How to screed cement pad with walls on three sides?

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Old 07-31-19, 11:25 AM
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How to screed cement pad with walls on three sides?

So I'm laying this pad in front of my house, and trying to decide if I can do the cement myself or if I'm going to have to hire someone to pour it. I can get it prepped and gravel and grating down and everything, but with house foundation on three sides, I really don't know how I'd screed it. Anyone know how I would accomplish this?
Sorry here is a pic
 
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Old 07-31-19, 11:52 AM
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My concrete person marks the line they want on the walls. Then they just hold the screed board at that height.

For large areas in the center of a pour they drive rebar stakes to the height they want the concrete. Then they screed to the top of the stake. Once the screeding is done they hammer down the stake and do the finishing.
 
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Old 07-31-19, 11:56 AM
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Thanks. I guess I hadn't thought about the fact that I don't need to rest the screed on forms and can just eyeball it on my line. Should I put expansion joints against my foundation? I don't imagine I should cement right up to the foundation in my zone, where we get cold snowy winters.
 
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Old 07-31-19, 02:31 PM
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Another question, do I need to form around that cleanout pipe, or can I just cement around it? Same with the black rain pipe on the right?
 
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Old 07-31-19, 02:40 PM
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On a job I contracted out for, they used 3M spray on adhesive around the perimeter (it was blocked in on 2 sides). They then unrolled some (1/4") foam strip on. The height was set at where they wanted to screed.

After the concrete set, they tore off the top (1/2"). The foam came with a tear off strip on top. They then caulked with some type of outdoor concrete compatible product. It's been about 5 years and still looks good.
 
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Old 07-31-19, 02:41 PM
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If it was me, I would get foam sill sealer or expansion joint and wrap those pipes with that. That will create a gasket and a spot to caulk later. I wouldn't want concrete tight around them since any shifting would tend to crack the pvc.

Most guys I have seen will snap chalk lines and put expansion joint against existing concrete and against the house. Then as they pour the perimeter they will trowel the perimeter roughly with a wooden float while they are standing in the concrete. Pour about 3 feet more and then screed it off by following the surface they just trowelled... and repeat until they are finished. Then a bull float evens it all out and a Frisco finishes it.
 
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Old 07-31-19, 03:00 PM
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Great information, thanks! I like the adhesive and foam strips around the perimeter, as well as wrapping the pipes. One other question, with this size of pad, should I cut in some breaks in the concrete? If so, where? One down the middle perpendicular to the sidewalk?
 
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Old 07-31-19, 03:12 PM
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Concrete wants to crack on its own (uncontrolably) anytime one side of the rectangle is >1.5x the length of the smallest side. So if your pad is, say 8x13, you would want to cut it in half, into 2 pc 8 x 6.5. But if it is 8x10 it does not need a joint.

If concrete does develop cracks on its own even though the size and shape was within that tolerance, it is often due to improper compaction, or improper drainage, or expansive soil, or some combination of the above. Cracks will also develop from cold joints... such as from a long pause during pouring, or from different batches (both of which should be avoided). Odd shapes will also crack, so for example you would not usually want to create a narrow pie shaped piece because they will sometimes break in half.

Finally, if your pad rests on any of the sidewalk concrete (sometimes there is slag underneath that acts like a footing), the expansion joints in the sidewalk will tend to want to telegraph through to the new concrete behind due to the slight movement that is potentially there. You see that a lot when a sidewalk is poured over top of a curb, for instance. The sidewalk will always crack wherever the joint in the curb lies.
 
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Old 07-31-19, 03:42 PM
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Thanks sleeper that is great info.
 
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Old 07-31-19, 04:19 PM
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I know it's extra work, but you might think about digging down where the gutter drains and installing some smooth wall into a 90 (or better yet a long sweep). At my house I have some of that black corrugated pipe that dives under a sidewalk like yours and occasionally I have to clean it out and it is a pain because it's difficult to make a turn with the hose.

If the black pipe makes a sharp turn it's more likely to get plugged.
 
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Old 08-01-19, 01:25 PM
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Ha well I wish I had the energy to pull out that drain pipe and replace it. But I've already run that white pvc pipe under the sidewalk as an empty conduit for the future if I have to re-run the sprinkler control lines down the road, which took me a good amount of time. Trying to dig out that corrugate drain line would be more than I can handle right now. I've already spent days getting it to this point. I honestly don't even know that I could physically get that line all the way out. It doesn't just go straight down, it does curve and go under the cement. Not sure how far it goes out, or if it drains to the storm drain or what, but I think I'm going to just have to deal with cleaning it out in the future if it ever gets clogged. Worse comes to worse, I disconnect it from that drain and let it drain onto a ramp right on the patio and it will just drain onto the lawn.
 
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