Working Control For Field Engineers (How To Set Layout Points In Construction)

Working Control for Field Engineers (How to Set Layout Points in Construction)

In this blog, I’m going to talk to you about the difference between working control and secondary and primary control and some of the things that you really need to look out for when you are designing it.

The Three Types of Control Networks

We know that primary control is a control network that is precise and accurate that surrounds the project site, that is permanent. And that secondary control is building specific and it’s semi-permanent. And that working control is where once you have grid lines and you need to lay out a wall line, you can lay out that wall line and that’s called working control.

What Is Working Control? (Component-Specific and Temporary)

So let me just go ahead and zoom in a little bit. Like, let’s say that this is your slab on grade. I’m just using general terms here and general examples. Let’s say that my grid lines are right there and I have this wall that I want to build and the carpenters asked for a 3-foot offset line and they want to make sure that there’s an elevation temporary benchmark over here. That right there is working control.

Now, grid lines are technically still secondary, but let me give you some guidelines here.

The Wrong Way to Establish Offsets (Don’t Do This)

When you are taking a foundation plan and a slab-on-grade plan, and you’re going to transfer your baseline, which can technically be on grid line perfectly or at an offset, I’m going to do offsets.

Let me just do this the wrong way and then I’ll show you the right way. Let’s say that somebody was like, “Okay, I’ll do an offset in this direction, and then I’ll do an offset in this direction, and then I’ll do an offset in this direction, and then an offset in this direction, and then offset in this direction.” We’re going to confuse somebody, and we’re going to get something way wrong.

The Right Way: Consistent Offset Direction and Dimensions

You want to keep your offsets the same across the board. So, if the offset was on this side, it needs to be on this side, this side, and then when you hit the end, you can bring it on the inside if you want. And you can have one of these at the other side offset on the inside if you want, but for the most part, these are on the same side of the grid line at a consistent offset.

We wouldn’t do like a 3-foot offset, 4-foot offset, 5-foot offset back to three. We want them for the most part on the same side of the grid line. And if they’re a 3-foot offset, we’re going to do three, three, three, three, three, and three. So that’s crucial.

Critical Mistake: Not Considering Building Components

But another thing is don’t just come in here and design your offsets or your grid lines on your slab on grade willy-nilly because let’s say that you have throughout the building a massive mechanical duct run that is running in this direction and you have some massive building components in your way and you have designed your grid lines to where when you bring them up the building you can’t plumb up through sleeves in the actual concrete decks and now you can’t really bring your horizontal control up vertically properly throughout the building.

The Three Key Rules When Setting Layout Points

Let me just draw the actual rules here. Number one, you will want to have consistency. Consistency in the direction of the offsets. You will want to have consistent offset dimensions. And number three, you will want to consider building components.

And when I say building components, what I mean is mechanical electrical plumbing that could be in your way, finished floors, like maybe you have exposed concrete floors, permanent structures. Is there going to be like gang boxes staged in your way? You want to design your grid system to where it’s as out of the way as possible and consistent.

Now, I’ll talk about this in the next video, so don’t get me talking too much. But if you have a high-rise, you want that secondary control grid on the ground floor to be where you at least have two points and you can plumb up through sleeves on each floor and that is the best way. Just want you to know there’s some debate about that. You can plumb up from the ground floor all the way up and control the plumb of that building. So these have to be done properly.

First Step: Ask the Craft What Offset They Want

Now let’s talk about working control specifically. Let’s say you have your grid lines and you want to go build a wall over here. The first thing that you’ll want to do is talk to the carpenters or the folks doing the work and you ask them what offset they want. Hopefully, it’s the same as the other so we don’t make mistakes. And they’ll say, “Okay, I want a 3-foot offset on this side.” Or maybe because they’re going to use tattletails, meaning they’re going to plumb from the top of the formwork, maybe they want a 6 inch or a 1 foot or, you know, whatever it is. Ask them what offset that they want.

How to Measure Parallel and Perpendicular Lines

When you do that, there’s a couple things that you can do here. Number one, if you’re setting this line and it’s at the right offset, you can measure from this line by holding here at this point and pulling a radius and holding at this point and pulling a radius. And then what you’ll do is you’ll snap past the farthest points to get a perfectly parallel line there. These are just a couple of the rules.

The other thing is sometimes we have to mark a perpendicular line and you can use the 3-4-5. Can you believe I was taught 6-8-10? I don’t know why that happened, but the base is 3-4-5. So, you can actually come down here and measure a multiple of 3-4-5 and measure three, make a mark. Measure four out here and do an arc. And then measure five and do an intersecting arc. And that means you can create a perpendicular line.

So, you’re going to use these two taping techniques to go from your grid lines over to your working control.

Two Benchmarks Per Building (Always)

But the bottom line is if I’m going to build this wall, I will want offsets that I can give to the craft and they might want a temporary benchmark over here. And I’m sorry, but if you are going to do a temporary benchmark and let’s say that on both sides of this building, you have two benchmarks. By the way, if this is a building, you want two benchmarks around that building.

