Concrete over concrete

[Bomber Frank]

Some history, my shop caught fire earlier this year, coverage denied. Long story, but need to move on.
So, my old shop was basically a pole barn (36' x 60') with an interior area of 24' x 40' that was heated.
I am planning on replacing the building with a 24' x 40' garage that matches my house better.
I want to use a monolithic slab this time around and I will be installing floor heat.
So here's the question:
What are the thoughts on pouring the new slab over the existing concrete floor? I would need to cut the floor around the perimeter and remove the concrete in order to get the right depth around the edges and place rebar in these areas. I would lay rigid insulation board over the old floor, and then add the new floor on top of this.
The old floor never moved, never cracked and is solid. The floor was poured 15 years ago. I just think that this is a solid base, and don't want to rip it out and dispose of the concrete if I don't have to.
Did I explain this well enough?
Let me know what your thoughts are....thanks.

 

[tlmartin84]

Why pour a new floor if this one is intact?

Why not build the building around the existing slab?

 

[Bomber Frank]

To answer above, I want to get away from the pole barn type structure.
The existing slab is not structural, it was just the floor inside the heated part of the building.
My understanding on the monolithic slab was that it was to all be tied together.
And to be honest, by pouring over, I would be able to gain about 6" in vertical height which would help with drainage.
I've been kicking various things around for about a month now, it seems the more I think about it, the more confused I get.

 

[willymakeit]

Do a mono with the turndowns past the existing slab. No different than calling the existing slab a mud slab. Put a vapor barrier between them so they don't bond together.

 

[Zeke]

Do a mono with the turndowns past the existing slab. No different than calling the existing slab a mud slab. Put a vapor barrier between them so they don't bond together.

I like that answer. I was wondering about the insulation board between the slabs.

 

[C96]

Do a mono with the turndowns past the existing slab. No different than calling the existing slab a mud slab. Put a vapor barrier between them so they don't bond together.

I agree also, good answer.

Quote:
Originally Posted by James-W

I brainwashed a woman once, I stomped on her douchbag.

____________________________________________________________________________________________________________

Zeke, every time I see a post of yours with the James-W quote, I laugh my *** off!

 

[Bomber Frank]

Thanks for the input.
I thought along the same lines as Zeek, but had several different opinions.

 

[tlmartin84]

I concur with all of the above.

My thought was if you wanted to save yourself some money, you could just pour footers, form up some walls, attach expansion to the edges of the existing slab and pour the walls right up to the floor.

The concrete would fill any edge voids created when digging the foundation. The wall and footing would make an L shape which is perfectly acceptable with the right reinforcement.

 

[AP514]

if you are going to pour on top just shave /rough up existing slab..use some concrete milk and then pour new crete on top..if less than 3 " just add fiber additive in the crete mix no rebar needed.

 

[D.J.]

OK I'll be the nosetty SOB, why was coverage denied? Just wandering as I'm in the fire service!
THanks D.J.

 

[willymakeit]

I like that answer. I was wondering about the insulation board between the slabs.

Its not a problem. Anything to keep them separated. Thought is to allow them to move a little independently of each other.
We do it on large footings a lot. By large think 20'X30'X10'.

 

[ACDNate]

Its not a problem. Anything to keep them separated. Thought is to allow them to move a little independently of each other.
We do it on large footings a lot. By large think 20'X30'X10'.

Sweet Baby Jesus! a 20'x30'x10" footer? What kind of building is going on that?

 

[bad_idea]

Here is a thought. The cost of pouring a fresh slab vs pouring over the old one can't be too much different. Perhaps move the building back to use the existing slab as a large parking area in front of the new shop?

 

[Bomber Frank]

D.J., coverage was denied due to misrepresentation. Seems the broker didn't let the insurance company know about a woodstove.
Bad Idea, already doing this. Moving back 20' already to have some concrete parking area.

 

[Scott H in Wheaton]

I like your idea of using the existing slab as a base and I understand adding the insulation and the floor heat. I used to paint cars in a building with radiant floors and it was sweet!

Given the chance I would do what you are doing.

 

[willymakeit]

Crazy engineering. Used on a elevator shaft [6 stories] and one for each stair tower [2].Then cast in place shafts and towers with gang forms.
They called it moment of turnover ,tho I've never seen a 6 story building turnover.
See this kind of footings on water towers ect. Concrete suppliers love you.
2/3 pump trucks with 2 trucks at each pump delivering concrete. Have had over a 100 yds in trucks lined up to deliver as much as they can quickly. Keeps the testing engineers hopping to.

 

[D.J.]

Bomber Frank sorry about your bad luck maybe a learning experience for newcomers to the site, also a plus for a standalone detached wood burner or pellet stove for radiant.