Field Engineer Guide To Going Up The Building (Vertical Control Transfer In Construction)

Field Engineer Guide to Going Up the Building (Vertical Control Transfer in Construction)

I’m excited about this topic because this is a huge topic, and it gets done wrong all the time, and we’ve got to get back to doing it the right way if we’re ever going to be successful. What I’m talking about is bringing up horizontal and vertical control up the building.

The San Diego High-Rise Story: 2.5 Inches Off

Let me start by telling you a story. There was a massive high-rise in San Diego, and we actually had inside intersecting baselines, which worked out great. All of the control worked out beautifully all the way up through five floors. And I’m not trying to blame somebody else. This is just telling the story accurately. I never want to become that guy that’s embellishing on story, so I got to keep it accurate.

So, I got done training the group, and they went back up to L.A., where I spent most of my time, and they got up to levels seven and eight and called, and they’re like, “Jason, we’re out of whack. Things are not lining up.” So, you know with post tension that it will compress and deform the decks, right? It’ll like wrench the decks, and it will skew. Whenever we scan the decks, it’s interesting to see what they do. Sometimes the decks literally shrink from side to side. They will actually skew. They do all kinds of weird things.

And so, after a couple of floors, the control, because they were going from floor to floor, came in by up to 2 and a half inches, and they were in big trouble. And I was like, “Hey homies, we have got to always plumb down to the first level.”

The Backup Check: Sight from Bottom to Top

And then I also gave them a backup. I said, “Let’s say something’s in the way of your sleeve. You can set up out here and sight down here at the bottom and then rake it up and check the edges of the decks once you have your control. And you can do that on all four sides if you want to.”

But the primary method of going up the building is through sleeves.

The Best Way: Plumb Through Sleeves to Ground Floor

When you have your base level, I want grid systems on here to where we can take two points. And then when we do the upper floors, I can literally plumb up through a sleeve. That’s going to go all the way up. And then when I’m on this upper floor, I can establish these same grid lines. And these same grid lines should match up on the edges. So, if you are sighted, you could sight the bottom and sight up, and it will match.

The point is, if you’re up here on these upper levels and you’ve got these two sleeves, you’ve got to plumb all the way back down here to the base. You got to plumb all the way back down here at the base. Otherwise, it will drift. You can’t go from floor to floor and compound. And yes, you can have these outside double checks, but this is the best way to plumb up through a structure.

Elevator Shaft Plumbing: The Tattletale Concept

There’s also ways, like you know in concrete they use tattletales, where you have formwork and they will have a certain offset, and they will let a string fall either to adobe or a plumb bob or a bolt or something that weighs it down, and they know what the offset is. So down at the bottom, they will literally measure how far that string is off of the face of the form, and so they know if it’s plumb, right?

That kind of concept inside of an elevator shaft. I like to have inside the inner decking formwork of that core openings to where you can plumb all the way from the base all the way up that elevator shaft and make sure that that core is plumb so that it will accommodate the guide rails for the elevators.

The Best Way to Bring Up Elevations: Chain Up Tower Crane or Steel Columns

The other thing that I want to talk to you about is bringing up elevations. Now, you could come up here and put your level rod through the hole and do a level loop on the floor and establish benchmarks. But my favorite way of doing it is to find a way to chain up the side of the building or chain up through a core or if it’s a steel structure, chain up on the outside of a column.

And my favorite thing to do, and you all will think I’m crazy, but everywhere I’ve done this, it’s worked out great, is to chain up through the tower crane. Now, tower cranes do move, but it’s not enough when you calculate the movement to where it’s going to be very much difference in the vertical distance.

So, the tower crane, let’s say that’s a 4-foot offset above finish floor. I’ll just literally use a calibrated chain and mark that 4-foot offset all the way up the building. That’s the best way to do it. But you can’t again take measurements from floor to floor, floor to floor, floor to floor, floor to floor, floor to floor and not expect there to be some massive elevation problems.

The best way is to simply chain up the tower crane, chain up the vertical steel column, chain up the core, or chain up the side of the building to the edge of the decks in a proper manner. And when you’re using the chain, you got to make sure you’re not going to have sag if you’re doing it vertically. But I’m going to say no sag. You’ve got to adjust for temperature. And you’ve got to make sure that you have the right tension.

Critical Chain Usage Rules: Tension, Temperature, No Sag

I looked recently, Brandon Montero and I looked, actually Kate Schroeder and I looked, we used to have those little tension handles for fish, you know, you just hang a fish off of it. They still sell those. Chaining clamps are hard to find nowadays.

But the bottom line is if that chain, that steel certified calibrated chain, that steel tape says you need to have 20 pounds of tension, you better have 20 pounds of tension, especially if you’re chaining vertically.

