75x42 Shop - Adding Concrete/Insulation/Heat

I've got a 75x42 shop that I need to finish the floor, insulate, and heat. It is a 20 year old Morton Pole Building with 12' sidewalls. Two 15x12 slide doors, One 12x12 overhead door at the end. I don't work in this shop for a living, so 50-60 degrees inside during winter months would be fine for me in southern Ohio.


Floor: Currently half the floor is conventional 4" concrete, the other half is 57 gravel. The existing concrete is decent but has a few good cracks, no drain, and an uneven gap at the 15x12 door. Seems to be 3 different pours, none is like the other. I am kicking around 3 options.

1. 6" concrete with wire to replace the gravel.
2. 6" concrete with wire, insulation, and tubing. Half the garage floor would be radiant heat. Possibly replace old 4" at later date with same.
3. Bust out the old and replace all with 6" concrete, wire, insulation and tubing.

Should I have concerns with a nonheated floor next to a heated floor inside the same structure? Obviously I'd need insulation between them in order to keep heat in the one pad.



Left of the blue line is 4" concrete. "Steel on this side" is the shared wall and has the furnaces on it.

Insulation: Currently uninsulated except for a shared wall with my house, which I assume is insulated. It has ridge/soffit vents and scissor joists. 4/12 top side, 1/12 bottom side. The 12x12 overhead door is insulated, however the 15x12 sliders are not.

I think my only decent option is closed foam. Everything else would be negatively effected by the steel sweating, except maybe foil lined foam panels. Even then, the condensation would find the cracks.

Would there be a problem with closing up the ridge and soffit vents and foaming it all in? I like this option because it allows me to keep the storage in my loft area and reduces 2 post lift issues.



End cut of the shop.

Heat: We currently have a central boiler [6048] that runs radiant floor heat in our home. The boiler already has a second pump for a second system. The garage also houses both of our aging furnaces/central air at the shared wall.

Although the easiest heat is force air from the electric furnaces, that would be my last choice for such a large space. I am leaning towards floor heat, some sort of boiler forced air option [blower radiators] or a large propane furnace with a boiler radiator inside that could be run either way.

Would I be correct to assume that if I keep an open truss plan radiant heat is the best option since any forced air would just rise to the peak? Is the cost and effort of floor heat overkill for my "hobby" use?


I know that is a lot guys, but all three have to work together so I wanted you to have the full picture from the start. I'm all ears.

Someone way more knowledgeable than I should chime in, but with closed cell on the underside of a metal roof deck, you'll run into moisture issues since the interface has no air flow to dry itself out.

Since you're in a northern climate, I would vote radiant flooring as the heat option. Breaking out the existing slab if money permits.

If it was my shop, go with all new concrete throughout. Don’t pour part of it new and leave the old uneven concrete. You’ll regret it everyday. Do you ever plan on having a fork lift? If so, use rebar instead of wire mesh.

Can you insulate the walls with bat insulation (without the kraft paper) and install sheets of metal over it from floor to ceiling? Though that route is likely getting close to the cost of closed cell foam. I honestly do not like the idea of spray foam directly on a sheet of tin. What if I need to remove that tin one day because someone backed into it? Or the roof is rusting out in 40 years, that will be a huge pain of spray foam is attached to the under side.


I’m south of I-10, can’t offer much advice on the type of heat. Though I read many folks use oil burning heaters up north. Down here, we worry about keeping cool instead of keeping warm.

Red Sleeper said:

If it was my shop, go with all new concrete throughout. Don’t pour part of it new and leave the old uneven concrete. You’ll regret it everyday. Do you ever plan on having a fork lift? If so, use rebar instead of wire mesh.

Can you insulate the walls with bat insulation (without the kraft paper) and install sheets of metal over it from floor to ceiling? Though that route is likely getting close to the cost of closed cell foam. I honestly do not like the idea of spray foam directly on a sheet of tin. What if I need to remove that tin one day because someone backed into it? Or the roof is rusting out in 40 years, that will be a huge pain of spray foam is attached to the under side.


