Removing concrete slab

[grahamsz]

My home builder poured me a nice thick (16") concrete patio (8'x10') which we didn't ask for or pay for. Unfortunately it's squarely in the way of where we want to build a deck and there isn't really clearance above it to get the deck joists in.

I'm still fighting them on trying to get it removed, but they must have the worst customer service department imaginable. The fact that it cracked in half while still under warranty wasn't enough to get them to do anything.

I've called a few concrete contractors and can't even get one to give me a quote.

It's in the back yard and I dont have the gate clearance to get a bobcat or similar through.

As a result it's starting to look like i'll be doing this myself :( . I've never done any concrete work on this kind of scale, although i've got friends who've got some experience with jackhammers and excavation and will work for beer. One suggested that i rent a big hammer drill and drive a grid of holes into the slab which I could then drive a jackhammer into and break apart... is that plausible?

How likely is it that a builder would put rebar into a non-structural patio?

Any other advice?

Graham

[SQLit]

Rent a air powered 75 or 90 pound jackhammer. Make damn sure your neighbors are up before you start. You will be done in a couple of days, based on

16" thick. Then comes the fun of removing the chunks. Using your measurements you have about 4 yards of concrete, weighs about 8000 pounds, give or take. I would have a roll off delivered and put the concrete in that. Last one I got was $200 bucks. Beat the hell out of driving to the dump with my pickup. Better ask before you rent, they may have weight registrations.

As for reinforcement? I do not know where you live. Where I live footings for the posts are 16' deep and yes they have rebar in them. We do not pour slabs that thick.

Personally I would be considering flagstone or tile instead. Please do not call me the weekend your planning on making a LOT of racket.>>>>>

[grahamsz]

Thanks for the advice.

I've been quoted $325 for a roll-off if i'm filling it with concrete - i might be able to find cheaper since i'm only about a mile from a landfill.

It appears to be an on grade slab. I dont think it has any footings, i'll do some digging this weekend and confirm that.

I'm just glad it's not my front porch, that thing is about 12'x6' and about 5' thick, it is structural and has footings below that!

I suspect the grade around the house has a lot to do with how thick these things are.

I will need to backfill around the house to meet the engineered drainage requirements. Is there anything stopping me using concrete rubble as part of the fill? It seems very excessive to have to wheelbarrow the concrete out and then move fill dirt in to replace it.

Graham

[BobK207]

Graham-

SQLit's advice is sound but his weight calc is off.

You've got 8 tons (16,000lbs) of concrete, in SoCal that's nearly a full lowboy rolloff (17,000)

"One suggested that i rent a big hammer drill and drive a grid of holes into the slab which I could then drive a jackhammer into and break apart... is that plausible?"

In my concrete demo experience, no this will not work. It's a very good way to get the jack hammer tool stuck. You've got the attack this things from the outer edge (about ~8 to 10 inches in)

Unreinforced concrete fails when subjected to tensile stress. I would suggest digging the slab free along one edge so that the slab can "break to a free edge".

This beast is so thick it will be a lot of effort.

You might consider a BobCat with breaking hammer on it, it will make short work of this.

cheers Bob

[buffalobill]

uh, why not build on top of it? or astroturf it and let summer get started.

[Art]

Are you sure it is really 16 inches thick? Maybe just at the edges?

[grahamsz]

How would I know?

Is there some standard way to test that.

Graham

[grahamsz]

Well we'd like to put in a 350 sq ft deck and since the slab is within an inch or two of the interior floor it doesn't allow us to put joists over the top of it.

I'm pretty sure that code prevents us from actually fastening the deck support to the slab (as it's not structural).

The only other option (that I can see) would be to nail 2x4's flat onto the slab and lay the decking boards on the 2x4's. The rest of the deck support would end up being freestanding on concrete piers and perhaps attached to the house in a few places. Unfortunately since the slab is split clean in two, i'm worried that it could move apart and warp the deck.

Graham

[grahamsz]

Thanks for the advice.

I'd though it'd be about 8 tons also. The hauler i spoke to required that we rent a full size rolloff if we are doing anything concrete so that's probably ok.

The slab is free on two sides and buts against the foundation on two - it shouldn't be hard to figure out where to start.

How wide are bobcats... i think we only have 32" clearance on our gate and i could perhaps get 40 if i tore out a couple of fence posts.

Graham

[buffalobill]

here are some points to ponder: what is the frost line in your city. if any? what is the depth for foundations and footers required for your town? you need this info for your deck footers. the builder may have put in a 16" foundation with only a 4" slab, or whatever is locally required. ask your permit office what was required and what do the building plans or blueprints show may be similar to what you have. what does your survey show? who/what/where/when/why/how?

