Pole building foundation question

[rademamj1]

Im guessing they are compacting it just a few inches at a time?

You are very close on your statement. The tracked skid steers i saw building foundation pads, would spread a truck load of select fill, then compact that load,, while the next truck load is moving into dump position. And repeatedly....until the pad reached its planned 28" thickness. It was for a 40'x75' pole barn, requiring 145 cubic yards fill, and was completed in just over 10hrs work.

So you really don't spread all the 145 cubic yards of fill first, and then compact with the tracked skid steer. Its done incrementally, by compaction of each truck load as it is delivered.

 

[mikester]

Footings should be on undisturbed subsoil. If you place footings on fill hire an engineer to look at your soils and make a recommendation on fill placement and compaction procedures.

If you don't have a clue hire the engineer to supervise the fill and compaction process.

I've seen far too many half a$$ed compaction jobs and heaving foundations and floor slabs to take the recommendation of some contractor who just wants in and out in the quickest amount of time in order to cash your hard earned cheques before you can put a stop cheque order in place.

 

[Egon]

Proper compaction and looking good are two different things.

 

[etpm]

Footings should be on undisturbed subsoil. If you place footings on fill hire an engineer to look at your soils and make a recommendation on fill placement and compaction procedures.

If you don't have a clue hire the engineer to supervise the fill and compaction process.

I've seen far too many half a$$ed compaction jobs and heaving foundations and floor slabs to take the recommendation of some contractor who just wants in and out in the quickest amount of time in order to cash your hard earned cheques before you can put a stop cheque order in place.

About 20 years ago I had built for me a building destined to be a machine shop. One of the things the machines could not tolerate was an unstable foundation. I spoke to the county building department about this. They required ANY slab poured on grade to be on undisturbed soil after a certain amount was removed from the top. Loose soil, leaves, branches, duff, etc. But after that requirement any leveling before the pour could be done would only be done by removing soil or having engineered compaction.
As it turned out it looks like the county has good requirements. My slab has survived the heavy machines on it during an earthquake. One machine, while it weighs only 8000 pounds, sits on only 4 feet, each foot seeing only 125 PSI. But the footprint of the machine is only 2 by 4 feet.
I am very happy the county rules are what they are. These rules are part of the reason that machine can hold plus or minus one ten thousandth of an inch tolerance all day, every day. An unstable foundation would not allow this.
Yeah, my example might be extreme, but a pole building can't have rocks subject to freeze thaw motion supporting it. Freezing water moves huge rocks large distances over time. Having a concrete footing below the freeze line, on undisturbed soil, makes all kinds of sense.
Eric

 

[Larry Caldwell]

The foundation of a pole barn is at the bottom of the hole. With a 4' frost line, dig a 4.5' hole, dump 6" of concrete in the bottom, and there's your foundation. Concrete walls between poles are retaining walls, and need to have a retaining wall footer. The footer in this case would extend inside the building so fill would sit on it to hold it down. For a 4' retaining wall holding compacted fill, the footer would be about 3' wide, with rebar hooks that extend up the wall. It doesn't need to be connected to the building at all, though people often drill through a post and run rebar at the top to keep things sort of lined up.

 

[Farmer495]

Footings/ poles go into the undisturbed soil. When I built I was on a 2 foot difference, my down hill poles are really two feet longer than the uphill ones. Onces the poles were all set, then I put and compacted fill.

 

[LouNY]

That's your thinking. But you have never actually tried using a tracked skid steer for foundation pad construction, or you would not be saying that.

He is also a long way north of central Texas.

The contractor desiring to put in stepped footers and a sile wall is doing the proper base how well he compacts the fill inside will determine how well the concrete floor works or if it cracks and tilts.
Also a post and beam structure would amount to a pole barn on poured walls

 

[forgeblast]

I'm planning to construct a 48 wide x 40 deep pole building on a site that has a moderate slope. So, the floor level at the front of the building would be just above grade at that location, and floor level at the back of the building (40 feet back) would end up being be about 4 feet above the grade at that location. In other words, the grade slopes down as you go from front to rear.

I do want to have a foundation wall, as opposed to putting poles in the ground. Location is Wisconsin, so planning for a 4 foot frost depth is required.

I'm getting quotes from various contractors. One contractor proposes to pour taller foundation walls at the rear, about 8 feet total wall height (4 feet of wall below grade and 4 feet above). Sidewalls would "stairstep" to only being 6-ish feet tall (2-ish feet above grade), and front foundation wall would be 4 feet tall (mostly/all below grade).

Another contractor proposes to use a uniform 4 foot tall foundation wall all around, but also install crushed rock on the rear and sides, underneath the concrete foundation wall, to a depth of 4 feet below grade.

I'm sure the first method is "better" (and of course more expensive). But I'm wondering if the second crushed rock under concrete method is "adequate"? It would obviously save a lot of the concrete cost, but I want my building to be stable and long-lasting.

not sure if other people mentioned it but its sounds like the last foundation they are recommending is a rubble foundation. I have used them before and have had no issues in pa. My first I dug down below frost level, and sloped one side to daylight. Put in some 2b and packed it. then put in 4' perforated pipe, and more 2b, until i was 1 1/2 feet from the top, put in tarpaper, and added rebar. poured my foundation pad right on top. Then built 1' thick stone walls for my 10x10 shed, it has a second floor in it), no movement etc. The larger building we are working on now will be a 16x20 sap house. Same way rubble and fieldstone walls. These walls will be about 4' high then wood ontop depending on how much stone we have left. Frank lloyd wright used it in a bunch of his houses.

 

[Larry Caldwell]

Frost heave is from freezing water. If your rubble foundation sheds water, it probably will never heave.

 

[Egon]

Frost heave is about capillary action that some soil types will support.