Here’s the vertical control process:

• Plumb through sleeves to ground floor (never floor to floor) – When you have base level, want grid systems to where we can take two points. When we do upper floors, plumb up through sleeve going all the way up. On upper floor, establish same grid lines. If you’re up on upper levels with two sleeves, plumb all the way back down to base. Otherwise, it will drift. Can’t go floor to floor and compound. This is best way to plumb up through structure.
• Backup check: sight from bottom to top – If something’s in way of sleeve, set up out here and sight down at bottom, rake it up and check edges of decks once you have control. Can do that on all four sides if want to. Outside double checks available but primary method is through sleeves.
• Elevator shaft plumbing: tattletale concept – Use tattletales where you have formwork with certain offset. Let string fall to adobe or plumb bob or bolt that weighs it down, know what offset is. Down at bottom, measure how far string is off face of form, know if it’s plumb. Inside elevator shaft, have inner decking formwork of core openings to plumb all the way from base all the way up elevator shaft. Make sure core is plumb to accommodate guide rails for elevators.
• Chain up tower crane or steel columns for elevations – Favorite way: find way to chain up side of building, chain up through core, or if steel structure, chain up outside of column. Favorite thing: chain up through tower crane. Tower cranes do move, but not enough when calculate movement to be very much difference in vertical distance. Tower crane 4-foot offset above finish floor: use calibrated chain and mark 4-foot offset all the way up building. Best way.
• Chain usage rules: 20 lbs tension, temperature adjustment, no sag – When using chain, make sure not going to have sag if doing it vertically. No sag. Adjust for temperature. Make sure have right tension. If steel certified calibrated chain says need 20 lbs tension, better have 20 lbs tension, especially if chaining vertically. If using steel, adjust for temperature because buildings before conditioned expand and contract.

If your project needs superintendent coaching, project support, or leadership development, Elevate Construction can help your field teams stabilize, schedule, and flow.

Why Post-Tension Decks Drift: Compression and Deformation

You know with post tension that it will compress and deform the decks. It’ll wrench the decks, and it will skew. Whenever we scan the decks, it’s interesting to see what they do. Sometimes the decks literally shrink from side to side. They will actually skew. They do all kinds of weird things.

And so after a couple of floors in San Diego, the control, because they were going from floor to floor, came in by up to 2 and a half inches. That’s why you’ve got to plumb all the way back down to the first level. Otherwise, it will drift.

A Challenge for Field Engineers

Here’s what I want you to do this week. Set up your vertical control properly. When you have base level, want grid systems to where you can take two points. Plumb up through sleeves going all the way up. On upper levels with two sleeves, plumb all the way back down to base. Never go floor to floor. Otherwise it will drift.

For elevations, chain up tower crane, chain up vertical steel column, chain up core, or chain up side of building to edge of decks. Use calibrated chain with 20 pounds tension. Adjust for temperature. No sag. Mark 4-foot offset all the way up building. If something’s in way of sleeve, set up outside and sight down at bottom, rake it up and check edges of decks. Can do that on all four sides for backup check.

Never, ever, ever go from floor to floor, floor to floor, floor to floor for either horizontal or vertical control. That’s how you end up 2.5 inches off like the San Diego high-rise. As we say at Elevate, vertical control for field engineers: plumb through sleeves to ground floor, never floor to floor. Chain up tower crane or steel columns for elevations.

On we go.

Frequently Asked Questions

Why never go floor to floor for vertical control?

Because post tension compresses and deforms decks. It wrenches decks and they skew. Sometimes decks literally shrink from side to side. After couple floors in San Diego, control came in by up to 2.5 inches because they went floor to floor. Must plumb to ground floor.

What’s the best way to plumb up through a structure?

Through sleeves. When you have base level, take two points. Plumb up through sleeve going all the way up. On upper levels with two sleeves, plumb all the way back down to base. Otherwise, it will drift. This is best way.

How do you chain up for elevations?

Chain up tower crane, vertical steel column, core, or side of building to edge of decks. Use calibrated chain with 20 pounds tension. Adjust for temperature. No sag. Mark 4-foot offset all the way up building. Best way.

What’s the backup check if something’s in way of sleeve?

Set up outside and sight down at bottom, rake it up and check edges of decks once you have control. Can do that on all four sides. Outside double checks available but primary method is through sleeves.

How do you plumb elevator shafts?

Use tattletale concept. Have formwork with certain offset. Let string fall to plumb bob or bolt that weighs it down. Down at bottom, measure how far string is off face of form, know if it’s plumb. Makes sure core plumb to accommodate guide rails.