How to form slab with attached porch?

[krazykevin76]

How to form slab with attached porch? One pour or two?

Quick question for the concrete gurus. I'm going to form up my slab and do everything I can to save some cash so I can spend a little more on my shop. I'm going to have a 40x50 shop and I'm going to have a 12ft porch that runs along one of the 50' sides.

I'm going to form the shop up for a 4" slab with a 1 1/2" x 1 1/2" groove around the edge for the tin. Now, for my 50' side that I"ll have the porch on: I would think I would make the porch offset from the slab by 1 1/2". That way the tin would be uniform all the way around and water can't run inside my shop from the porch. I was also thinking about sloping the porch a tad for run off. "IF" all this sounds fairly right to you guys, how do you go about forming this up? Can you do this in one pour? Or am I going to have to form the shop, then knock the form board down and then pour the porch serperate? I'll just be doing the forming and will hire out the finish work.

What is the proper way to do this? Is there a good site that covers this? I've searched for a while but don't know exactly what to search for.

Thanks in advance.

Kevin

 

[jkwilson]

I'm not a pro by the wildest stretch of the imagination, but I have been a part of enough stupid concrete mistakes that I might be able to offer some advice.

I'd think it should be two pours without a doubt. The finish on the surface will be different for outdoor concrete, and it always makes sense to break up a pour when you can. You don't want them attached because they will experience different temps and moisture.

I'm concerned about a 1.5" groove in 4" concrete, metal in direct contact with concrete and metal below the grade of the floor. Heck, I'm concerned about 4" concrete to start with.

What kind of construction are you doing, what do you plan to use the shop for and what is your climate like?

 

[srmofo]

All of his concerns popped in my head also.

They don't pour driveways with the rest of the house. You have enough for another pour,why not do it

 

[krazykevin76]

Re: How to form slab with attached porch? One pour or two?

The slab will have 12x18" beams around the outside and one through the middle. Setting rebar on 12" centers throughout. We are in East Texas, frost not really an issue. This will not be industrial use. Mainly lawnmowers, four wheelers and automobiles. I am by no means a slab expert but dozens of slabs in my family and neighbors are 4" and have no issues.

I do agree with the double pour though. Seems like that is what makes the most sense.

 

[joes169]

I pour concrete for a living, and although we technically "could" pour the stoop at the same time, I'd have to dig hard for a good reason to. It's just simply too much work to make it turn out correctly. Be cautious of any contractor who tells you otherwise, as they're likely more concerned with making a bigger profit by not coming back vs. doing it the logical way........

 

[ConCretin]

I'm with Joes169. You could hang some forms and place it all together but it would be more work than it's worth and you'd probably have problems with grade and/or finish. Place it in two sections.

4" slabs are fine - it's what's under the slab that's important.

 

[southernfriedcj]

I've poured 100's of porches with the slab(driveways too).

The only issue I have ever seen is when you cut a joint in the slab and don't carry the joint on through the porch. You will get a crack across the porch off the end of the slab joint.

We trowel a joint in the porch to line up with the joint that will be cut into the slab.

The way we run our forms is, we use a 2x8 for the slab and a 2x4 for the porch. The section of the slab that meets the porch gets a 2x4 and the concrete runs under the 2x4 slab form(the bottom of the 2x4 slab form at the porch is the top of the porch pour).
The forms on the side of the porch have fall away from the house.

Here is a pour that included 2 house slabs, 2 patios, 2 driveways and 1 garage. One pour. We rarely use a pump, but those are tiny lots and there is no way to get a truck on them(both house are in the pictures below, it's tight in there).

You can see the forming system I'm referring to in the first picture.
The guy in the green shirt is standing in front of the garage, there is a sidewalk to his back right, it steps up to the patio which steps up to the house.

​

These pics are just pour ****:

​

 

[krazykevin76]

Still a little confused. Guy in green, he is facing the garage correct? I can see the 2x4 on its side creating the height difference. How do you handle your stakes being inside your pour area? If I lay 2x4 50ft the width of my porch and shop, that is a lot of stakes in my porch area. Do you guys just pull them out and patch over and smooth? Am I missing something?

 

[southernfriedcj]

Still a little confused. Guy in green, he is facing the garage correct? I can see the 2x4 on its side creating the height difference. How do you handle your stakes being inside your pour area? If I lay 2x4 50ft the width of my porch and shop, that is a lot of stakes in my porch area. Do you guys just pull them out and patch over and smooth? Am I missing something?

He is facing the garage. That garage will have a 7" "stem wall" so to speak.

The stakes that are inside the pour are pulled up as they are finishing the concrete. They put some concrete in the holes. You cannot tell where the stakes were after the concrete is finished.

The underside of the form board that is running away from him is the top of the slab.
You can see that it is ripped down at an angle(gets "skinnier" towards the back of the garage) to give the garage slab some fall.

The 2x4 form that is flat, directly in front of him, drops the very front of the garage slab down 1-1/2" to create a lip that is level with the driveway and that stop water from blowing under the garage door. The bottom of the garage door rests in the area.