Concrete Patio Built On Dirt???

Builder · May 24, 2006

( They pour it right on top of the ground here in Az all the time. But we really do not have any grass or top soil so they are pouring ring on top of hard packed desert which is almost as hard as concrete and the mositure level is probably close to zero. )

And most importantly, you have no frost.

Big difference. /forums/images/graemlins/wink.gif

Builder · May 24, 2006

( They pour it right on top of the ground here in Az all the time. But we really do not have any grass or top soil so they are pouring ring on top of hard packed desert which is almost as hard as concrete and the mositure level is probably close to zero. )

And most importantly, you have no frost.

Big difference. /forums/images/graemlins/wink.gif

PILOON · May 24, 2006

Topsoil and any vegitation should be remouved otherwise it will decay and sink eventually.

If you have frost, any large stones need remouving down to frost level otherwise the slab will eventually heave.

Rebar around the perimeters is also needed and 6" X 6" heavy wire mesh in the entire slab otherwise you will have cracks. (a rebar grid is also OK)

Sure a gravel or sand base is more desirable but depending on the conditions not essential other than perhaps drainage considerations. Prime function would be otherwise for compaction.

On the other hand I have poured at times slabs on virgin soil without problems.

PILOON · May 24, 2006

Topsoil and any vegitation should be remouved otherwise it will decay and sink eventually.

If you have frost, any large stones need remouving down to frost level otherwise the slab will eventually heave.

Rebar around the perimeters is also needed and 6" X 6" heavy wire mesh in the entire slab otherwise you will have cracks. (a rebar grid is also OK)

Sure a gravel or sand base is more desirable but depending on the conditions not essential other than perhaps drainage considerations. Prime function would be otherwise for compaction.

On the other hand I have poured at times slabs on virgin soil without problems.

JohnSinVA · May 25, 2006

One poster said:

"They are putting your patio on topsoil, which is not only useful around the house but contains organic materials that will decompose and settle."

Methinks you don't know the soil conditions of Loudoun Co., VA very well. When the concrete guy says the water will just lay in the gravel he isn't kidding. I had a poured patio done in the "traditional" way with concrete on top of gravel. After installation I began digging out for flower beds following a couple days rain. Breaking the soil/gravel border unleashed a flow of water that lasted quite some time. I have no doubt that had I done nothing that patio would have broken into several large chunks in two winters' time. I insisted on gravel under the concrete also, after the contractor proposed the slab on ground.

Mike - the contractor is willing to stand behind his work for 3 years. That's a pretty good indicator he's confident in his methods and is aware of the soil conditions that are predominant in the area. If it's going to get damage from frost heave, it's going to happen in that warranty window.

JohnSinVA · May 25, 2006

One poster said:

"They are putting your patio on topsoil, which is not only useful around the house but contains organic materials that will decompose and settle."

Methinks you don't know the soil conditions of Loudoun Co., VA very well. When the concrete guy says the water will just lay in the gravel he isn't kidding. I had a poured patio done in the "traditional" way with concrete on top of gravel. After installation I began digging out for flower beds following a couple days rain. Breaking the soil/gravel border unleashed a flow of water that lasted quite some time. I have no doubt that had I done nothing that patio would have broken into several large chunks in two winters' time. I insisted on gravel under the concrete also, after the contractor proposed the slab on ground.

Mike - the contractor is willing to stand behind his work for 3 years. That's a pretty good indicator he's confident in his methods and is aware of the soil conditions that are predominant in the area. If it's going to get damage from frost heave, it's going to happen in that warranty window.

EddieWalker · May 25, 2006

( - the contractor is willing to stand behind his work for 3 years. That's a pretty good indicator he's confident in his methods and is aware of the soil conditions that are predominant in the area. If it's going to get damage from frost heave, it's going to happen in that warranty window. )

Three years is an eternity for some people, especially contractors. Just because he says he'll fix or replace it if it cracks, what gantantee do you have that he will still be around? So many come and go that it's hard to keep them there long enough to finish the job.

I wouldn't give any credence to a garantee, but rely more on technique and refrences. Lots of people give garantees without any plans to honor them. It's real easy to offer one, but getting them to answer the phone or show up is a whole different story.

I don't have much for topsoil here, and it does't get cold enough for a freeze to be much of a factor in anything. We almost always just scrape off the vegitation and pour right on the clay.

I've even seen parking lots blacktoped over the clay. This shoocked me, but several years later, and it's still fine, plus I see it being done all the time too, so anything is possilble. /forums/images/graemlins/confused.gif

In your situation, I agree with the others and think you should insist on them building it the way you agreed upon from the beginning. If not, you might want to cancel the project and start looking for another contractor.

Eddie

EddieWalker · May 25, 2006

( - the contractor is willing to stand behind his work for 3 years. That's a pretty good indicator he's confident in his methods and is aware of the soil conditions that are predominant in the area. If it's going to get damage from frost heave, it's going to happen in that warranty window. )

Three years is an eternity for some people, especially contractors. Just because he says he'll fix or replace it if it cracks, what gantantee do you have that he will still be around? So many come and go that it's hard to keep them there long enough to finish the job.

I wouldn't give any credence to a garantee, but rely more on technique and refrences. Lots of people give garantees without any plans to honor them. It's real easy to offer one, but getting them to answer the phone or show up is a whole different story.

I don't have much for topsoil here, and it does't get cold enough for a freeze to be much of a factor in anything. We almost always just scrape off the vegitation and pour right on the clay.

I've even seen parking lots blacktoped over the clay. This shoocked me, but several years later, and it's still fine, plus I see it being done all the time too, so anything is possilble. /forums/images/graemlins/confused.gif

In your situation, I agree with the others and think you should insist on them building it the way you agreed upon from the beginning. If not, you might want to cancel the project and start looking for another contractor.

Eddie

HappyCPE · May 25, 2006

You're right, I don't know Loudon County. But when I bid on a segment of the underground people mover at nearby Dulles Airport a few years ago, the drawings and specifications were very comprehensive about subgrade preperation prior to paving. They included removing topsoil and including engineered crushed stone.

A warantee is only as good as the person who gives it. Based on the fact the contractor claimed he always did it that way, I'd say his word is worthless. I would be very nervous about having this guy work unsupervised; if it were my place he'd be thrown off the farm. At a minimum his work should be inspected and measured every step of the way.

HappyCPE · May 25, 2006

You're right, I don't know Loudon County. But when I bid on a segment of the underground people mover at nearby Dulles Airport a few years ago, the drawings and specifications were very comprehensive about subgrade preperation prior to paving. They included removing topsoil and including engineered crushed stone.

A warantee is only as good as the person who gives it. Based on the fact the contractor claimed he always did it that way, I'd say his word is worthless. I would be very nervous about having this guy work unsupervised; if it were my place he'd be thrown off the farm. At a minimum his work should be inspected and measured every step of the way.