Building site prep and soil compaction

[skipperbrown]

I'm getting ready to start a 5000 sf Morton building on a 5800 sf pad. The 800 additional is porch. Morton wants to erect the building on dirt/gravel and then have the slab poured after they are gone. I watched a video of a family putting up a Morton, and they rented a vibratory sheepsfoot to compact the soil during site work. It did such a good job they had trouble digging out dirt for water and power lines before the slab pour. It's about time to start site prep and it looks like we will need to bring in about 10 to 20 loads of dirt after scraping off the topsoil. I asked my dirt guy what he was going to use for compaction and he said he just used his dozer. I told him I wanted a vibratory sheepsfoot and he said that would be fine, he would rent one. He called me yesterday and said the only one he could find was $850/day and he'd need it 3 days. That's approaching 1/2 cost of the entire site work expense. He said he had a buddy with a roller and he would check the cost of getting him in.

I read somewhere that you should compact after every 6" of fill was added. The building is in east TN and the dirt has a high clay content.

My question is this: How much compaction do I need? How much weight do I need to get it? What kind of equipment should I be looking for to fulfill the requirements? Will a roller work? What about a pull behind sheepsfoot? Morton isn't a lot of help since they don't warrant the slab. They just agreed that having the site compacted was a good idea. I want to do this right but I'm at a loss as to what equipment will get the job done and how I know the site will be ready for a pour. Your thoughts are appreciated.

 

[747driver]

How deep will the fill dirt need to be to get you to top of grade after taking top soil off ? Remember to include the thickness of the stone you put down. I live not far from you in Tenn. I have the same type soil. In parts i had 2' of fill to build up. I just filled in 4" lifts and compacted with my tractor by going back and forth. I kept the soil damp as i compacted. It was easy to get if very firm, then i added my stone and used a plate compactor to vibrate the stone. I have been told that bulldozers are not a ideal choice for compaction...those tracks are meant to just kind of float on top the soil. Morton done our barn 18 months ago.

 

[EddieWalker]

Back in the late 80's I worked on quite a few jobs in CA where compacting soil for commercial buildings and roads had to be over 99%. The inspector tested compaction with a box that I believe was radioactive, and it sent a signal down into the ground and back up again like radar. This showed him how compact the soil was. If we didn't hit 99%, it was dug out, remixed with water or dry soil, and then put back in layers with a vibratory roller going over it. The hardest part in getting proper compaction is having the correct amount of moisture mixed into the soil.

If you don't have the correct amount of moisture, you will never get compaction.

Having said that, and being honest about what I do for my own projects, you don't have to have a vibratory roller. You do have to have something better then a dozer, which is the very worse machine for compacting soil. I have a full sized backhoe with a one yard bucket. For my projects, I spread the dirt several inches with the back of the bucket, then with my next load of dirt still in the bucket for maximum weight, I drive over ever inch of that spread soil. Then I dump that load, spread it out and go get another bucket of dirt and drive all over that spread soil again. I do this for every load of dirt.

In my experience as a contractor, I've learned that when somebody does not want to do something, they create fake barriers to try and convince the client not to do it. Most common is lying about Code. Second most common is lying about what it will cost or how long it will take to do. In your case, I looked up what it costs to rent a vibratory roller from Sunbelt. It's $365 a day for a 48 inch roller and $595 for a 52 inch roller. Compaction Equipment & Tool Rentals | Sunbelt Rentals

There is no reason that you cannot do 6,000 square feet in a day. It should be an easy day at that!!!

 

[skipperbrown]

Thanks for the comments. I think the deepest amount of fill will be about 24" on one end of the 50' wide building. My sister called a retired commercial builder and he suggested hiring a dump truck operator with a full load to run over it as dirt was spread on the site. This would approximate what Eddie is doing with his loaded backhoe bucket. I have a local retired guy with a single axle dump truck he claims will hold 9 to 10 tons of gravel that I can probably hire for a couple of days to run back and forth much cheaper than renting a vibratory compactor.

 

[bigtiller]

Is there another "dirt guy" in the area? One with newer equipment and older employees might have the tools and experience to help you better than your first choice guy can.

 

[FentonFarmer]

If I could chip in with a few things from the other side of the world. Here in Australia my family have just completed a new house build on cut and fill. I have just punched some numbers into the metricator and we did over 50,000 square feet of cut and fill up, up to about 6foot high in places. We had a couple of contractors quote us with different sized machinery (it was to big a job for the 5035 Mahindra) Many insisted that track rolling by excavator and truck compression would be enough. In the end we went for a fantastic older contractor who gave us what I thought was very good advice.

The slab and building are only as good as what they are built on. For us it was reactive soil that needs lots of work to be stable. So it was worth putting some time and money into the base. Especially as we plan on staying for quite a while. The barn might have lower requirement than a home but I believe the principle is the same.

Tracked machines are really good at minimising their ground pressure and maximising their traction. If they track roll a site it comes up smooth but the deep compaction is quite minimal in comparison to specialist gear. The padfoot roller really only has one function and did it well for us.

