[detroiit]

Hello Everyone,

Was wondering when pouring the foundation walls/porch for a new construction residential how come with the smaller porch design (plan1 and plan1.1 jpg) does the foundation wall extend all the way down to basement and is closed off and then just filled with dirt for the slab to rest on.. is it more efficient this way or is it because it is a 2 story entrance? The other plan2 and plan2.2 has a bigger porch but is UNexcavated and looks calls for cmu or poured stem wall but is not a two story or is that because it is inefficient (waste of concrete/expense) this route so they would backfill as normal up to the main foundation wall then trench out?

Thank You

 

[detroiit]

Is one at ground level and the other in need of stairs off the porch?

They both require a step onto porch.

 

[detroiit]

I don't understand what he wants it for.

The question is about the foundation wall extending down to the basement and closed off vs the plan with the larger porch is unexcavated. Was wondering why the excavate all the way down and finish off the porch well below for the smaller porch.

 

[detroiit]

The reason is the excavation overdig.

• The shallow porch is within the basement's overdig, and you can't levitate the porch foundation pour in the air, so it will be a full basement story pour. It doesn't matter structurally, it is only about methods of construction. Waiting for backfill then pouring the porch later would just settle with the backfill and extend the foundation pour project timeline.
• The deeper porch is beyond the basement's overdig (that example drawing may not have a basement anyway, and the porch is shown as a trench, but for discussion it has a basement and porch footings). So the porch foundation can just go to frost depth, and the part of the porch foundation wall will be bridged into the basement wall (haven't seen it done, but it appears the "CMU Lead" is filling under the bridge with CMU).

Here is the excavation in RED for the full story basement, in BLUE just to the frost depth:
View attachment 722156

OVERDIG! That makes sense. So the main reason is efficiency and as well as the over dig area if it remains mostly undisturbed in the bigger/deeper porch allowing the soil to not have to settle then it's good and they go 42" below after the basement is backfilled for porch footings. But like @Matt1963 is saying that is assuming they do not even have to dig even further which then in turn that entire porch area would be done with the basement like the smaller porch and filled with dirt and then do the slab as usual I'm assuming since it's possible it could be in the overdig area.

Both plans do have basements and to the right are the garages.

 

[detroiit]

Because you have a 42inch min cut (Frost) then you most likely will be ok in picture two. (It's 12 inches were I am)

To be in a safe working hole, labor and industries in my state makes me be 2 ft clear at the bottom of a hole, then I can go straight up 4ft and then 1 to 1 slope from there to the upper grade.

So on an 8ft cut (basement) you would then bench cut about 4 feet up and excavate the porch from there. Footing and walls would tie in and just step to grade. One pour.

Other factors can apply.

Are you trying to figure out budgets based upon designs?

When estimating these kinds of excavations and foundations one must do an educated guess and then explain to the owner how such estimates were done.

Most builders are much more comfortable after the hole is backfilled.

Makes sense so the the bench cut area is pretty much left alone and the 2ft clear area would just be back filled and as you stated there is a 42" cut after the fact so porch can be trenched out after and either poured or cmu block. The reason behind this was to see how excavation efficiency plays a role and this can be done with budget based on design, yes.

 

[detroiit]

No, and I think you are even misunderstanding what Matt1963 said. You do not backfill and then re-excavate later for the porch when you have frost footings. Everything is dug at once, porch and all. A "bench" cut, if used in excavation, has to do with the earthen walls caving in, not the foundation. If the upper tier (the "bench") happens to be at the depth of the porch frost line, so be it. Whether you do a bench cut, or the angle of repose has to do with the type of soil you are digging in.

Okay I see what you are saying now so it's all done at once. The area up against the foundation wall say if the wall is 8' and there is a 2' setback that is completely dug out all 8' down (the area you have showing in red) but 6' back where the bench cut/porch is (area shown in blue) you take down only 42" and pour the footings just for the porch so not as deep as the foundation wall and build up the porch all in one go. The area between would be re-filled though I'm assuming (shown in purple). P.S those racoons are too damn cute lol.