Driveway - pour concrete over granite curb?

homeowner54 · 06-09-2010, 07:10 PM

Hi -- I'm getting bids on a driveway apron repair. There's an existing granite curb at the foot of our driveway, below the level of the asphalt on the street, and below the level where the old driveway starts.

An engineer from the city told us we should remove the granite curb before pouring the concrete, but the contractor we're leaning toward using wants to leave it in place.

City code requires a step up of an inch or so from the pavement, so the concrete could be poured on top of the curb at a thickness that would meet code.

Is there some incompatibility between the materials in concrete vs. granite that would cause the concrete not to bond and therefore be less stable? Or would we be fine letting the contractor pour concrete on top of that granite curb?

Thanks.

Wildie · 06-09-2010, 07:50 PM

You never posted where you live, but if it freezes there, it won't be long before the concrete that is laying on the granite will break away!
I would follow the engineers advice!

Bondo · 06-09-2010, 09:31 PM

Ayuh,... I Agree, it'll Break off in no time...

concretemasonry · 06-09-2010, 09:55 PM

That curb is probably on city property, so listen to the city engineer/inspector. Get rid of the granite.

The granite is probably on a soil base oir a thin, weak concrete bed. Since the granite curd can accept movement, this is O.K. for a "flexible" wall/curb. Putting a rigid pavement on a flexible surface is never good because of cracking. I am sure the city engineer has seen this before and is speaking from local experience and methods.

It is not a compatibility of the individual materials, but one (the granits curbs from individual units) is really flexible, while poured concrete is rigid.

I lived in a city where no reinforcement (rebar or wire) was permitted in the concrete on aprons or sidewalks because of problems with removal and maintaining the utilities under it. I even had to sign off on using fibers in the concrete. - The rock was 3-4' down and the frost depth was 4', so location is more important than you think from your own local perspective.

Dick

homeowner54 · 06-09-2010, 11:10 PM

Thanks, all, for the feedback. We will definitely have those granite curb sections removed. I got the same opinion this evening from a mechanical engineer friend who lives in the neighborhood.

I've got a couple of reasonable bids from reputable contractors who are willing to include that in the job, so looks like we're making progress.

Appreciate your help and the quick responses!

06-09-2010, 07:10 PM	#1
homeowner54 Newbie Join Date: Jun 2010 Posts: 2	Driveway - pour concrete over granite curb? Hi -- I'm getting bids on a driveway apron repair. There's an existing granite curb at the foot of our driveway, below the level of the asphalt on the street, and below the level where the old driveway starts. An engineer from the city told us we should remove the granite curb before pouring the concrete, but the contractor we're leaning toward using wants to leave it in place. City code requires a step up of an inch or so from the pavement, so the concrete could be poured on top of the curb at a thickness that would meet code. Is there some incompatibility between the materials in concrete vs. granite that would cause the concrete not to bond and therefore be less stable? Or would we be fine letting the contractor pour concrete on top of that granite curb? Thanks. Last edited by homeowner54; 06-09-2010 at 07:10 PM. Reason: grammar

06-09-2010, 07:50 PM	#2
Wildie Member Join Date: Jul 2008 Location: Canada (s/w ON.) Posts: 2,294	Driveway - pour concrete over granite curb? You never posted where you live, but if it freezes there, it won't be long before the concrete that is laying on the granite will break away! I would follow the engineers advice!

06-09-2010, 09:31 PM	#3
Bondo Master General ReEngineer Join Date: Dec 2007 Location: Chaumont River, Ny. Posts: 3,175	Driveway - pour concrete over granite curb? Ayuh,... I Agree, it'll Break off in no time...

06-09-2010, 09:55 PM	#4
concretemasonry Member Join Date: Oct 2006 Location: Minneapolis/St. Paul, Minnesota - Latitude 45.057 Longitude -93.074 Posts: 3,357	Driveway - pour concrete over granite curb? That curb is probably on city property, so listen to the city engineer/inspector. Get rid of the granite. The granite is probably on a soil base oir a thin, weak concrete bed. Since the granite curd can accept movement, this is O.K. for a "flexible" wall/curb. Putting a rigid pavement on a flexible surface is never good because of cracking. I am sure the city engineer has seen this before and is speaking from local experience and methods. It is not a compatibility of the individual materials, but one (the granits curbs from individual units) is really flexible, while poured concrete is rigid. I lived in a city where no reinforcement (rebar or wire) was permitted in the concrete on aprons or sidewalks because of problems with removal and maintaining the utilities under it. I even had to sign off on using fibers in the concrete. - The rock was 3-4' down and the frost depth was 4', so location is more important than you think from your own local perspective. Dick

06-09-2010, 11:10 PM	#5
homeowner54 Newbie Join Date: Jun 2010 Posts: 2	Driveway - pour concrete over granite curb? Thanks, all, for the feedback. We will definitely have those granite curb sections removed. I got the same opinion this evening from a mechanical engineer friend who lives in the neighborhood. I've got a couple of reasonable bids from reputable contractors who are willing to include that in the job, so looks like we're making progress. Appreciate your help and the quick responses!

Driveway - pour concrete over granite curb?