Insulating Garage Floor

[gotbusa1338]

Hi All,

Been browsing for a few months, got some great information already. Building a 24 x 40 x 12'4" steel sided pole barn. insulating the roof and walls. Trying to decide if I should insulate the floor. I live in south jersey and we get a few months of cold but not a ton. I don't intend on heating or cooling the building full time. but I might put a propane heater for warming up the building when i work out there in the winter. I am not doing radiant floor heating. I know i wont be able to go back and do it later but if it doesn't really matter I can put that 12-15 hundred to better use elsewhere.
thanks for your time
Chris

 

[Tazzie]

Yes you should. The use of 4x8 sheets of foam will help keep moister from leaching into the concrete, will also help keep the concrete from freezing when not heated and that will help with cracking. If you lay on the floor it will also be warmer. Most people do not realize that most of the dampness in there garage comes up thru the floor. I used plastic then 2" foam then another layer of plastic then poured the cement.

 

[MagKarl]

I would not insulate the floor if you are not going to heat it. That money can be better spent.

My advice is to buy a bunch of used tools off of Craig's list for pennies on the dollar, some new coveralls, a creeper, case of beer, and really enjoy that new barn.

 

[RegeSullivan]

I would insulate it. Even if you are not going to heat it now you may in the future. There is more to doing it correctly than just tossing down some closed cell foam. Be sure to do a little research to get the most out of your money and the labor you put into it.

 

[GYPSY400]

If your not going to heat it full time I would say no.. Insulating the pad will only benefit if you can keep it warm. Heating the garage the odd day here and there will never get the pad warm. You may want to reconsider your heating option.. Even a ceiling mounted reznor on a programable thermostat makes it nice.. Doesn't have to be 70*.. Only about 50-55* constantly and crank it up to 65* when you want to work in there. In that case, then insulate the pad as the pad will hold the heat.


Sent from my iPhone using Tapatalk

 

[indyjps]

Definately use visqueen/plastic under your slab. I heat my shop when I'm working in it to 55. You can feel the cold from the floor .

 

[gotbusa1338]

Thanks everyone, I definetly planed to put a vapor barrier over the gravel. I might bite the bullet and insulate it. Any one have ideas where to get the xps foam for reasonable price. my HD and LOWES have it but it is probably going to cost 12-15 hundred just for the materials.

 

[bd8134]

You could spend your money more effectively in other areas.

 

[overkill 19]

It was cold out when I did mine .. Prob -18C. I noticed instantly when I laid the 2" SM on the floor how much warmer it got. I'd do it again in a second. My floor is not cold to lay on.

 

[overkill 19]

I got couple yards of sand to spread out over entire floor to fill dips in floor as best I could. I bought 4x8x 2" sheets, harder to find but way easier to lay. Imo

 

[dogdas]

You will never be able to recover that money in 20 years even using NG as a heating fuel. Most heat loss is in the lid and then the walls. Remember you are going to heat it part time.

 

[overkill 19]

Wood pellet stove might be a better option for heat than propane for sure

 

[dirttracker18]

My buddy insulated under his slab and rarely heats. There is a noticable difference in floor temp all the time. That sold me right there. I will always insulate under the slab as it is far more comfortable.

 

[bd8134]

Not sure about Canada but check your local code. A garage is typically not an approved location for a pellet stove. For a garage a wall hung heater is a much better solution for gotbusa1338. You don't loose valuable floor space & clearance in front of it and no need to store pellets and clean the unit.

 

[overkill 19]

Not sure about Canada but check your local code. A garage is typically not an approved location for a pellet stove. For a garage a wall hung heater is a much better solution for gotbusa1338. You don't loose valuable floor space & clearance in front of it and no need to store pellets and clean the unit.

I know wood stoves are not allowed. But I wasn't sure about pellet stove.

Good point check it out before ya buy!

I had a wood stove in the shop on the farm. Loved it. Drank lots of beer around that thing.

 

[walrus]

How much is comfort worth?, in a cold climate I'd never not insulate a floor again

 

[whitedogone]

warm shops are cool!

 

[overkill 19]

How much is comfort worth?, in a cold climate I'd never not insulate a floor again

I know I feel it was money very well spent

 

[Tazzie]

You caan always buy tools and toys for the garage later but you will never rip up the flool it insulate it later. Good luck with your build.

 

[1grnlwn]

Just looked at local Menards price for 250 psi 2"foam. $27 a sheet. Outrageous! 4 or 5 years ago it was in the high teens. I thought the price might go down when oil did but so far, No.

 

[gotbusa1338]

Thanks guys, i am trying to find a better price from a distributor. I know i wont be able to do it after so i dont want to regret not doing it if it will help in the least. Will post some pics as I get going. just finished clearing and bringin in fill to level the site. hopefuly next week getting it compacted and perfectly level.

 

[MagKarl]

Heat flows from warmer temps to lower temps. In an unheated shop, a winter source of warmth could be the ground, depending on your location of course. Same thing for summer cooling. Think root cellar.

You need to consider what ground and air temps you are dealing with to decide which way the heat wants to move, and where insulation could benefit you first. Insulation doesn't make things warmer, it simply slows the flow of heat.

Hate to see you spend the money and end up with a slab that's actually colder than if you'd skipped it.

 

[BobRae]

You will never be able to recover that money in 20 years even using NG as a heating fuel. Most heat loss is in the lid and then the walls. Remember you are going to heat it part time.

That statement is not neessarily true. You lose more heat through the floor than you realize. I'd check building codes for your area before relying on the experts here. Or, use an online heat loss calculator to show how much heat you'll need with vs without an insulated floor. There is also a comfort factor when working under a car on a creepy crawler.

