most talked about method . . . but I'm intrigued by the wood floor concept as well. I'm not all that jazzed about a crawl space but I agree with a1Jim that if it's built right you should be able to park a truck over it. Thanks to Jim Finn as well for covering the floor over a floor concept. That's exactly what I was thinking of. I don't honestly know if that's still used for computer rooms but it seemed like a great concept. Not really a crawl space but more of a floor that was really easy to take up to add/subtract/change layouts. I would not be excited about having to tackle a plugged DC line in a floor but if the DC components weren't glued together and could be disassembled, a false floor would make it easier to get to. That said, If you have a false floor, that also means a lot of dead air space. How might that affect a radiant heat system? I picture a subfloor heating system still being a closed loop of some kind but this question speaks to whether the plumbing is encased in concrete or floating free under a false wood floor. Will I be losing out with heating dead air space vs warming up concrete or vice versa? Also, if I wind up with a tall ceiling, is this still trouble for heating the shop in that most of the heat will hang out at the top? I mean, I know the heat will rise no matter what but there's a big difference in blowing hot air out into the shop airspace vs getting the heat from a warm floor. I suppose some ceiling fans would still fulfill the same purpose for pushing heat back down if this were an issue . . .

Hey canadianchips - Do you have any input on the cost of keeping the floor just above freezing in the winter and raising it while you're in it? That seems like a good way to go . . . and that idea for putting in a header and being able to compartmentalize the floor into heating zones ROCKS!! I'm all about that idea!!

I think I'm sticking with my thoughts on having the air drops from the ceiling . . . for now . . . Seems silly to connect the hose at the floor just to string it up above me. I just like the though of having it up out of the way. Anybody have any arguments for coming up from the floor? Speaking of the ceiling, I like the idea of a 16+ ceiling with a loft but I've also been planning on having material racks at one end of the shop somewhere. (haven't put together a floor plan yet) I too have been the victim of scraps taking over my shop. It gets annoying but darn it, it's hard to throw out a perfectly good piece of wood!!

Thanks again for all the great input!! You folks are giving me lots to think about!


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## a1Jim (Aug 9, 2008)

Dave 
Sounds like a good plan using a geothermal heat pump. for your flooring. I think everyone talks about concrete for radiant because that's what there familiar with. I've seen a number of folks who put it under hardwood floors including good old Norm http://www.thisoldhouse.com/toh/asktoh/question/0,,357313,00.html As far as having over and under air and electric in my mind is no big deal. I like it because you don't have cords or air hose under foot or hanging in your face. I have mine in the floor so it comes up right where my work tables and benches are along with long strips of plug ins on my benches and work tables I also have electric,air around the whole perimeter of my shop so if I change the layout I have power and air every where. I have a concert floor that I built what one might call gutters of small chases for my air ,power and DC it works fine but involved very good planing and I have a 1/4" steel plate on top so it can't be removed for alterations. This also require very good concrete finishing. If you have a floor over a floor your wood floor will need to be around 6" or more to run you DC that's going to require a lot of little braces or I beams of dimensional material that would need to be 12" . It's something that can be done but could be challenging. Plus the aspect or dealing with in floor heating.


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## ChuckC (May 13, 2010)

I think saying radiant heat takes a long time to heat up, or not, is relative to what a person thinks a long time is. I have radiant heat in concrete in my house and it can easily take a couple of hours to feel the floor get warm and the burner is running almost constantly while it's doing it. For the little time I get to spend in the shop this would not be cost effective. If I was out there every day then maybe I would think different.


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## mr500 (Mar 28, 2012)

Great Info


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## pintodeluxe (Sep 12, 2010)

I would go with a PTAC electric heat pump. Most affordable option for heating and cooling the shop. I don't mind drop-down D.C. and electrical where needed. The things that worries me about in-floor DC is what if it clogs? Or what if you want to move it later? In a crawlspace floor it could work well.


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## rkober (Feb 15, 2012)

Dave:
1) Typically water is used as it can carry more energy per volume (and steam much more than water!).

2) Radiant does not need to be in a slab and it doesn't even need to be in the floor (however the floor is the most efficient). In a subfloor and stapled underneath, for example, you need to put insulation underneath to drive the heat up through the subfloor (which is an insulator of sorts).

3) I use a geothermal heat pump in my house coupled with radiant (slab and thin slab on the subfloors). It's efficient and works great. However there are design considerations that make the system (and design) more complex. It's not uncommon to see 400-500% efficiency (actually called coefficient of performance or COP).

4) FWIW when I fire up my heat in the fall I'd guess it takes several hours to warm the whole system up from 60 deg (?) to 70 deg. I would expect any slab to take an hour or two (even with an oversized boiler) to heat from 55 deg to 65-70 deg. With that being said, radiant is more comfortable at lower temperatures comparatively. You don't waste as much heating the air in the ceiling and if you open an overhead door you don't dump all the heat out.

Let me know if you need a mechanical engineer


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## wormil (Nov 19, 2011)

If I were building a shop from scratch, there is no way I would have a bare concrete floor unless money was tight, a raised floor would be a no-brainer. At a minimum I would lay a hardwood floor over the concrete. Electrical run through the floor and along walls, dust collection overhead, air drops from the ceiling.

Not sure about the installation costs of geothermal vs savings but if you have it in your house then you've already made that decision. High efficiency heat pumps are money savers over propane but may not be practical if you are far north. In floor heating would be a nice luxury but I assume they are expensive to run. Advertisements touting them cheaper than gas assume you will only run them for a couple hours each day which doesn't make sense if it is your sole source of heat.


