How long do hubs last....

i always make a plan with the stakes i've set out and send the signed plan to the contractor.

I also take photographs of every hub with some reference points.

I always ask when they are goning to use the hubs and set them out only days in advance (if it is possible).

If it is an area with a lot of activity but not much cut or fill, I like to use rebar instead of hubs and keep the top down 4-6 inches from the surface. They seem to be more stable.

I've recently been treated to an example myself. I set out grid control for an industrial building a couple weeks ago. One side was an existing building that is being added onto. On that side I set stickers on the wall. The other 3 sides were hubs, set to gnat's a__. Day before yesterday I was out to set tacks in batterboards and a few additional hubs. The stickers all checked <0.01'. The hubs were all +/-0.03'. Instrument position was resected from control well outside the hole in both cases.

So, yes. I absolutely believe that hubs move in the presence of large machinery.

JaRo, post: 378914, member: 292 wrote: If it is an area with a lot of activity but not much cut or fill, I like to use rebar instead of hubs and keep the top down 4-6 inches from the surface. They seem to be more stable.

Seems like it would be hard to set a rebar to the nearest 0.01'. Do you have a punch hole in the top of it or something? This is for steel construction where the columns end up being partially exposed and the finish material has to line up perfect. I've been told 1/4" error is out of tolerance for those reasons. I am actually going back out later today to check the anchor bolts before the pour so they can tweak them if necessary...

I don't think hubs were really ever meant to be that permanent. And their functional brevity is probably more fragile than we're willing to admit. I've seen 8" hubs get displaced horizontally with just a loader rolling past it at a distance of a foot or so...and we all know what happens vertically to that hub when the loader rolls over the top...Bottom line, you can't trust them to last too long and everybody should know that.

One project I remember having a lot of trouble due to equipment and such. We settled with 24" 2x4s, cut sharp on the bottom by the Carpenter's Local. We drove them in with an 8 pound and left them sticking up about 4". Then tacked them with a precise point. To paraphrase Crocodile Dundee, "Now that's a hub!"

Dan Patterson, post: 378917, member: 1179 wrote: Seems like it would be hard to set a rebar to the nearest 0.01'. Do you have a punch hole in the top of it or something?

I use 3/4 rebar with a rod bubble on the side while driving it to keep it vertical and then punch the top. Usually it only has to be dead on for one direction. If I know it will be a hard drive, I will set a hub and tack, then put a tripod and tribrach on it high as I can. Pull the hub and drive the rebar watching it as it goes down. If you hit the tripod, then you get to start over.

James

Wow! That is quite an effort for a survey stake!

Although, there was one project where I got 6' lengths of unistrut from the electricians, drove them into the ground with a post driver and then sledge, cut the mangled top off with a gas saw, bolted on a metal top plate with two spring bolts, and then screwed a piece of plywood onto that with those stinger screws. Then I set a tack in the plywood. I think I set about a dozen of those around the building. Then whenever I checked I could just pluck out the tack and move it over if it had moved, which it usually had not. (I think I moved two of them twice).

Most of the work I had used them on were bridges. Two points on centerline and two points for each abutment/bent. Mostly centerline because of access, the points on the side could usually be set on 12" hubs at the R/W and be out of the way.

How do you guys set points for grid lines? Radial stakeout? With a rod? I think staking radially, even with a mini prism, there always seems to be a hundredth or two...or threeo_O floating around.

Jim_H, post: 378928, member: 11536 wrote: How do you guys set points for grid lines? Radial stakeout? With a rod? I think staking radially, even with a mini prism, there always seems to be a hundredth or two...or threeo_O floating around.

I know a lot of guys swear by radial layout these days but we like to set the (3) major offset corners, and then occupy the corner, shoot the long backsight and check into the 3rd. if everything looks good we set the fourth overall corner. Then we can occupy the main corners and sight right along the lines where the offset stakes will be set as shown as points 127, 130, 138 & 141 on the attached PDF.

