Really need 24"vert insulation for radiant floor install

[Jesk12345]

I have a 30x40 pole barn I am going to turn into a garage. Currently there is just a dirt floor that I need to dig out and prep for radiant floor install. I am having a little trouble with some of the details however.

I know I have to put compacted gravel down first, how much is really necessary 4,6,8 inches?
Correct me if I am wrong isnt is gravel,vapor barrier,2"formboard,wire,pex,4-5inch concrete?

I see alot of people post I need to put a 24inch vertical barrier around the interior perimeter. So 24in from where the top of the floor will be? If so, looks like im digging 24inchs of complete floor out correct? Or does the perimeter foam sit in the dirt?

I am not sure how deep the 6x6 post are set in the pole barn, or if they are on concrete or just buried but when it comes to putting a foam perimeter in what do I do around the posts? Just put foam around the contour of the post?

 

[kj_mustang]

You have it correct. Minimum 4" gravel, then vapor barrier, then insulation, etc. I am not sure you need to go down since you do not have a footing. I did not do that with my pole barn. I cut and nailed the 2" xps foam vertically to the skirt board and it went down to the vapor barrier. I then put the foam sheets down on the vapor barrier. I also used 1" eps to isolate the poles from the slab. Here is a picture of mine.

 

[Rookie2]

I dug down the inside perimeter and stood up the 2" foam board. I have a few dents in my steel as a result. I believe it has helped . I also poured a square floating pad and insulated between the posts so that there is around 5" x5" of foam out to the skirt. Its a lot of work but a friend poured his out to the skirt and I believe he is paying for it in lost heat.

Rent a roller and compact any dirt you dig up or loose gravel.

 

[Jesk12345]

I could probably get away with digging down 15 inch then right? Around the perimeter I have 2x6 skirts that go between the 6x6 when I get down 15in can I just lay the 2" foam against dirt and skirt? Obviously I'll have excess insulation that will just get cut at the floor level. Also when it comes to the door openings just dig down and slap the insulation against the dirt?

 

[rburke65]

It might really help us to know if you live Miami or in Nome, Alaska........

 

[larry4406]

All of these slab insulation schemes seem to be for slabs on grade.

Anyone have details showing how to do it for a structural slab with grade beams and turn down at the garage doors? i assume the grade beams get boxed in insulation as well.

 

[theoldwizard1]

I dug down the inside perimeter and stood up the 2" foam board. I believe it has helped.

This is EXTREMELY important and frequently missed ! You should go down as far as the frost line in your location.

 

[theoldwizard1]

More insulation is always better, so if you afford 2 layers of 2" foam board, do it !

If you are doing 2 layers and place the second layer so that no seams land on top of seams in the first layer and then tape the seams, you probably don't need a vapor barrier.

 

[Jesk12345]

It might really help us to know if you live Miami or in Nome, Alaska........

Haha id put my boiler in my garage if I lived in Alaska!

Clarington Ohio is where I live

 

[Jesk12345]

Got the garage dug out, just need to do some more prep work for the insulation.

I am having trouble locating 2in EPS insulation. Everywhere lowes,aces,homedepot is wanting $40 a sheet!!! I swear Ive read where people were getting it for half that?

I have found some 2.5 inch on craigs but not too descriptive on specs so I am a little hesistant to pull the trigger on that. Its $12 a sheet though.

Any suggestions for insulation would be a great help. Willing to travel Ohio,WV,PA to pick up.

 

[Jesk12345]

Picking up my insulation next week. Just wanted to find out if I need to put any sort of barrier on the perimeter behind the insulation I put up or is it okay just to set on the ground and attach to the wall where I can?

 

[Highbeam]

Holy ****, you didn't dig the whole floor down 2 feet did you? I expected to see a ditch around the perimeter down to the frost depth.

Yes, you need to insulate the sides of the SLAB but below slab grade is less important if you also have insulation under the slab. Frost line max to prevent heave.

 

[Jesk12345]

Holy ****, you didn't dig the whole floor down 2 feet did you? I expected to see a ditch around the perimeter down to the frost depth.

Yes, you need to insulate the sides of the SLAB but below slab grade is less important if you also have insulation under the slab. Frost line max to prevent heave.

Oh I dug out alot haha, the clay is so tough it was just easier to dig out alot extra, most places arent 2ft, around the perimeter is but middle definately has alot removed also.

So Im okay just to lay the 2" insulation against the wall and start filling the garage back up with dirt? I don't need any VB on the perimeter? Only below the slab?

 

[Highbeam]

Yes, a continuous vertical 2" foam board all the way to the top of the slab and all the way around the perimeter would be awesome. A couple of nails would help hold the foam vertical and in position as you backfill. You need to compact that soil in no more than 6" lifts. Properly moisten the soil, it can't be bone dry to hit maximum density. Rollers, plate compactor etc, not your bobcat which is designed for low ground pressure.

You could do it all with crushed rock too.

Don't leave any voids behind the panels or anywhere else. It's tough to get the vertical foam backfilled perfectly.

So your poles are now 1/2 undug right? Hope for no wind.