Final grade for a building pad

[bam1968]

A local farmer is building a new shop and I am helping them with the building pad. The building is 120' x 150'. The concrete guy wants it to be level within 1/2". After being told that and picking my chin up off the ground the building Rep said if we can get it within 2" that would be plenty good enough. I should note, the building will be sitting on all cut dirt. Currently, we are about 1 ft above grade. I am trying to figure out the best way to establish the final grade. One option is I have a blade mount laser receiver for my dozers but my smallest dozer is a D65 Komatsu with a 4 way blade. Another option is.... The farmer has 2 tractors that are pulling scrapers with some sort of gps on them that tells its elevation and seems to be pretty accurate according to some shots I have taken with my laser and then compared it to there gps readings. I am just trying to figure out what would be the best way to come up with final grade. Any and all input will be greatly appreciated. Thanks

 

[lumberjack]

It sounds like you're the only person doing dirt work? +/-2" is a huge variance and will add a heap of expense in concrete to make up the difference if no one is coming in behind you to tighten it up.



As far as the best way of doing it, I'm no dozer hand, but I would think a dozer could handle that tolerance with an experienced operator and some stakes or grade man. I don't do much dirt work but back in 2013 we hauled in 8k yards of dirt for a large house pad. We built the pad higher and got our final compaction, then cut it down to grade with a guy holding the grade rod to give me references. We did the whole job with a CTL. Of course after we got the pad to grade, other contractors came in and tore the grade all to bits... par for the course.

 

[Scrub Puller]

Yair . . .

bam1968. Bloody hell mate concrete must be cheap in your area if you are going to work to two inches!!!

Depends on the dirt of course but if I was doing it for myself I'd peg it every twenty feet, aim to undercut it slightly, then bring in sand, and with stringlines, screed it off exact . . . concrete here is over three hundred bucks a cubic metre . . . been quoted double that in some places that I've worked.

Cheers.

 

[Shimmy1]

The concrete guy wants is level to within a 1/2". After being told that and picking my chin up off the ground the building Rep said if we can get it within 2" that would be plenty good enough. I should note, the building will be sitting on all cut dirt.

WHAT, you've never graded a building site before?? :drinkup They are going to bring in at least a few inches of class 5 for subgrade I would hope?? They just want their job to be as easy as possible. It's a whole lot easier screeding gravel out level on a relatively true pad vs. a trainwreck. That being said, if you have a laser and a machine receiver, you should be in business. The dozer could definitely do it, it'll just take a bit and a steady hand. Would be WAY easier with the scraper. Do either of the scrapers have a mast? If not, before I had my hydraulic mast (when I still used the laser on my scraper)I used a magnetic hoe mount on the side of the scraper a few times. Worst case, you'll have to do it by foot, walking behind the scraper checking grade with the rod. On a pad that size, it's about 80 yds³ per inch of compacted fill, so if gravel is hard to come by they might get excited. However, I'm sure it's not $135/yard, which is what delivered mud is here.

 

[RBMcCloskey]

Keep this in mind; 120 x 150 = 18,000 sf. x 0.17 / 27 = 113.34 cy of concrete @ $130. CY = $14,735.

Using your equipment get it within 2" and compact it to density, you cannot fine grade loose material.

Call your Caterpillar dealer and find out who has a motor grader with a laser system you can hire should take 2 days.

I am sure you can get the grader and a operator for less than $14,000.

 

[bam1968]

Thanks guys. Its not my first pad but it is the biggest. None of the scrapers have a mast. I met this morning with the owner, concrete guy and building rep and now feel a lot better about things. The concrete guy was very happy with the way things looked. I think I'm going to use the laser and receiver on the dozer as it seems the gps (which is only mounted on the tractors) seems to be a little inconsistent for some reason. They are going to put 2" of gravel subgrade in which is readily available here.

 

[Hoppsxc140]

Rough it in with the scrapers GPS, finish with the laser on the dozer. Should be a two day job. 670 Cy coming out, 20 yard scrapers, 33 loads out, 16.5 loads each. If its a half hour cycle they will be done in 8 hours. Follow behind with the dozer as they cut to clean it up. Second day haul in the 210 tons and grade with dozer.

 

[CM1995]

Yair . . .

bam1968. Bloody hell mate concrete must be cheap in your area if you are going to work to two inches!!!

Depends on the dirt of course but if I was doing it for myself I'd peg it every twenty feet, aim to undercut it slightly, then bring in sand, and with stringlines, screed it off exact . . . concrete here is over three hundred bucks a cubic metre . . . been quoted double that in some places that I've worked.

Cheers.

$300 bucks a cubic meter! Wow that's expensive. The last mud I ordered was $105 a cubic yard, delivered taxes and all. We have cheap concrete prices since we're smack dab in the middle of limestone country with sand 40 miles away and fly ash from the cement kilns.

Bam1968 it sounds like your on the right path. 120x150 is not that big of a pad if you have to put in hubs and blue tops. My contracts have final grade +/- .10' which is easy to obtain with a little finish work.

Will you be placing the rock or the concrete sub?

 

[td25c]

We still drive down grade stakes on corners of the pad and one in the center & work off that on first phase with dozer .

Second phase set up transit and drop paint on the ground showing high spots that need cut yet . Might just look like ( - 3 or -1 ) in various spots .

You guy's do know how to swipe off an inch or so of grade on hard pan clay easy with a dozer ?


Under cut it all then build back with stone of choice .

My all time favorite fine grade tool is farm tractor & box blade combo .

Prepped a cell tower site with the Allis 175 .
https://www.heavyequipmentforums.com/showthread.php?14619-Box-blade&p=186498&viewfull=1#post186498

We keep it pretty simple .

 

[Scrub Puller]

Yair . . .

CM1995

$300 bucks a cubic meter! Wow that's expensive.

Some of the outfits are very proud of their concrete. (big grin)

In remote areas it can get seriously expensive as you are talking delivery trips of several hundred miles.

One bloke told me he had a contract to erect road signs and was quoted a thousand bucks a meter. B/S of course for road sign footings but he wasn't allowed to hand mix as the mud had to be "certified and from a recognised supplier" or words to that effect.

As an aside I saw a couple of days ago a news item about Aboriginal housing in remote areas and the Government wallah said with a straight face that concrete costs of over one thousand dollars per meter were one of the reasons it was so expensive. . . . sheesh.

Cheers.

 

[Queenslander]

We've just paid $305 for 32mpa delivered over 70 miles, which is just not too bad, sure beats mixing it yourself.

 

[Scrub Puller]

Yair . . .

Gotcha Queenslander. I saw the picture you posted on lifting trusses and I reckoned there would be a bit of concrete involved . . .nice looking shed.

Cheers.

 

[bam1968]

Thanks again. They will be using a rock subgrade. I should have took some pics but we cut a hill down @ 12 ft to get to the elevation they wanted. The owner, who was running one scraper, wanted the building to sit on 'virgin ground'. We basically cut it down to about 6" above grade then did like td25c mentioned and parked one scraper and had that guy just shoot grade and paint how much we needed to cut on the ground until we got down to 1-2" above grade. Then we just used one scraper mainly because the other scrapers had a lower center cutting bit on them. We did get it within 1/2". Since then we have gotten @ 5 inches of rain. Other than one little puddle @ 1" deep and @ 4' in diameter the rest of the pad was high and dry.