 

[RegeSullivan]

Of all the guys that thought about it before they built... I'd bet there are more who regret their decision not to insulate the floor than those who did insulate.

 

[tightwad_wrencher]

Of all the guys that thought about it before they built... I'd bet there are more who regret their decision not to insulate the floor than those who did insulate.

This ^^^. The garage that was built on my property wasn't insulated. I don't think they even put a vapor barrier down. Heck the damn thing didn't have gutters on it when we moved in!

 

[xyster101]

You can do radiant heat tubing for cheap. $300 for 1000' lex on Amazon. Can always add the heat later. I did 2" foam under my slab 2 years ago and pex. No great out there but my floor is bone dry.
Insulate it now. Easier to do it now

 

[amdskip]

How much is comfort worth?, in a cold climate I'd never not insulate a floor again

What he said x100.

 

[JACDes]

if you never heat the slab will be susceptible to freeze/thaw action.

The insulation raises the frost line beneath the slab, if done correctly this means the ground below the slab cannot freeze.

This known as a frost protected slab.
The same technique can be applied to the foundations & footings creating Frost Protected Shallow Foundation of FPSF.

I offer this up for your reference.

http://www.huduser.org/publications/pdf/fpsfguide.pdf

refer to the charts for min, recommended insulation thickness for your region.
The techniques are a bit different for heated versus unheated structures if you plan to heat later on err to side of caution and design as unheated. This is how I approached my build and I have no regrets because the slab will never heave / settle / crack

 

[machsnell]

i insulated my slab on a angled shape 50 x 28 floor and did 6 mil vapor barrier. I also did the sides that come up to grade. I did 3" higher that avg psi foam boards rebar and microfiber. microfiber is not expensive but a worth investment in your concrete if you dont want cracking or to minimize your controls joints.

insulate the sides and under, it makes life more comfortable.

2 cents

 

[machsnell]

oh and learn from my mistake....put the tubing in the floor. its a pain in the **** to have to know where the tubing is for when you put lift in but do it

its cheap and i soooooo wish i hadnt been in such a rush and i had put it in.

 

[whitedogone]

You don't need 2" of foam.

http://www.ecofoil.com/All-Products...ion - Exact&utm_term=double bubble insulation

 

[JACDes]

the actual thickness (R-value) of the insulation under the slab depends on your geographic location.

to say "you don't need 2" of foam" is grossly mis-informed. if you need specific R value 2" may be the only practical solution.


The correct foam board for under slab use will also have higher compressive strength than this suggested bubble wrap which will have no effective R value once any rebar and concrete is placed and pops all the bubbles in the process.

 

[whitedogone]

the actual thickness (R-value) of the insulation under the slab depends on your geographic location.

to say "you don't need 2" of foam" is grossly mis-informed. if you need specific R value 2" may be the only practical solution.


The correct foam board for under slab use will also have higher compressive strength than this suggested bubble wrap which will have no effective R value once any rebar and concrete is placed and pops all the bubbles in the process.

Although technically you are correct. The building code (IRC and the IECC) only requires a certain R value for the outer 4' on the structure for slabs on grade. My response was based on the OP pricing 2" thick insulation for the entire floor area. R value is not the only factor in the equation here. In the case of infloor heat system, the radiant portion of the equation is huge. We have used radiant double bubble in over 2000 slab on grade installations for over 10 years now. We have done sheds all the way up to large commerial earthmoving equipment repair facilities and have never had a "compression" issue or damage issue with these products. In fact, the radiant barrier comforms to the subgrade whereas the solid foam board does not (therefore leaving voids). In addition, the Mechanical Engineers that did sizing of the infloor systems in the large projects we have done undersize these systems when this approach is used over solid full coverage foam.
My 2 cents, Use 4' of R10-2" EPS on the perimeter. You can install it horizontally or vertically or 2' down-2' in, etc. Don't forget to install to the TOP of the floor slab (you can put a 45 degree chamfer on the top). Then cover the entire floor area with radiant bubble wrap. As always, check with the local AHJ for proper R values for your area and call for inspections before placing any mud. Good luck

WDO

 

[jerseywild]

I am from South Jersey so I know your weather. I moved out to Washington State and bought a house with a 30X36 shop. I know the floor is not insulated and it gets wet just like the garage I rented in South Jersey. If I was building I would insulate the floor.

 

[beakie]

I know wood stoves are not allowed. But I wasn't sure about pellet stove.

Good point check it out before ya buy!

I had a wood stove in the shop on the farm. Loved it. Drank lots of beer around that thing.

I know wood stoves are allowed... atleast here in Ontario they are.
My insurance inspector looked it over, measured as per specs and gave it the OK. Costs me an extra $45/year, worth it!

my buddy built a shop years ago, DIDN'T insulate the slab...
regretted it that summer when the humidity hit the floor and we had to squeegy off the condensation
regretted it again that winter when he heated it... and still had to lay mats down to work on. Not just to lay on, but when standing on the cold floors for so long your feet would get cold.

unless you can wear the same shoes in the summer as you do in the winter (basic judge of temps), I would plan to insulate (and atleast plumb for in floor heating) any shop I even thought of building.

as said above, won't find many who regret doing it... but plenty who regret NOT doing it.

 

[B&H]

I would insulate it using the proper foam board, 2". I own an auto repair shop just outside of Syracuse, NY and we used the foil stuff under the slab in the old section of the shop during a floor renovation around 2008 and then last year we used 2" XPS or whatever it's called under the slab in an expansion in 2013. No doubt the floor with the foam board is warmer. Both parts of the shop have radiant floor heat and I feel there is noticeably less heat loss in the new section w/ the XPS.