[grahamsz]

Thanks for the advice!

The slab is about 12-14 inches above grade and feels like it averages only 4 inches below it. I'm shooting at 16 as a typical depth, although i really haven't done enough excavation to know that for sure.

I didn't think it was structural and doesn't appear to have piers under it (like my front porch does) although, again, i've only done a cursory check for such things.

We're just outside of boulder colorado and for foundations i'm pretty sure that the frost line requires that foundations be 32" below grade.

Graham

[kevin]

Could it really be 16 inches thick? That seems awfully thick for just a patio. Anyone know what that would support, weight wise?

I have looked at putting in a garage slab, an 4, 5, or 6 inches is normal around here. 16 would be rediculous.

I don't know what this thing looks like, but might it just be a floating edge-thinkened slab? They would have mounded up dirt and fill in a rough shape of the patio, then poured concrete on it to make a 4 inch layer on top, and about 8 inches or so on the sides.

But it seems like the buildter really needs to take care of this. Small claims court might help, perhaps? And lifting 8tons of anything by hand is no fun. I did a few tons of dirt by hand last summer, over the course of several weeks. The payoff was a nice garden for my wife. Your payoff will be a nice hole where once there was brand new patio. If you really have to do this yourself, wouldn't it be worth it to take down the fence and get a bobcat in there? (At least, I've been looking for an excuse to rent one, and your situation seems like a great excuse).

-Kevin

[hallerb]

concrete costs money wonder why the builder put it there? I guess you consider small claims court against the builder.

if you had room a backhoe would do that job a lot easier.

to find the thickness drill with a masonary bit or preferably rotary hammer drill in a few places

[raven]

Well, the crack, that's a problem, but I would never remove a patio to install a deck. Still...

I find it amazingly unlikely that it's 16" all the way through: it's would almost certainly be only that thick on the edges and substantially thinner at the center.

Still breaking this thing up would be an amazing PITA. Don't go the jackhammer route that tpeople are suggesting: that should be your last resort. Instead go with an expansive demolition agent.

It's a special sort of expanding concrete that you pour into hole strategicaly drilled into what you want to break apart. As it sets, it expands and the force quietly breaks whatever you've got.

But I'd keep the slab.

Either lay sleepers on the slab to support the deck, as you suggested elsewhere, or build your deck around the slab, maybe 9" down so as make the deck a step if the grade if the site warrants such a thing.

After drilling the holes, pour in the expansive mixture and then drink the beer while waiting for the thing to break up.

Hard to say, but I rather doubt it.

Yeah. concrete is wonderfull stuff: don't get rid of it.

Good luck with whatever you decide to do.

John

[BocesLib]

I would doubt that its 16" thick. Thats almost enought to land a plane on. I would think the footers are 16" and the slap itself is only 4" or 5"

Most if not all builders would not spend the extra money on the extra concrete for no good reason.

If you are really pissed at the builders, get a

20 pound sledge hammer and see if you can start to break up the edges. Its a good workout.

[grahamsz]

The builder probably has about 50 truckloads of concrete coming into the subdivision each day, i wouldn't be too surprised if that's a fairly constant number and if they have excess the pretty much just need to dump it.

My front porch is 5 foot deep in places and it's definitely not got dirt piled up in there, though it may have some voiding material.

Good point on drilling holes though - i'll need to buy a longer masonary bit first though.

Graham

[grahamsz]

I think this suggestion wins, anything that moves the beer drinking up in the schedule.

The question remains where do I buy this stuff. I've never seen it on sale and none of the websites seem to be selling it.

I also imagine i'd have to do this is pieces starting from the sides that dont touch the foundation. I dont like the idea of those kind of forces being misdirected.

Graham

[grahamsz]

I may need to go to the small claims court.

The builder (DR Horton Melody) is doing everything in their power to avoid spending money. I've spent hours arguing with them and had to get my towns planning department involved just to get them to meet building codes. And they are still holding out on putting a railling all the way around my 5ft high porch.

Getting them to honor their warranty document seems like a pipe dream :(

Graham

[Edwin Pawlowski]

Forget the deck. Extend the patio. Over the years, you'll be much happier as you have less maintenance, no staining, easy clean up, no rot. .

[grahamsz]

The height is pretty much forced by the grade, but it's entirely possible that there's a mound of dirt under it.

I'm not so phased by the 8 tons. I moved about 3 tons of topsoil last week in an evening and have moved 5 tons of stone over the course of a few weeks before. With a few helpers it could be over pretty quick.

DR Horton just agreed to come out and "take more photos" of the crack. I'm not sure what that'll prove but hopefully they'll fix their mistake.

Graham