Some people will say one because if it’s wrong, at least it’s all consistent. I don’t want it to be wrong. I want to be able to check into two benchmarks. There’s always two benchmarks per building.

So, if I’m going to set a temporary benchmark over here, I will set up my automatic level, backsight, foresight. Then I will backsight, foresight, backsight, foresight, close, and be able to get the new value for the elevation here. Anyway, so you are going to follow that commandment of every benchmark that you set, having gone through two other benchmarks, using three wire leveling, estimating to the nearest thousandth, and like I already said, closing back and adjusting the points if necessary.

Working Control Is Communication with the Craft

If you have working control for this wall, you’ll have your offset lines and you will have your benchmark working control and it’s temporary. So one of the things I like to do is if I’m doing these lines, I might spray down clear coat on the slab before I snap the line. Let it dry, then snap the line, then clear it again, so that one of these days when we’re polishing that floor, those marks will just come up and I won’t stain it if it’s exposed concrete.

But the bottom line is these should be temporary marks specific to the component. So, it could be for embeds, it could be for wall height, it could be a 4-foot offset line in the form, but working control needs to be a communication between you and the craft. Your grid lines need to enable it and how you’re going to take the rest of the building up through the structure.

Here’s the working control process:

• Consistent offset direction: Keep offsets on same side of grid line across the board. If offset on this side, needs to be on this side, this side. When hit the end, can bring on inside if want. Don’t do offset this direction, then that direction, then this direction. You’ll confuse somebody and get something way wrong.
• Consistent offset dimensions: If 3-foot offset, do three, three, three, three, three, three. Don’t do 3-foot offset, 4-foot, 5-foot, back to three. Keep dimensions consistent.
• Consider building components: Don’t design offsets or grid lines willy-nilly. Consider: massive mechanical duct runs, massive building components in way, whether can plumb up through sleeves in concrete decks, MEP in way, finished floors (exposed concrete), permanent structures, gang boxes staged in way. Design grid system as out of way as possible and consistent.
• Ask craft what offset they want: Talk to carpenters or folks doing work. Ask what offset they want. Hopefully same as other so don’t make mistakes. They’ll say “3-foot offset this side” or “6 inch or 1 foot for tattletails” (plumb from top of formwork). Communication between you and craft.
• Two benchmarks per building (always): Some people say one because if wrong at least all consistent. I don’t want it to be wrong. I want to be able to check into two benchmarks. Always two benchmarks per building. Set temporary benchmark: backsight, foresight, backsight, foresight, close. Go through two other benchmarks, three wire leveling, estimate to nearest thousandth, close and adjust points.

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A Challenge for Field Engineers

Here’s what I want you to do this week. Design your working control properly. Keep offsets on same side of grid line with consistent dimensions (three, three, three, three). Consider building components: MEP duct runs, can you plumb up through sleeves, gang boxes staged in way. Design grid system as out of way as possible.

Ask the craft what offset they want. Communicate. Set two benchmarks per building (always). Go through two other benchmarks, three wire leveling, estimate to nearest thousandth, close and adjust points.

Use two taping technique from grid lines to working control. Hold at this point and pull radius, hold at this point and pull radius, snap past farthest points for perfectly parallel line. Use 3-4-5 for perpendicular lines (measure three, make mark, measure four and arc, measure five and intersecting arc).

Working control is temporary marks specific to component: embeds, wall height, 4-foot offset line in form. Communication between you and craft. Your grid lines need to enable it and how you’re going to take rest of building up through structure.

As we say at Elevate, working control for field engineers: consistent offset direction and dimensions, consider building components, two benchmarks per building, communicate with craft.

On we go.

Frequently Asked Questions

What’s the difference between primary, secondary, and working control?

Primary control is precise, accurate, surrounds project site, permanent. Secondary control is building specific, semi-permanent (grid lines). Working control is component specific, temporary (wall offset lines, temporary benchmarks for specific wall or component).

Why keep offsets on same side of grid line?

Because if you do offset this direction, then that direction, then this direction, you’ll confuse somebody and get something way wrong. Keep offsets on same side across board with consistent dimensions (three, three, three).

Why consider building components when designing grid system?

Because if you have massive mechanical duct run and design grid lines without considering it, when you bring them up the building you can’t plumb up through sleeves in concrete decks. Can’t bring horizontal control up vertically properly throughout building.

Why two benchmarks per building instead of one?

Some people say one because if wrong at least all consistent. I don’t want it to be wrong. I want to be able to check into two benchmarks. Always two benchmarks per building.

How do you set a temporary benchmark?

Set up automatic level, backsight, foresight, backsight, foresight, close. Go through two other benchmarks. Use three wire leveling. Estimate to nearest thousandth. Close and adjust points if necessary. Follow benchmark commandments.