Advice Requested For Safely Demolishing Concrete Patio

You should be okay jackhammering fairly close to the foundation. I'd say about a foot and knock the rest loose with a sledgehammer.

As far as the support goes, my recommendation would be to place temporary supports on either side of it before you jackhammer anything. Remove the support, jackhammer a hole, dig it out, pour a footing, (not in contact with the concrete around it), and replace the original support. Then you can safely remove the rest of the concrete after removing the temporaries.

My only advice is to be sure the beam is sitting on/in more than 4 inches of concrete.

If there's no 16x16" footing, I'd shore the 2nd floor up well, too.

Saw cut around the post and all around the patio as close to the house as you can cut. This will de-couple the jack hammer energy from the post and house, and keep it in the patio.

This is a non-expert OPINION.

Good luck.

Hard to tell. I would dig the ground around the supporting posts to see if they have support under the slab. They probably do since the extreme corner of the slab is a weak point and subject to all the weight from the deck above. That would crack if there was no support under.

Patio decks are poured independent of the house foundation or at least if it was done right by the builder, but don't know that for certain; it shouldn't be attached to the foundation. Again, if you dig around at the edge, you can see if it is independent of the foundation or attached.

What does your local building code say about the frost line?

How thick is the slab? What are measurements? I would use a cut saw with diamond blade to cut around the support beam and also to free the slab from the house slab, if it's attached(to kill vibration),and cut the patio into manageable sections, or at least score the concrete deep enough, to break it with a sledge hammer,....The support beam should be on a footer, roughly 24" cube...A jackhammer is a hard way to go, it's better for asphalt roadway then concrete...I've done this many times...

Maybe you should ask this guy how to use one of these saws.

I was using these before he was born....never tried it naked though..

love the later!

The patio is about 190 square feet. Measurements are roughly 16 x 12 feet. I will also be removing another patio about 350 square feet that is without issues. Are you saying that I should use a cut saw (walk behind or handheld) instead of a jackhammer? Would removing about 550 square feet of concrete patio slab be easier with a saw? Seems so to me. Thank so much.

Yes much easier, and much faster....I would use a backhoe and rental dumpster to remove the waste....but you can go smaller, it just takes more time, and more physical work....I would go with the hand held and a 14" blade, you can go smaller it will be slower though....assuming this is a 4-6" slab...8lb sledge should be fine...You might find someone locally looking for clean fill and arrange free disposal....

Another good reason for using a chop saw is in case the two slabs are tied together with rod. I have seen this done when extending slabs.

If you rent a concrete cutting saw make sure it is a wheeled "walk behind" type that allows you to hook up a garden hose to it. You will need the water sprayed on both the circular diamond cutting blade and the old concrete. This is a must have, otherwise you will be ruining the blade in short time; diamond blades are very expensive, and if it is rental equipment most times the Owner will require you to pony up and pay for a replacement blade!

WARNING: Unless you are very much experienced in using a hand-held gas-powered concrete cutting saw don't do it. The saw can meander all over the place and even kick-back on you, possibly resulting in traumatic injuries. I've seen it happen too many times on a project site with both greenhorns and experienced construction workers. All it takes is a little inattention and one quick slip-up and you can loose some toes or even you entire foot. Whatever you do, wear good quality construction boots with steel toe protection built-in.

If you need to cut the old steel rebar or welded wire mess reinforcement (most likely) use a long handled bolt (for leverage) cutter....much cheaper to go this route if you buy it outright or rent it in lieu of buying or renting a power saw.

Total square footage of the deck: Needs to be bigger
Height above the ground: I would't want to fall off; I should probably install a rail
Dimensions of the column: 3-1/2" X 3-1/3"
Columns are made of wood; there are two of these
Contributing area of the deck supported by the lone column: About half
Deck framing is arranged East to West, mostly
Soil type is dry, light brown (unless it just rained)
Groundwater is present on top the concrete patio slab when it rains

Does this help?

AP #1: one of the usual jokesters, Eerrrrrr I meant one of the regular cast of characters.

To be expected, fur sure fur sure...

You can't consider it a "deck", meaning a space for foot traffic, with no safety rail. Instead consider it an invitation for disaster. At once remove any easy access except for visiting birds.

The comments of the structural PE were right on. This is no project for economizing or DIY.

Lou Bindner

I agree entirely. I didn't respond myself because I don't have a great deal of experience at this type of work, but if you hadn't voiced it, I would have had to, albeit with less authority here.

Robbie, I forgot to mention earlier that posting a photo or two of the existing conditions would go a long way solving your questions....