Nothing more embarrassing than a contractor setting up his transit and asking why those points don't line up, even if is only a little.
We typically stake buildings like this with a mini prism and plumb bob or a mini prism with a short pole to minimize error.

Little more effort than radial but we do not hear any complaints and the check are always tight. Plus you make sure you charge accordingly for the time it takes and not provide a lower price since you are going to stake it radially.

I'm just one guy with a robot, so I would reap no benefit from the non-radial layout method. That being said, all my tripod screws are tight, I calibrate my prism pole bubbles, make tight setups and use a bipod for layout. I have not had those complaints, but you have to evaluate your overall measuring system which consists of everything from the robot to the prism pole point. The average field guy probably doesn't care enough or know enough (some do, but most probably don't) to consider all those factors though, so I see where you're coming from.

Dan Patterson, post: 378947, member: 1179 wrote: I'm just one guy with a robot, so I would reap no benefit from the non-radial layout method. That being said, all my tripod screws are tight, I calibrate my prism pole bubbles, make tight setups and use a bipod for layout. I have not had those complaints, but you have to evaluate your overall measuring system which consists of everything from the robot to the prism pole point. The average field guy probably doesn't care enough or know enough (some do, but most probably don't) to consider all those factors though, so I see where you're coming from.

I hear ya Dan, and some guys I know get awesome results radially. I still like to approach these the way we do since we typically have two guys doing this and it works for us especially on these larger buildings.
Of course what doesn't help is when the super calls and says " you didn't need those overall corners any longer did you"

It all moves. Check, and recheck is your only friend or RP's out of harms way.

On a non-construction related note. I just recently found 3 out of 4 hubs set online in 1988 in the dark, damp brush of the pacific northwest. One was merely a hole ringed in Flagging but the others were slightly rounded stobs of wood ringed in flagging. On the Eastern dryer side of our state one may find that the wood can last many decades.

My dad taught me, many many moons ago, have a VERY stable network that is visible, but not onsite. Always return to it and check into what you need to work off of.

So far, it hasn't let me down. That would be my recommendation is that you come in, every time, off of the stable control and do what you need and check in early and often.

Dan Patterson, post: 378903, member: 1179 wrote: ...on a construction site?

24 hours, Re-staking is gravy money. 😉

Gregg Gaffney, post: 378938, member: 1111 wrote: I know a lot of guys swear by radial layout these days but we like to set the (3) major offset corners, and then occupy the corner, shoot the long backsight and check into the 3rd. if everything looks good we set the fourth overall corner. Then we can occupy the main corners and sight right along the lines where the offset stakes will be set as shown as points 127, 130, 138 & 141 on the attached PDF.

Nothing more embarrassing than a contractor setting up his transit and asking why those points don't line up, even if is only a little.
We typically stake buildings like this with a mini prism and plumb bob or a mini prism with a short pole to minimize error.

Little more effort than radial but we do not hear any complaints and the check are always tight. Plus you make sure you charge accordingly for the time it takes and not provide a lower price since you are going to stake it radially.

We use this method for buildings with structural steel and/or prefab components. If it's a slab on grade with stick frame above we'll do it radially. For each we use a shorty rod though. For the close ones adjacent to the 10x10 box corner offsets we'll set line with the gun but pull the distance with a steel tape. Just like mentioned above with the contractor sighting down your line, nothing worse then having them throw a tape down and being off 0.03'.

I was blessed to work construction long enough to know when to set stuff radially and when to get on-line to stake points. My money says there are good supers and tradesman who 'fix' a lot of radially staked work where necessary and the surveyor never knows. Control is important for repeatability, but often constructability is relative.

'Fix' a few points with the robot and check them with your tape minutes later instead of hours or days.

Steve

Wait a minute. They're supposed to last??? Maybe a couple hundred feet outside of the general construction zone. Anything closer is a target for trouble.

i have set hubs for what you describe, walked away from said, hub, only to see an excavator roll past it with in 4 micrometers...all the while the operator smiling probably because he was proud of himself for not rolling over the point, so ti must still be good.