I’m south of I-10, can’t offer much advice on the type of heat. Though I read many folks use oil burning heaters up north. Down here, we worry about keeping cool instead of keeping warm.

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I went with closed cell spray foam on my walls, covered by r30.ceiling was blown in r52. I had my barn house wrapped before they put the tin on just for the fact if I ever need to replace a sheet, it will come right off. This is my first year heating, but so far I'm at less than a dollar a day keeping a 36x40x14 at 60 degrees. If your interested in the full specs I'd be happy to share

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Also I forgot, most tin manufactures won't warrant there product if spray foam is applied directly to the tin, that was another reason for the house wrap.

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Nothing to add about the insulation since we talked, but I will second the remark about the concrete. Fix it all if funds allow, and do rebar instead of mesh, my contacts in the cement world say the wire mesh is worthless with the way most people install it. If you decide against rebar, he suggested to add fiber to the mix.

thatguy69 said:

I went with closed cell spray foam on my walls, covered by r30.ceiling was blown in r52. I had my barn house wrapped before they put the tin on just for the fact if I ever need to replace a sheet, it will come right off. This is my first year heating, but so far I'm at less than a dollar a day keeping a 36x40x14 at 60 degrees. If your interested in the full specs I'd be happy to share

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I remember your build, but can’t remember all of the details. What is your heat source? Glad you got your heat going. I have all of my tubing ran in the floor but the new house build started before I could get my shop 100% completed. Once I finish up some final touches on my house, then I can get back to the shop.

To the OP, I vote to replace existing concrete as well and go with radiant floor heat. My original plan was to run a wood boiler to heat my shop and house. I had considered a propane boiler but I’m nervous about fossil fuel prices and the incoming administration in the White House. Do you plan to seal up the slider doors in some way?

I have radiant floor heat with a propane takagi on demand water heater. Working great so far

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joefarmer said:

Someone way more knowledgeable than I should chime in, but with closed cell on the underside of a metal roof deck, you'll run into moisture issues since the interface has no air flow to dry itself out.

Since you're in a northern climate, I would vote radiant flooring as the heat option. Breaking out the existing slab if money permits.

Click to expand...

So I guess maybe I'll have to call a few places and ask about that. You think it would only be an issue on the roof or on all sheet metal? I was hoping to solve that problem with closed cell.

Red Sleeper said:

If it was my shop, go with all new concrete throughout. Don’t pour part of it new and leave the old uneven concrete. You’ll regret it everyday. Do you ever plan on having a fork lift? If so, use rebar instead of wire mesh.

Can you insulate the walls with bat insulation (without the kraft paper) and install sheets of metal over it from floor to ceiling? Though that route is likely getting close to the cost of closed cell foam. I honestly do not like the idea of spray foam directly on a sheet of tin. What if I need to remove that tin one day because someone backed into it? Or the roof is rusting out in 40 years, that will be a huge pain of spray foam is attached to the under side.


I’m south of I-10, can’t offer much advice on the type of heat. Though I read many folks use oil burning heaters up north. Down here, we worry about keeping cool instead of keeping warm.

Click to expand...

One big pour is not as much a money issue as it is putting everything outside for the time it takes to remove, prep and pour new. Forklift not sure, but tractors, excavators, and trucks up to Class 8 yes.

I agree with the foam on tin solving some issues but creating others. The wide bats of plastic backed fiberglass 8'x40' rolls and could in theory be rolled from floor to ceiling and in the ceiling with minimal labor. However, unless I find a better source the price is the same as closed cell and that did not include the steel covering.

I've lived south of I-10 before, it's all about not cooking in a steel building. Sometimes I miss that weather.

thatguy69 said:

I went with closed cell spray foam on my walls, covered by r30.ceiling was blown in r52. I had my barn house wrapped before they put the tin on just for the fact if I ever need to replace a sheet, it will come right off. This is my first year heating, but so far I'm at less than a dollar a day keeping a 36x40x14 at 60 degrees. If your interested in the full specs I'd be happy to share

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Did you have a thread on it? I can always wonder through it and read the details. So you are double insulated in the walls?

thatguy69 said:

Also I forgot, most tin manufactures won't warrant there product if spray foam is applied directly to the tin, that was another reason for the house wrap.