If you are using a person operated jackhammer (electric or air) and begin at the perimeter of the patio aand move toward the house, the impact will be directed away from the house. When you get closer to the house, aim the jackhammer away from the house. By the time you get close to the house, the consrete strip should be thin enough to break easily and not require much impact. I probably would not use a skidsteer or backhoe mounted jackhammer (Ha Ha), especially if you have an old and crumbly foundation. As for the support. I would cut it out at least 16"x16". If it is not thick enough, it will crack under the weight. Then you will have to support the patio and put a more substantial footing under the support.

I bear no responsibility nor assume any liability for any misfortune or damage that might ensue from my advice.

If too much in doubt, get a pro.

Thank you all for the feedback and comments. The number and quality of responses was beyond my expectations.

CaptMoosie and some others requested additional information regarding the project (i.e., pictures and measurements). I tried to address all of your questions below. I apologize for the length of the post, I tried to be succinct.

Just a quick personal note. Yes, I am a DIYer. Not necessarily by choice but by financial restriction. As I read and reread your comments, if I feel I cannot safely peform this project then I will be sure to hire a professional. So please know that I will not recklessly begin this project and I do sincerely appreciate your disclaimers, warnings, and notes. I want to live--I promise! I'll also follow all codes and get permits if needed. Calling the city about this is also on my to-do list.

Here is the concrete patio to be destroyed with the deck above. The patio's dimensions are 16 x 12 (about 190 sq. ft.) and is about 4 inches thick. The deck is about 9 1/2 feet above the patio.

You will see that the patio is adjacent to the house on two sides and will see the single support column. Below is a closer look at the column.

Regarding the dimensions of the colum. There are three posts that make up the iron (?) column. Each is a square with a width of 1 1/4inches. Here is a closer look at the top where it supports the deck. The column is attached with two bolts. View is from inside the patio.

Here is the view from outside the patio of the same thing.

And below is where the column support attaches to the concrete patio. There is a small footing on the patio that the column rests on and is attached to.

So, regarding deck support while I am removing the patio, I'm thinking of cutting out two, two foot squares on the edges of the patio about a foot on both sides of the base of the column. I will then provide a sturdy base to attach shoring posts to support the deck while I remove the column. I assume shoring posts do the same job as lally posts. Regarding a replacement post, I'm a bit at a loss for what is needed that would bear the load of the deck. Any suggestions would be greatly appreciated (I assume I would use a 4 x 6 or a 6 x 6 treated wood post). I plan on attaching the correctly sized post to a pier with bracket, on top of a large concrete square, on top of a foot of compacted gravel. The frost line where I live is 10 inches, so this should protect against frost heave. I live in Portland, OR where it gets wet but not too cold. I did a web soil survey on the USDA site and didn't quite understand the results, so I will do more research on that. I'm not sure how to determine groundwater under the patio. How do you find that out?

Regarding the construction of the deck and how it is attached to the house, as you can see from the pictures, the bottom of the deck is covered so I cannot view the ledger board or the joist hangers. If that information is needed to determine load on the column, I guess I'll need to rip off the plywood and provide some additional data.

Regarding concrete removal while not doing damage to the foundation of the house, it appears the patio was poured separately from the foundation. Please see from this picture.

So, I like the idea of using a saw to cut the concrete and then using a sledgehammer when getting 2 feet or closer to the siding.

Thanks again for all of your feedback. If you feel like I totally missed something, please let me I'm an idiot, quit the project planning, and write a check. Thanks so much.

Robbie

The first thing you need to do is to brace up the floor of the upstairs patio with at least a 6 by 6. Then you can safely remove the metal support at the corner. You can then safely remove the area that is currently under that support and pour a new footing for the support column. I would suggest burying a couple of J bolts in the footing so you can bolt down the metal support. Put the column back to support the second floor. You should get or rent a small impact hammer and use a star drill to drill holes through the concrete about four inches apart next to the foundation. That procedure will prevent breaking parts of the foundation when you get close. Using a concrete saw to get the patio cut into pieces is a good idea. You can rent one. They take a lot of time and use quite a bit of water. You should make a trench around your patio and dig a shallow ditch toward the lowest point on your property to flow the water away from your work. If you choose to use a jack hammer make sure that you have a way to mist the area that you work to keep from breathing the concrete dust and make your wife happy that everything in her world is not coated in dust.

The most important part of this suggestion is the use of a star drill so that you don't end up breaking your foundation. Good luck with your project.

