High Stability Stake

Depends on the soil. You might try a 4 foot 3/4 rebar. If you want it really stiff find some of the 100 ksi stuff. You might want to sharpen the end and make sure you don't drive it into any utilities. I use 24 and 30 inch 5/8 rebar for boundary markers.

A dozer will make short work of a 4' rebar, regardless of the diameter. I think your best bet is to get the contractor to properly prepare and stabilize the site before you stake.

> What is something I could set to a gnat's whisker that wont move?

Nothing, just ask the NGS. 🙂

These make for a pretty stable monument and are relatively easy to set:
http://www.berntsen.com/Surveying/Survey-Monuments/FENO-Survey-Monument

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> These make for a pretty stable monument and are relatively easy to set:
> http://www.berntsen.com/Surveying/Survey-Monuments/FENO-Survey-Monument

These are good at what they do, but I wouldn't consider them for construction stakes. They're expensive, and though relatively easy to set compared to a dug-in pipe or concrete monument, it's still a multi-step operation that takes a lot more time than slamming in a hub or rebar.

I've set a dozen or so of the 1-meter variety, and in my experience the horizontal stability is just okay. Because the point is slightly larger in diameter than the shaft, there's a bit of wobble left after setting unless you pack the dirt around it, and that's not something you want to do if you're trying to set something at a precise location and have it stay there.

I like them mostly for their vertical stability. The prongs, once deployed, keep the mark from sinking or lifting with respect to the earth layer in which they're set.

They're also very, very hard to remove; you pretty much have to dig them all the way out once the prongs are deployed. While that wouldn't prevent someone from disturbing one, they'd probably not bother trying to root out more than one unless they have a backhoe.

Thanks for the ideas. Maybe I need to have them roll the pad a couple extra times to tighten it up. Unfortunately it sounds like I'm going to have to restake and adjust any bad hubs over and over and over again.

The Feno markers look cool but I can't see setting 38 of them for column lines. I think it would be too costly and time consuming.

Even the fenos move vertically in freeze/thaw cycles. If the exterior footings/walls are poured you can try to get marks on them to at least let people verify the stakes are not moved. We have used 4' rebar before and used a large rebar saftey cap to put the mark on. You could try batter boards. It always seems simple to layout column lines but when you get down to the nuts and bolts of it isn't it better for us as surveyors to provide layout for each column. I know the contractors always precive that it's going to cost them a lot of money but the crew time they save shooting the lines themselves would typically make up the cost. This is just my opinion though.

> Even the fenos move vertically in freeze/thaw cycles.

Yes, I expect they would. I sometimes forget that not everyone lives in a place where temps below 40 are rare, and ground freezing is nonexistent.

On a Sears building back in 1975 we put in a fenced and cross braced batter board of 4/4, 2/6 and 2/4 around the building and left an entrance for the concrete truck and other vehicles to pass thru.

There were form nails on centerline of all bolt patterns and the top of boards were a set distance above column grade. On the side of the boards everything was numbered and lettered just like on the plans.

It was mostly not disturbed and was convenient for carpenters to pull strings and rough in a column box and bolt patterns.

While they were busy digging holes, building rebar cages and forms we could be doing something somewhere else.

Once they had enough boxes built to call in a truck load of concrete we arrived and setup made final alignment and elevation checks on the bolt plates as they were nailed in place and wired to the rebar frame.

After the concrete cured we would come back and set the elevation of the bottom nut for the steel to be set in place and let the riggers get to work.

Bottom line is that you have to have your control outside of the workzone so you can transfer it quickly and easily to one specific location.

In the late 1980s we would have two EDMs setup on two different control points and radial stake to the same point as a double check. Depending upon the critical importance of the location, we would have a level setup nearby for the doubters.

Today, a robot would probably be the way to go.

[sarcasm]Those darn big yellow machines with tracks, blades and buckets can disrupt most anything you try to do.[/sarcasm]

I totally agree about setting the control outside of the work zone. I have 5/8" rebar set all around site from the second closed loop traverse I ran at the beginning just after the clearing was completed. I set all of them outside of the silt fence with pig-pen lath around them. One benefit of having run the closed loop is that each setup point will have at least two points that are visible from it so you can take a backsight and then turn the angle and check into another point. In some places I can still see across site, but that will change as more crap gets piled up.