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My tin is far past warranty. But maybe I need to find some 1.5" foam board and slide it between the girts and behind the poles and seal the edges. I suppose I could also try to wrap from the inside, but I feel like that's a waste of effort.

Meyers Farms said:

I remember your build, but can’t remember all of the details. What is your heat source? Glad you got your heat going. I have all of my tubing ran in the floor but the new house build started before I could get my shop 100% completed. Once I finish up some final touches on my house, then I can get back to the shop.

To the OP, I vote to replace existing concrete as well and go with radiant floor heat. My original plan was to run a wood boiler to heat my shop and house. I had considered a propane boiler but I’m nervous about fossil fuel prices and the incoming administration in the White House. Do you plan to seal up the slider doors in some way?

Click to expand...

The wood is basically free, but it also requires a baby sitter if you're away from home for long periods of time. I don't drag, cut, split anymore. I have a source that fills my dump trailer and I touch it one time doing in. Pick your poison.

The slider doors are a hurdle. I had a overhead door guy tell me my truss design means reframing and steel work in the openings for an overhead door. I lose height and it adds about $750 to each door install price. I think I am going to attempt to run the sliders with insulation and creative sealing techniques and see how it goes.

JWhite said:

Nothing to add about the insulation since we talked, but I will second the remark about the concrete. Fix it all if funds allow, and do rebar instead of mesh, my contacts in the cement world say the wire mesh is worthless with the way most people install it. If you decide against rebar, he suggested to add fiber to the mix.

Click to expand...

Good info on the rebar/mesh, I should ask my concrete guy as well. I don't think fiber is too much extra to add, probably good insurance.

Doing the whole pad would certainly take a lot more planning that I have up to this point.

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Fiberglass bats: Pole Building Insulation Options for Insulating Pole Barns






Spray Foam for those who might not be familiar with it:


Foam Board:

EPS Foam

Yes double insulated. Closed cells main objective is to make the building air tight, as far as r value per dollar fiberglass is way cheaper hence the reason I paid for 1 inch of closed cell and put fiberglass over it. I paid for 1 inch but I would say it averaged more like 1.5-2 inches at minimum

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I got a quote a while back to closed foam the whole shop, walls and roof, for like $8000-8500 if I recall. My house could use some exterior and insulation fixes. So, one plan was to buy a foam machine/drums and do the whole damn thing as thick as I want for half as much. I planned to practice on one of the small barns till I got the hang of it.

Bersaglieri said:

I got a quote a while back to closed foam the whole shop, walls and roof, for like $8000-8500 if I recall. My house could use some exterior and insulation fixes. So, one plan was to buy a foam machine/drums and do the whole damn thing as thick as I want for half as much. I planned to practice on one of the small barns till I got the hang of it.

Click to expand...

I think Home Depot and Menards sell the application kits now

zstroken said:

I think Home Depot and Menards sell the application kits now

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I think I did the math on those small kids and the amount I would need costs more than hiring it out.



Where did you radiant heat guys buy pipe, manifolds, etc from? I'd like to crunch some numbers.


Any good sources for foam board in bulk?

Also, I found some low priced felt backed foam board. I'm assuming that is the least desired board due to steel sweat right?

Supplyhouse or pex universe. Make sure you get oxygen barrier pex, and also I made my own manifolds up out of stainless pipe fittings. It was a lot cheaper and turned out to be better quality than most you can buy online, but I get a pretty steep discount at fastenal. And I bought my foam 2nd hand from a place in akron. There's guys that buy foam from insurance jobs,it's still in perfect shape but cost me 1/2 as much that way. It was 3.5 inch eps, there's a big debate on xps vs eps. Xps has better r value per inch but holds water long term which decreases r value big time. Eps is softer, but does not hold water. If your interested I can dig up the number, they had both Eps and xps

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