Dug to deep

[Blueboy7]

Adding on and dug one area for the footer to deep 18" in the lowest spot gradually going up to where it should be over a distance of 20'.

My question is what material would be best for compacting. The ground under the garage is shale. I was planing to use 2A limestone (some call it modified limestone).

Thanks!

 

[LXCam]

Fill it with concrete and be done with it. It's not worth the effort or taking a chance on getting compaction.

 

[pcmeiners]

Perhaps a finer grade but 2A will do. At least you are correcting the issue properly, around here (NYC) I have watch a few GCs over dig , not corrected at all, and have footings/foundations crack in a few months.

 

[pamike]

Fill with concrete...

 

[matt_i]

If you have a footing inspection, the inspector will likely make you dig out the gravel you put in there back to clean soil, thus making it even deeper. As above, fill with Concrete.

 

[Blueboy7]

I should have mentioned the total area is 18"D x 20' L x 16' W. So I have to build up the area anyway because of the floor. And it's going to be 8" block 20 rows high.

pcmeiners, what do you mean finer grade, 1B or something? Would it hold up better?

No inspections.

 

[jackson1701]

Either dig to level it out and fill with concrete or dig to level out the deeper end and make a step in the foundation and use block to bring it to grade. adding fill will weaken the footer and cause it to crack over time.

 

[vekster]

fill with concrete is the only way in my opinion

if it was a floor fill would work.....3/4" clear
but a footing no way just use concrete

 

[Rookie2]

gravel will hold water . any fill needs to be compacted till you run out of fuel twice ! I would as others said pour a taller footer in concrete or build up with block. You can fill in with modified later and compact.

 

[Stuart in MN]

The idea is the footing is supposed to be on undisturbed earth. It will be simpler in the long run to just pour the additional concrete, instead of trying to fill and tamp the trench. There's no harm in having a bigger/deeper footer than the minimum requirement.

 

[Richard Cranium]

As the group has said, fill it up with concrete, You will never have to look back at it and be sorry.

 

[mikegt4]

As everyone says, an inspector will insist on undisturbed dirt. If no inspection and you build over gravel we will expect a "why is my garage foundation sinking" thread in the future.

 

[the GOAT]

Stepped footer.

 

[rburke65]

Concrete andbedone....move on.

 

[brownbagg]

If you have a footing inspection, the inspector will likely make you dig out the gravel you put in there back to clean soil, thus making it even deeper. As above, fill with Concrete.

not me, we use a lot of gravel in footing backfill, nothing wrong with it

 

[kaymccampbell]

I like damp crusher run compacted in 2" lifts. Our inspectors pass that like it was concrete.

 

[Blueboy7]

gravel will hold water
undisturbed earth
fill it up with concrete

Points made and understood. It's going to be some crazy looking forms but the concrete will be on solid ground.

Thanks for the advice, it is much appreciated!

I'll post some pics...

 

[johninct]

Fill it with concrete and be done with it. It's not worth the effort or taking a chance on getting compaction.

Do this!!!!

 

[brownbagg]

gravel hold water, yes, that the purpose of the gravel and then the water will perk into the soil. but gravel will hold the loads better than undisturbed soil, which is classified as uncompacted soil.

 

[flan]

3/4 washed gravel compacted works nice

 

[Blueboy7]

3/4 washed gravel compacted works nice

Just curious, why washed, wouldn't you want the finer parts to hold it together?

 

[Marctrees]

I figure you need roughly one extra yd of concrete.

Do the math.

No big deal.

Marc

 

[Blueboy7]

WWBVD? (what would Bob Vila do) LOL

 

[csp]

There are places where the existing soil ***** and local building jurisdictions require builders to remove and replace with compacted soils that are stable for building on.

Some compacted materials are better than undisturbed soils.

 

[flan]

Just curious, why washed, wouldn't you want the finer parts to hold it together?

3/4 is essentially self compacting stone. Add fines to the mix you may get it compact, if it has a way to wash out (high water table, etc.) those 3/4 are left behind and the fines travel elsewhere, maybe cause a gap. I had to dig past my footing depth for stump/root removal and that's what I researched and decided to use. 3/4 with fines is a great base material for roadbeds, deep fill under slabs (I used 180 tons worth), etc. packs like concrete. Google "self compacting stone" for lots of opinions on using 3/4 or similar.

 

[pstnbly]

Stepped footer.

^^^^^ This

 

[Radix2]

Stepped footer.

If it really is only a yard difference in concrete - then the cost and time to step the footer and lay additional blocks is going to be more than just pouring the extra cement.

K.I.S.S.

 

[Firebrick43]

gravel will hold water
undisturbed earth
fill it up with concrete

Wow! Talk about mis information. First you don't used gravel (or pea stone) you use crushed stone of medium size such as #8's or #4's without fines. But even if it was screened gravel it doesn't hold water. Don't believe me. Take a bucket and cut out a 3" hole in the bottom. Put a square of hardware cloth in the bottom and fill with crushed stone. Pour a gallon in the top and see just how much and how fast the water comes out. Now fill the bucket with soil and see how slow and little comes out, even sandy soils that drain well are not as good as crush stone.

As everyone says, an inspector will insist on undisturbed dirt. If no inspection and you build over gravel we will expect a "why is my garage foundation sinking" thread in the future.

They insist on undisturbed soil yes, but perfectly ok with properly compacted stone on top. In fact it's a plus. Roman roads but over two millinium ago were built on layers of crushed stone and many are still in use today due to there good drainage and stabability. All good modern roads are on a base of crushed stone as are railroads. Many of the precast basement foundation systems are placed directly on a trench filled and compacted of crushed stone to serve as a footer. I could give example after example but a Google search will educate one as well

 

[Blueboy7]

I got the rest of the digging done and after surveying the whole area I figured it would be easier to add another corse of block, so that will make it 21 rows. The deep area will be 10" instead of 18". The extra corse will give me more room for a lift.