Like many things the secret is a good recipe. The Mahindra did get a run on site as the tow vehicle for the 260 gallon water trailer. We used a fire pump and 2inch hose to spray the clay down and keep a wet texture. We would spray out before the dozer added a clay layer and spray as the roller worked. We tried to maintain a level of moisture like a bread dough where you could squeeze a ball in your hand and it held its form without being dripping wet. We only ever added about 6-8 inches in any one pass with the dozer. In hindsight for us this was a key. The layers bonded really well and later when we augered post holes and house pilings you could see and hear how strong the layers were as a whole or hole in this case.

We paid about$120 an hour for our roller on site. It sounds expensive next to your day rate but we only paid for machine hours. So when we had one operator on site our bill was broken down into so many hours bulldozer@$140, 20ton excavator @$135ph and roller. No operator wanted to be onboard the roller for hours. A water truck was supposed to be nearly $90ph and so the mahindra came through big. It worked out well until we had to pick up time and ran three operators. Impressive amount of soil gets moved, but every tick of the watch is accompanied by the sigh of a bank account crying.

Not sure I have helped with the decision making but I hope some info helps. For us it added to the cost to do it with the roller but the extra cost as a percentage of our house build was worth it to know we had the best prepared base under our home. Especially given how reactive our soils can be. As it turns out we have had our annual rainfall total in five months this year with winter not yet here so we will soon know it was worth it.

I threw in a pic to give you an idea of the scope of our fill

Good luck with the build, I love a good barn or as we call them Shed.
Cheers,
B.R

 

[Egon]

The compactor type depends on the soil being compacted. For clay a sheep’s type works best ( it could have a vibratory function) compaction should be continuous as the soil is being laid down. This prevents laminated layer and makes for a solid mass. The dirt, rolled between your palms should for a string at a good compaction moisture content. When the sheep foot walks out you usually have the proper compaction. Granular material spread on top require a smooth roller or plate vibratory packer. A rubber tired packer would also work.

 

[Hay Dude]

Whats the big deal? Just rent a remote control ram max machine with sheep foot rollers and run it back and forth.
Cheap and so easy you can sit in a lawn chair and run the thing with a cold drink.

Skipperbrown, that price is outrageous. You or one of the contractors helpers can do this for 1/3 that price he quoted you.

 

[EddieWalker]

If I could chip in with a few things from the other side of the world. Here in Australia my family have just completed a new house build on cut and fill. I have just punched some numbers into the metricator and we did over 50,000 square feet of cut and fill up, up to about 6foot high in places. We had a couple of contractors quote us with different sized machinery (it was to big a job for the 5035 Mahindra) Many insisted that track rolling by excavator and truck compression would be enough. In the end we went for a fantastic older contractor who gave us what I thought was very good advice.

The slab and building are only as good as what they are built on. For us it was reactive soil that needs lots of work to be stable. So it was worth putting some time and money into the base. Especially as we plan on staying for quite a while. The barn might have lower requirement than a home but I believe the principle is the same.

Tracked machines are really good at minimising their ground pressure and maximising their traction. If they track roll a site it comes up smooth but the deep compaction is quite minimal in comparison to specialist gear. The padfoot roller really only has one function and did it well for us.

Like many things the secret is a good recipe. The Mahindra did get a run on site as the tow vehicle for the 260 gallon water trailer. We used a fire pump and 2inch hose to spray the clay down and keep a wet texture. We would spray out before the dozer added a clay layer and spray as the roller worked. We tried to maintain a level of moisture like a bread dough where you could squeeze a ball in your hand and it held its form without being dripping wet. We only ever added about 6-8 inches in any one pass with the dozer. In hindsight for us this was a key. The layers bonded really well and later when we augered post holes and house pilings you could see and hear how strong the layers were as a whole or hole in this case.

We paid about$120 an hour for our roller on site. It sounds expensive next to your day rate but we only paid for machine hours. So when we had one operator on site our bill was broken down into so many hours bulldozer@$140, 20ton excavator @$135ph and roller. No operator wanted to be onboard the roller for hours. A water truck was supposed to be nearly $90ph and so the mahindra came through big. It worked out well until we had to pick up time and ran three operators. Impressive amount of soil gets moved, but every tick of the watch is accompanied by the sigh of a bank account crying.

Not sure I have helped with the decision making but I hope some info helps. For us it added to the cost to do it with the roller but the extra cost as a percentage of our house build was worth it to know we had the best prepared base under our home. Especially given how reactive our soils can be. As it turns out we have had our annual rainfall total in five months this year with winter not yet here so we will soon know it was worth it.

I threw in a pic to give you an idea of the scope of our fill

Good luck with the build, I love a good barn or as we call them Shed.
Cheers,
B.RView attachment 656942

You found the right contractor. He did it right and you wont have any issues with your foundation!!!

 

[BrokenTrack]

A bulldozer will be fine.

I was putting in a road on my farm, and my Grandfather was backing the truck up, and he would go about 5 feet and then drop out of sight. After a few loads he got out of the truck and asked me how I was spreading the gravel, and I said using the excavator.

"no, no, no", he said, "Use the bulldozer, and use the tracks. Flatten the load with the blade then get in there and steer, steer, steer." The tracks grousers lock those rocks together and compact it like you would not believe.

The next load, he backed his truck all the way to the end of the gravel he had just dumped. I would not have believed my grandfather if I had not seen it myself.

Here in town, his roads have lasted 40 years. Roads where they have used excavator and sheeps-foot roller have only lasted 10 years before breaking up. Trust your contractor, he knows what he is doing.