radiant heat/new floor over old?

[scotty t]

i'm tying to resurrect a poorly built garage by starting at the bottom. the original floor is probably as much as a foot thick in some areas, it has no cracks but it is not even remotely level or flat! the garage has a tall foundation wall (about 2' above slab) and a "floating slab" inside. my concrete guy says "no problem" he can pour on top of it with a barrier to separate the two slabs. i would like to run tubing for radiant heat in the new slab. my concern is insulation. i don't have head room for a bunch of foam between the two slabs. also what about between the slab and the foundation walls? the more i read about bubble wrap under the slab the less i believe in it. I've researched a fair amount but i haven't seen this senario. thanks for any input.
Scotty T

 

[sands35]

Uh - foam? 1" is better than nothing and will give you something to staple PEX tube too.

If you have a 2' wall, then 2" of foam and 4" of concrete shouldn't be a problem. You'll need to think about how cars and people will get in and out though. Where are the doors (car and man door)?

If the current slab is really floating, then it's a day's job (maybe two) to break it up and take it away. Then you can do a proper job of it.

 

[OldNeons]

Tear it out and do it right. Otherwise, you will regret it.

 

[scotty t]

i agree tear out would be the way to go but i don't have the time,$$ or enthusiasm for it! the heated floor was an after thought, when the concrete guy said he wanted to use a barrier i thought of the bubble wrap stuff. then after some research it didn't sound like the stuff to use.the ceiling height isn't critical but i'm already going to raise the ceiling for clearance for a car lift. the garage door is going to be raised as well, the man door is high enough. is 1" of insulation enough? i don't want to do the heated floor half assed, i already have a hanging furnace i can use.

 

[sands35]

Rent a big breaker and a dumpster. Hire some day labor for $100 a head (if you want) or bring over some buddies (that will just cost you some beer and pizza) and it will be done in two days. Small price to pay for a properly done job.

2 days for the rest of your home ownership? Easy payback. 1/2 way is not pulling out the floor. It will look funny on re-sale and never be "right".

A mini-excavator with a breaker would be $500 for day (or so) and probably get 80% of it done in a few hours. A hand held is probably $70-100 a day.

Just make sure your family isn't in the house - it's friggin' loud!

Raising the ceiling might cost more than pulling out the floor.

1" is better than nothing. In my area that is the code minimum (St. Joe - ~30 min north of South Bend). 2" seams to be "standard".

 

[OldNeons]

I have done things the "easy" way when I didn't have the "time, $, or enthusiasm" and regretted it ever since. Rent a skidsteer with a breaker and pallet forks - probably about $250 for the weekend. It won't take you a full day. With a machine you really don't even need anyone to help other than to haul the waste off. Rent a dump trailer and haul to the nearest concrete recycling facility if available (often cheaper than THE DUMP). Or find a farmer who needs some drainage ditches filled in for free I assure you, you will be much happier in the end to have a nice level floor that you know will be solid and problem free and have a good heating system. If your floor below has cracks or moves - your new floor above will have the same ones - and fracture your radiant tubing in the process.

 

[scotty t]

Rent a big breaker and a dumpster. Hire some day labor for $100 a head (if you want) or bring over some buddies (that will just cost you some beer and pizza) and it will be done in two days. Small price to pay for a properly done job.

A mini-excavator with a breaker would be $500 for day (or so) and probably get 80% of it done in a few hours.

Just make sure your family isn't in the house - it's friggin' loud!

Raising the ceiling might cost more than pulling out the floor.

1" is better than nothing. In my area that is the code minimum. 2" seams to be "standard".

easier said than done! tear out is not an option considering to resources i'm willing to commit. the raised ceiling is practically free. i'm just raising the wall ties(joists) 2'. this is just a 24x24 on the back of my property, not my main shop. i just want it to be dry and a good place for a lift to store some of my cars.

 

[scotty t]

i really appreciate the replies, but i don't want to make it into as big of job as some of you think i should. i'm just not willing to commit the time, labor and money to do a tear out. this is my "spare" garage not an attached garage. the concrete guy says no problem on the new slab over old slab issue considering there are no cracks. the heated floor idea might just be more of pain than it's worth though.

 

[Highbeam]

My current house has a converted attached garage. Garage built the same way as yours which is a floating slab inside a stem wall. They just carpeted over the sloped slab and called it a room. I went in and removed the carpet, attached 2" foam around the edges, layed 6 mill poly VB, and then went around with my laser level and marked on the floor the thickness of foam that I could put in while still maintaining 3" minimum of concrete. This room would remain residential interior so no cars. Some places was no foam and some places I used 2" of foam. I put in the foam in and then layed mesh over it. We poured mud and burned it with a steel trowel, sealed it 6 months later. Looks GREAT. I did not add pex tubes but it would have been done before the mesh.

A little foam underneath is better than none. Edge foam is most important.

 

[jvitez]

With your parameters I'd pour over top as you're planning, and use a radiant tube heater for heat. Much cheaper and easier for your application, though heat loss through the slab will be same with either method.

 

[scotty t]

With your parameters I'd pour over top as you're planning, and use a radiant tube heater for heat. Much cheaper and easier for your application, though heat loss through the slab will be same with either method.

i think i'll research the radiant tube heater, thanks

 

[BadgerBoilerMN]

Hydronic radiant ceiling. Insulate the perimeter.

 

[CARS]

Hydronic radiant ceiling. Insulate the perimeter.

Does that really work? I have heard of ceiling and wall installs in Europe before (I think it was all copper/iron though).

 

[BadgerBoilerMN]

Every day.

There are many thousands of homes in the US with radiant ceiling heat. Most were formed on a bench with soft copper tubing, raised to the ceiling, fastened and plastered over all.

The only thing better it a radiant wall or floor.

I would send you a picture but GJ can't handle the pixels.