I've been pleasantly surprised at how stable these have remained. We've had a very cold winter with a lot of frost and I've seen little to no frost heave as of yet. We will see what happens when it warms up. Hopefully they wont sink.

I am not providing grades on the column line stakes, so they are really just for horizontal reference. I will probable end up setting 2-3 benchmarks around the building for elevation when time comes to pour concrete.

Yup, you gotta go off site, just take a look at what deformation survey crews do.

Dan--Awhile ago probably before you where born was involved in the construction of a major building. We decided to set monuments on the two lines of the longest anchor bolt lines. They were set on line in a landscape area or behind the curb or somewhere they wouldn't be disturbed. Have to look at the proposed site plan to figure that out. At least you would have two parallel lines to work off of. Even if the are within the work area batterboard the he!! out of them so those big yellow things stay away. Is the job in the Republic of South Jersey? and sandy conditions? You have worked on enough jobs and know that the closer you get the closer the mason, carpenter, etc gets. You've seen enough with me of "wow these bolts are pretty good" and the other end of "WTF" there's only 24 sets and 12 are out. All depends on the practices of the contractor on how he sets them and you have no control over that. Good Luck and stay warm.

Mazoo

Thanks, Steve. These stakes are going to be in the middle of the site. I'm kind of hesitant to use monuments. Yes, it's in the People's Republic of South Jersey. The soil is sandy and looks pretty much like bank run. (It's a shame the gub'ment owns it, because it would be ideal for residential construction with septic systems.)

These guys do very good work. They get within a couple hundredths of what I stakeout with utility stuff, so I can't wait to see what they do with the anchor bolts.

The problem is that they need the column lines really accurate to run utilities into the building under the future footing elevation and come up in precisely the right spot. That's what they will be using the stakes for initially. I'm guessing I will re-stake them again just before they get ready to pour concrete and set the bolts.

I helped layout a $585,000,000 silicon plant in SW MT. I spent 2.5 years most of it 6-10hr days on the project. I found out that when equipment is working nearby every type on stake/rebar moves to some extent. Worst day I recall it was raining so hard we had to set four pointed 2x4's 4 ft long side by side to help hold 1 hub tack point in the super saturated soils Almost half of our time was spent re-setting control and layout; tolerances were 0.01':pinch: for all anchor bolts. The site elevation bench was a nail in a power pole and it went down 0.04' sometime during the second winter:pissed:

Sounds like a nightmare! Your 2x4 comment reminds me of the time I set a 2x4 for a curb stake because there was so much mud. The instrument man laughed and remarked that I looked like He-Man driving a 5' long 2x4 into the ground so easily with a 4lb short handled sledge! It tightened up at the bottom and I set a tack. (I think it was a radius point.) I doubt the curb held up very well :'(

[sarcasm]Helical pile.[/sarcasm]

We run across this daily. Run a box around your column lines and range them out as far as possible. Don't walk by a piece of concrete without leaving a red pencil mark. Set your hubs on line and range them out off site. Set up on the hub and "buck in" both ways. Might be on the tack, might not. Sight longest line and turn 90. Mark the bolts. Setup on perpendicular line and do the same. Repeat process and set you line. Check it with a square. Maybe steel tape between patterns. Do it again after they pour. We don't do radial layout.

The best I've found were setting control on top of the test piles, after the tests have been run. Usually they test to failure, so they aren't going to be used as part of the building itself. While no longer fit to put a 120 ton load upon, they tend to remain stable throughout the project.

As was said above, off site control doesn't have to be particularly elaborate, typically use 24" 5/8" rebar set flush. If possible, will pour a sleeved collar around it but that is about it. And more offsite control is better, can't name the number of times the ones I thought would be primary became unusable due to someone's laydown area.

The past few years I've had to resort to resections more than I like. I've found while time consuming, a minimum 4 point resection is warm and fuzzy capable. Working solo that can be problematic, as about the time I start an observation, someone needs to put a porto-let right on line.