Insulated Floors....anybody have one?

[67restoproj]

I am considering insulating the floor in my shop. It will be a 26x30 slab 4-5 in thick. Worried about the foam compressing due to weight. Anyone have experience in this? Looking for pros and cons....thanks in advance.



Link to shop http://www.garagejournal.com/forum/showthread.php?t=16636

 

[carcruse]

I put the foam sheets in around the edges 2 feet in. You don't really need to do the entire floor area. They make special foam sheets for this. If I remember correctly, the ones found at places like home Depot, Lowes, etc. are 125 psi and the ones you should handle 250 psi.

you can see them under the vapor barrier in this picture.

 

[Ezzie]

You might want to consider door cutouts if there are any steel entrance door manufacturers in your area. It is a scrap product so inexpensive and quite durable.

 

[ScaldedDog]

The stuff you find at HD and Lowe's is 25psi. I went with the Dow Hi-Load 40psi product, but it's almost twice as expensive ($20 for a 2'x8' sheet).

Concrete turns out not to be that heavy: 1 cubic yard is about 4000lbs, or 0.0857lbs per cubic inch, so a 6 inch floor only weighs 0.5lb psi.

Vehicles are another matter. My Excursion weighs 8000lbs, and has a roughly 50 square inch contact patch. That's 40psi at the surface, though that gets dissipated by the concrete and rebar. It is why I went with the Hi-Load stuff, though.

Can't say how well it worked, as the concrete has only been down 2 days.

Mark

 

[carcruse]

Scaldeddog is right, it's 25 and 40 psi not 125 and 250. My memory is bad.

 

[thammel]

If you google DOW you'll find that the 2 inch thick styrofoam is rated for use under slabs. It's amazing but it's correct that a 6 inch think slab only exerts 0.5 psi on the foam, so 25 psi is plenty. Yes, the slab is monolithic (unless it totally breaks up!) so even the pressure exerted by your 10000 pound car or truck is insignificant. Let's do some math. Take a small 20 x 20 garage. That's 400 square feet or 400 x 144 square inches which is roughly 57000 sqaure inches Multiply this times 25 and you get a capability of the stryofoam to support over a million pounds (it's exactly 1.44 million!) Sounds pretty good to me!

Tom

 

[ScaldedDog]

...and you get a capability of the stryofoam to support over a million pounds (it's exactly 1.44 million!) Sounds pretty good to me!

Tom

And yet, lots of folks have garage floors that settle...

Tom's right, though I felt a lot more comfortable with the 40psi stuff. Stinking difficult to replace it...

Mark

 

[rburke65]

Wouldn't the cause of the floor settling be attributed to the base being incorrectly installed and not to the styrofoam?

 

[Burl]

Your compacted stone should also help against the settlement.

 

[GSSFC]

You could also consider having spray foam installed 2" of 2# pound foam would provide you a monolithic insulated surface as well as contour to the variations in the base that would make installation of sheet foam uneven.

Tim

 

[GSSFC]

Wouldn't the cause of the floor settling be attributed to the base being incorrectly installed and not to the styrofoam?

I just walked a jobsite last week that the contractor has sand as a base in the basement and then blue dow foam on top. The base had to be extremely uneven because there were all sorts of highs and lows and you could feel the foam move underfoot. That sort of installation is bound to cause problems with the concrete floor down the road. I consider both the site contractor and insulation contractor to be at fault. I would never install a product on a poorly prepped surface.

Tim