Insulate a garage floor - new construction

[DRRummel]

I just got permission from our county to build a tall garage in my back yard. I wanted 12 foot walls so I can have an auto lift. The lift calls for a minimum 4" pour with a 3000psi concrete. I am thinking of upgrading to a 6" pour of 4000 psi concrete. The walls and ceiling will be 2x6 and insulted. The garage doors will also be insulted (Overhead door series 490 with R17.5). While talking to a builder about heating the garage to 50* with a heat pump, he suggested putting insulation under the floor slab. I thought that was a great idea. Then he left and I started to wonder how well that would work under a two post auto lift designed to lift 9000lb. Will 6" of concrete hold the lift and a car? Or will the insulation compress under the weight and cause problems. Any suggestions?

 

[lovesun]

I've done exacly what you describe, a 6" pour of 4000psi on insulation, however you need to use a harder insulation than used for a house. I have a two post lift in my garage and it has been showing no signs of cracking yet after 5 years.

 

[DRRummel]

I've done exacly what you describe, a 6" pour of 4000psi on insulation, however you need to use a harder insulation than used for a house. I have a two post lift in my garage and it has been showing no signs of cracking yet after 5 years.

Thanks for taking the time to reply. What would be a 'harder' insulation? The whole under the slab insulation has NEVER occurred to me before. If someone could throw out a couple of brand names or types, I will just repeat them to the builder. He should be able to figure it out from there.
Thanks for the help.

 

[sneezer41]

personally I would not waste money on extra concrete. Pour pads 8 inches thick where you want the lift to go. Blue stryrofoam under, 2 inches

 

[DRRummel]

I will need some crush-n-run fill to fill the low side. I believe this fill will need to be tamped before the concrete is poured. So the insulation goes between the earth and the stone? Or between the tamped stone and the slab? Tamping the stone with the insulation underneath will ruin the foam, right?

I think the sequence is:
a.Pour the footers
b. Call the inspector
c. Built the block wall (below grade and the two knee wall)
d. Call the inspector?
e. Fill in around the foundation walls and the low spots to a level grade.
f. Tamp the fill
g. Install 2” foam installation under slab
h. Install vapor barrier.
i. Pour the slab.

 

[sneezer41]

fill
foam
vapor barrier
steel
concrete

 

[Maulerman]

What about pouring piers under lift legs? That would save on making the whole floor thick enough to support weight.

 

[UnSub45]

I am adding a lift in my garage as well and I did insulate the slab. I did 2' x 4' piers 18" deep where the posts will go. I did not insulate under the piers.

 

[Kapt]

I used Dow Scoreboard. It comes in 4'X8' sheets and I think the cost is between 25-30$ per sheet for 2" thickness. I put in the stone, followed by the vapor barrier and finally the foamboard.

 

[DRRummel]

I think I have what I need to know. I am sure I will think of more questions when I actually start doing it.

I just got a price to parge the 3' block wall. Approx. 300sq ft. 950.00! That was more then I expected.

 

[5wndwcpe]

I just purchased OC Foamular 250 for my build at $21.00 a sheet from Homeless depot. Only thing is to get that price you have to buy 48 sheets. Not 47. Not 49. 48.

 

[Chris J]

To reiterate: the vapor barrier goes UNDER the foam.

The standard blue foam board is rated at 25 psi. There are other (more expensive) foam boards that are rated as high as 100 psi. However, it would be better to pour peers for the lift and then install the foam around them.

 

[DRRummel]

To reiterate: the vapor barrier goes UNDER the foam.

The standard blue foam board is rated at 25 psi. There are other (more expensive) foam boards that are rated as high as 100 psi. However, it would be better to pour peers for the lift and then install the foam around them.

Thanks. The lift vendor (GregSmithEquipment.com) strongly suggest not mounting on peers. The deal is that the vendor wants the mounting bolts to be drilled thought the foundation. That way if the lift has to be moved (concrete cracks or you move) the bolts can be driven into the ground beneath the slab and the lift doesn't need to lifted up off the bolts.

I was very clear that I wanted to to put J shape anchors in the concrete pour instead of the the wedge anchors. I would be more comfortable that the J anchors would not pull out. All I wanted was a template or measurements to use. Their final word was that the installation could very by 1/4- 1/2 inch and that 'all the other installation use wedge anchor and never have a problem.'

 

[sharpe427]

My lift vendor nixed piers as well. I had them do the install prep, an they put in a 1" bolt about 9" long with a 12x12x1/2" plate under the slab. Same reason given..if you want to move the lift, drive the bolt in ground. I feel very comfortable that the lift will never pull a 12x12 chunk of concrete out. I used a 6" 4000lb pour. The plate went in about 4" deep. After the slab dried, they milled a solid steel plate to go over the bolts and level the lift pads, then the lift was bolted on and they cut the excess bolt threads off. Lift has been rock solid for years, a long 4 post, 14k with air jacks.

 

[kvom]

Thanks. The lift vendor (GregSmithEquipment.com) strongly suggest not mounting on peers. The deal is that the vendor wants the mounting bolts to be drilled thought the foundation. That way if the lift has to be moved (concrete cracks or you move) the bolts can be driven into the ground beneath the slab and the lift doesn't need to lifted up off the bolts.

Seems to me that the holes can be drilled through the pier, even if it's thicker than the length of the bolts. Or even just drill deeper than the length of the bolt.

 

[Muttly]

Seems to me that the holes can be drilled through the pier, even if it's thicker than the length of the bolts. Or even just drill deeper than the length of the bolt.

Drilling thru the floor as the manufacture recommends or drilling extra deep to be able to over drive an abandoned anchor makes sense, but most sleeve anchors are not designed, tested, or rated for this application, and should be installed in a hole drilled to the depth specified by the manufacture.

not a big deal in your own garage, but remember who's responsable when anchors fail in an install that is not to spec.