Fill and gravel

[mshedb]

Learned today that I have up to 3' of fill in the area where I plan to build a 26x32' garage. Geotech has recommended footings at 36" or through all fill, and removal of fill and replacement with gravel. That's 81+ cubic yards of stone - must be over 450 tons of rock to do that. Have others encountered this problem (is it a problem?) and how did you address? Thanks.

 

[Poltax]

What type of fill is it? If its concrete bits and misc, rocks gravel and dirt, then it will be a bit hard to compact. If it is just misc dirt then rent a compactor and hit it over and over. The problem with rocks and concrete in fill is that even if its compacted you will still get shifting and sinking. Then your floor, & footings, will crack & sink or shift. You will need footings any way with a garage that size.

 

[brownbagg]

we use sand as fill

 

[rodnok1]

I couldn't see any reason for using gravel 3' foot thick. Any compactable clean fill should be acceptable. Sand is generlly cheapest. I would dig some of your fill up and see what it is like was mentioned by Poltax.

 

[Sundowner]

With bridge design, we use gravel more often than not for 'small' fills like that. it's free-draining, doesn't swell like organic soils, has superior active pressure properties to every soil out there, and (around here) it's usually cheaper than buying clean fill.

 

[arbee]

My interpretation of the original post was that the fill is already in place where he wants to build. Is this correct?



The spot my garage is on had about 5 feet of slope from front to back to deal with. I talked to a Geotech Eng firm about what my options were. I had a big cut area out in front I could pull fill from that I wanted to take advantage of. I also wanted a leanto on one side. My choices were:

1. dig footings and build a traditional foundation wall and back fill with sand, stone, or carefully compacted fill.
2. Fill the area in 6" lifts, rent a sheeps foot compactor, have Geotech firm on site during entire fill process to measure compaction
3. Filll the area in 6" lifts with a dozer with no Geotech firm on site. Then dig through the fill to orginal undisturbed soil. Back fill this up to 5' deep trench with clean washed stone of all the same size (which will not compact) and pour footings on this near the surface of the fill.

I looked the costs of the options and what the lay of the land would be like when done and went with 3. This is also known as a rubble trench foundation. My website below has pics of the finished product but I haven't added pictures of the process yet.

I'm not sure why the Geotech would insist that the fill be removed if you've dug through it for the footings which will support the building.

 

[ownsaglock]

With bridge design, we use gravel more often than not for 'small' fills like that. it's free-draining, doesn't swell like organic soils, has superior active pressure properties to every soil out there, and (around here) it's usually cheaper than buying clean fill.

Same here. Cheaper to haul in stone than suitable dirt for us.

 

[kbs2244]

If your fill is over 3 years old it has settled down just fine. As long as you are not planning on parking something super heavy in the garage, I would just go with a normal slab with a good rebar job.

 

[Herb]

Gee, why fill and worry about settling when you could just dig a little deeper and have a basement under you garage? That is what I did.