Remove old garage pad or pour over top?

[CadMan60]

I'm finally getting around to building the new garage and knocked down the old one last week. The old pad is in poor shape and my plan was to remove it. The guy that is building the new garage says it doesn't need to come out. (cost to remove would be $700-800 plus dump fees, which could be another $700-800, so say $1500 in total to remove). The current pad is in poor shape, heaved in places and has short crib walls around it - not to mention that it is not in exactly the right spot so at least part of the old pad would need to come out or it would be extending out past the new pad.

Any thoughts on this? Does this sound bush league to you? Seems to me the concrete guy should want to start fresh with proper rebar and thickness of the new pad and not just be laying part of it on top of the old one. He says he'll use it as a base instead of gravel. Any questions I should be asking if that's the way we go. Don't want to incur unnecessary costs, but also don't want to do something half-assed that will crack/heave in the future.

Here's a photo of what we're dealing with.

Thanks for any insights.

 

[Lassen Forge]

You pour over the top of it and you'll end up having issues - the pour was done wrong in the beginning, and where it was failing before is where your brand new pad will continue to go to ****. If you can afford it, have it pulled and start over with a good compacted base and do it right. (Our old garage in town had 3 layers of fubar garage floor pads like that, every layer failed within a matter of years, so I speak from some kowledge.)

Another option - If you really want to keep it for base material, then rent a compressor and pavement breaker, spend a week breaking the old pad into rubble, and use it as part of your base material. IMO that's way more work than its worth, is still about 1/4 assed, but it's better than pouring on top of the fubar pad.

This may sound harsh, but if it were me, once the guy suggested pouring over a blown pad, I'd be looking for another contractor who will do the job right. There are enough of them out there who will; you just have to find them and pay them what they're worth.

 

[southalabama]

One word. Remove

 

[bams50]

I would absolutely be afraid of it causing problems with the new floor. Plus, from experience, I would strongly recommend you put in tubing for in floor heat. Even if you don't intend to use it now, it's easy and fairly cheap to put in, And you may find later that you want it. Also, even if you don't use it, it will be a great selling point should you sell in the future.

Of course, that definitely means you would want to break out the old concrete pad.

 

[NUTTSGT]

I poured over the old pad in my garage but that was a totally different animal that what you have. If that was my pad, I'd remove it and start fresh.

It's an old pad that appears to have some issues. What's the frost depth up there ? I'd hate to find out the old foundation isn't deep enough after you finish the garage and it causes problems the very first winter.

Want to save money, rent a jack hammer and construction dumpster. Invite a few friends over for a cook out or pizza one Saturday. Have them bring the wives and kids, let the kids haul the broken concrete to the dumpster.

 

[pitterpat]

I poured over the old pad in my garage but that was a totally different animal that what you have. If that was my pad, I'd remove it and start fresh.

It's an old pad that appears to have some issues. What's the frost depth up there ? I'd hate to find out the old foundation isn't deep enough after you finish the garage and it causes problems the very first winter.

Want to save money, rent a jack hammer and construction dumpster. Invite a few friends over for a cook out or pizza one Saturday. Have them bring the wives and kids, let the kids haul the broken concrete to the dumpster.

Good idea about the party.

From doing tile work, an old bad substrate ALWAYS telegraphs through. Also, about the contractor, REMOVE them too! that is a horrible idea to pour over a heaved broken pad.

 

[cdestuck]

The cheap always turns out to be expensive

 

[Bigplum]

Could you just break it up and use it as sub base or ******** ? ( English style)

 

[sberry]

What could you possibly pit under a new slab that would be better than that?

 

[kmcphee]

Break up the concrete and use it to build a retaining wall on your property. You will be recycling and saving the dumping fees at the same time. Google "recycled concrete retaining wall" images, you will be surprised at how well it looks. I'm doing a 200' wall right now along one side of the driveway. Pouring over that slab will be nothing but problems!

 

[readhead]

Did this come up during your discussions with the contractor before the job? Was removing the existing slab included in the contract price? If so somebody is trying to make some money by leaving it. If it has been there a long time it might be ok but why take a chance. I presume the new footings and stemwall would be outside this concrete.

 

[reeskm]

Good thing I found this thread. I'm in Calgary too, with the same problem. Now I know exactly what the solution will be! Removal!

I also have a beautiful agregate patio that I have to cut and remove some sections to make way for a double garage.

For someone with no experience with concrete, is it really as simple as renting a jack hammer, a dumpster and concrete saw? Anybody have any more details on how to do some of this myself with friends pitching in for labor?

 

[Rory Bellows]

There is a place 10 minutes from my house that recycles concrete. You can dump it for free! They are a crushing plant. I never would of believed a place exists that takes old concrete for free until I found it.

 

[Zeke]

Good thing I found this thread. I'm in Calgary too, with the same problem. Now I know exactly what the solution will be! Removal!

I also have a beautiful agregate patio that I have to cut and remove some sections to make way for a double garage.

For someone with no experience with concrete, is it really as simple as renting a jack hammer, a dumpster and concrete saw? Anybody have any more details on how to do some of this myself with friends pitching in for labor?

Absolutely the best way to remove concrete is to lift it in sections. It will break on its own or you can help it break with a sledge once one edge is lifted by a big bar, pipe or a bucket on a tractor. Making rubble with a jackhammer is to make a lot of work raking and shoveling. Sometimes there's no choice, but the larger the pieces the faster it goes.

If the recycle plant is too far away for run, watch CL for 'fill wanted'. Also consider using stacked concrete for a retaining wall, terracing, random stone walks or raised planters. It can be rather attractive and many ground covers and plants will grow in the cracks. I know berries will.

 

[sberry]

Why is disturbing this great compaction better?

 

[jlckmj]

If you are going the same size, remove it.

If you are going larger in all directions, I would leave it if you have enough room to put down a monolithic slab. (good deep footings outside the existing slab tied into the new slab with rebar) AND, you can handle the extra 6 inch height.

Jim

 

[Zeke]

Why is disturbing this great compaction better?

I think it's what's under this great compaction. If something is heaving the existing then why not consider what it will do the the new?

Here's the thing, I think all slabs should be thick and uniform in that. Placing a new slab over an old one and extending it in any direction is going to make for a weak spot because at some point the overall thickness is going to change. It may start cracking just outside the 'great compaction'.

OTOH, if the old slab is thin and breaking, maybe drive the concrete truck over it a few times placing the mud over the old last after closing the last form board.

 

[volleyball]

I say just build right over the top of it, Then plan on next year asking how to raise it safely so you can spend 3 times as much fixing it.

 

[metlmunchr]

I'd get rid of the contractor first. His solution is the equivalent of putting 2 gallons of Bondo in a quarter panel rather than straightening or replacing it. Anyone with "solutions" like that will end up giving you a substandard job regardless of how much you ride herd on them. Why? Because that's the only class of work they know how to do.