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## AviatorDave (Mar 15, 2012)

Again, more great advice! I find myself thinking about how to build a wood floor over a concrete slab. My deck building experience comes to mind with a system of joists and beams but I don't think I would want to deck it with deckboards. Too much of a pain to put down, things wouldn't roll well over it and definitely a pain to take up if you needed to get under it. For the actual floor surface I'm thinking along the lines of panels some how . . . Possibly sheets of 3/4" plywood . . . if a panel were damaged by something it would be easy enough to replace. Once the tools were in place there wouldn't be a lot of abuse to the floor. If the beams were spaced correctly it would be very solid. Using hardwood for flooring sounds quite nice but for the area that I'm planning for my shop space, it also sounds very expensive. Until I win the lotto I have to be realistic about cost where I can. For any of you who have built decks, you know about the spacing considerations with joists . . . the more joists the stiffer the floor but you can start to lose access to the space underneath it. The radiant heat system could be built in and once in place probably wouldn't need much changing, if any, if done right the first time. Electrical wouldn't be tough to route/re-route either. DC would be tougher . . . having the space available for the ductwork would be doable but it would cause the floor to be up higher and possibly cause heating concerns as far as dead air space. It could also be set up so that the deck beams were laying directly on the concrete (assuming it was level) and holes could be cut where needed to run PVC ductwork . . . Would be difficult to reconfigure though . . .Might be easier to actually have the beams up off of the concrete and run the DC plumbing underneath it. Toughest part there is moving around 10' sections of PVC under the floor . . . or even getting them down there to begin with after the deck frame is in place. Maybe use 5' sections and more couplings? I could plan for DC ports all around the floor just like electrical so reconfiguring would be rare. Blast gates used to control sections would make reconfiguration a matter of opening or closing gates rather than moving plumbing. Laying insulation in to help with the dead air space is a good idea . . . As long as bats were used it could be easily pulled up and put back down if you needed to get to something. Would have to consider joist spacing and available bat widths. I'd likely keep the floor temp on all the time but low in the winter and boost it while working in the shop. I'm usually pretty comfortable in a 55-60 degree environment when I'm moving about and working. That's a little chilly for sitting on a shop stool and hanger flying but then . . . that's what quilted flannel shirts are for.

I live in northern Indiana so our winters aren't too bad. (especially this year! WHAT is up with Mother Nature?? 80 degree days in February?? I'm tellin' ya . . . we're gonna pay for this somewhere down the line. Hopefully not with snow on Memorial Day. ;-) But I digress . . .

My geothermal system for the house came with the house when we purchased it so I'm still learning about it. I'm wondering, since the geothermal heat pump can heat and cool, how I might apply this to a radiant heat floor. I wonder what kind of configuration I would need in place to use radiant heat in the floor yet still be able to take advantage of the cooling mode. I'm guessing you'd still need some ducts to pump cold air. I don't think a cold floor would work well. Need to pump that cold air up. I guess this speaks to heating a liquid for the floor and using cold air in ducts in the summer for those 90+ degree days in august when just a fan doesn't quite cut it.

Can anybody shoot holes in my deck style floor idea? Sound interesting or silly? I would basically have a contractor pour a concrete floor for the entire barn and I would just build the deck (maybe a 12" deck?) on top of the concrete for the shop side of the barn. Could have a couple of steps down to the non shop side of the barn. Placement of overhead doors and entry doors would be easy enough to plan for. The barn itself will have to be built into a bit of a grade so having some of it sunk into the ground might help on the shop side as far as stepping into it from the outside entrance. (I can picture this clearly in my head but I realize that what I'm describing may not make as much sense. Let me know if something doesn't sound right)

Any better ideas? I'm all ears!


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## doyoulikegumwood (Jun 21, 2007)

so I'll give you my input on this as my last shop was a pole barn. 1 Dont hesitate to at lest put the piping in the slab for radiant floor heat it is by for one of the most efficient ways to heat anything and pex is cheap. I like the idea of using a computer floor. Why you may ask well half of my pole barn was a garage and you guessed it the other half was my shop. I was able to get my hands on a computer floor for free that being pulled out of a building. and thought this would be awesome and to tell you the truth it was. The thing I really liked about it was i wasn't locked in to machine placement at all if i decided to move my table saw i moved it and the tile that has the hole in it. my thought on a computer floor would be that the heat from the concreat would radiate through the computer floor.

Another thought on the radiant heat if your heat pump field is large enough you may be able to tap into it and i hear a lot of folks saying it isn't efficient because it takes to long to heat up and it will run too long to warm up the shop. my thoughts on this having worked in the heating a cooling industry unless you are not going to go into the shop for weeks on end shur shut it down. but it is far more efficient to keep the shop at 50 degrees and turn it up when in the shop then to turn it off letting the temp drop to say 20 degrees and then make the system work its way back up to a comfortable temp. your heat pump would do a great job of this with a water heater backup for colder days I like electric water heaters for this application as they can be set up to heat water durring off peak times.


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## wormil (Nov 19, 2011)

Twelve inch high deck sounds on the high side. It will have concrete underneath so the joists don't need width for strength, just enough space for electrical.

Could the same geothermal unit warm water running through the floor? Even if it were just warm in the winter it would make a big difference.

If you'll have whole shop dust control, consider putting a duct on the floor (can be along a wall) that you can just sweep dirt and sawdust into and can be closed off by a blastgate.

I've seen floor electrical outlets with flush covers. You could just put them in all over and you'll never have to move electrical.


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