Robbie,

I used to run a jackhammer for a living and what I would do when I needed to make a close cut or when I wanted to leave a section I would take the pointed tip and just punch some holes in a line and then take a spade tip ( used for black top ) and cut between the holes. This was always faster and gave me a cut just where I wanted it. I got close to foundations without hurting them. If you need a even line around the post then you will need a saw but I always poured fresh concrete when I had a case like that.

Lots of great advice here. I have one last thing to add that is safety related.

I recently read an article about a worker that while cutting through a concrete slab also cut through an electrical conduit and the live wires within. The story didn't end well.

It is time well spent to make sure you know where any underground utilities are. Use your local "One Call", a free underground utility locate (in the states I've lived its use is required by law). They won't do your service lines, but they will point out any lines that may run through your property.

Very good sound advice CI!!!!

Hello Robbie,

Thank you for providing the photographs and measurements.

First thing I'm going to tell you is that you're going to need to hire a Licensed Structural Engineer Registered in the State of Oregon. There are several reasons why I am providing this advice.

I took a look at the State of Oregon Snow load Manual which the City of Portland uses. There is a Minimum Design Snow Load of 20 pounds per square foot (psf) + 5 psf rain load (atop the snow) as a recommendation. However, the Design Snow load can vary considerably even in Portland OR depending on where you actually are located, with special emphasis placed on your Elevation above mean sea level......higher elevations will experience higher snow densities and loads.

Also, it appears to be that you have a standard hip roof where one half of your roof parallels the long axis of your 2nd floor balcony, and that it sheds towards that balcony. In my professional opinion there is a strong chance, depending on the severity of your roof slope, that snow will slide down your roof and cause what is called a "snow drift" occurrence on top of your balcony. This additional snow load must be taken into account when designing a replacement corner column together with a new concrete foundation. I do not believe that the minimum City of Portland snow & rain load will be applicable in your case. It'll be much more heavier and compounds the problem. The PE that you hire can determine the snow load pursuant to the State of Oregon snow load maps together with the use of the following American Society of Civil Engineers (ASCE) Manual:

"Minimum Design Loads for Buildings and Other Structures"

It's a very involved procedure to determine the snow drift loads, and a PE in your locale would be much more in tune with the actual conditions there than I could ever be (I'm in upstate NY).

Also, there is a chance that even a 6x6 wooden column may not be able to support the design snow load on your balcony due to it's height of 9 feet (slenderness ratio of the column will dictate the Maximum Allowable Compressive Stress as well as the Maximum Allowable Axial Load) of the new replacement column. Here again, the PE can determine the most suitable column (material and size).

The PE can also design a reasonably easy-to-build concrete column pier to install under the new column. Personally, I wouldn't use anything less that an 8-inch diameter concrete pier (use a Sonotube to form it....this can be bought at Home Depot or Lowe's) at least 30-inches deep (below the ground line), 3,000 psi minimum concrete compressive strength (f'c) and a minimum of 4 x #4 rebars (ASTM A615, Grade 60) vertically oriented and #4 Tie bars wrapped around the vertical bars every 8-inches.

No doubt in my mind that you will most likely need a concrete pier footing to spread the load into the soil mass within reasonable limits. A lot depends on the composition of the soil at the corner column location. Again, the PE can determine at least a "Presumptive Allowable Soil Bearing Pressure" so as to determine the minimum footing size using the Applied Design Load from the new column. For a project of this scale I don't think there's a need for soil borings to determine the soil bearing pressure. As far as ground water issues are concerned, high levels can impact the soil bearing pressure. Has your basement (if you have one) ever experienced groundwater infiltration problems in the past? You can always dig a hole or auger one down 3 feet to determine if you have groundwater issues.....make sure the PE sees the hole before you fill it in.....there's such a thing as "seasonal high groundwater levels" that have to be taken into account....the engineer can usually determine this by observing the soil compositions and conditions.

If you have any more questions, please feel free to ask away.

Robbie,
You've gotten excellent advice from the guys here, and it seems to me that you are a reasonable fellow. One last thing from me.

That looks like a lot of work, assuming you aren't going to leave a hole where the patio is. You'll have to break all that concrete into pretty small pieces to make it manageable.

Wear and tear on you, wear and tear on the neighbors ears as you cuss the project that should have been done yesterday, wear and tear on your pickup or hauling vehicle...............................Aching back.......................

Write the check, Robbie. Call the man, Stan. Sit back and relax, Jack.

Then, as you are sipping a toddy and watching the 20 year old kids sweating their tails off, you can take pictures of the progress and post them here.

However you do it, be safe; Have fun.