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Back to Basics: Fieldwork tips.

September 1, 2009
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Is there a way to make measuring in the field easier and more accurate? Yes, numerous strategies are used by surveyors to simplify their fieldwork. This column describes a few successful procedures that I have used personally or have heard of others using.



Is there a way to make measuring in the field easier and more accurate?

Yes, numerous strategies are used by surveyors to simplify their fieldwork. This column describes a few successful procedures that I have used personally or have heard of others using.

Figure 1. A 40d spike drives easily into hard ground and fits through a stake chaser.

Color Coding

Develop a color-coded system for your company or for the jobsite, and apply the code to each stake and lath that is set. This system makes it easy to identify points and helps the trades see at a glance which points apply to them.

Consider using a single color for actual building points. For offset points, add an additional color such as white or yellow. This way, it will be easy for you or anyone on the site to readily distinguish the actual layout points and their offsets.

Figure 2. Tie the ends of two chalk lines together and alternate lines with each snap.

Always color code control-line offsets, and try to keep them the same color in each area on the jobsite. For example, blue ribbons on lath might equal fill, red ribbons might represent cut, green ribbons might represent grade, and white ribbons might represent control points or structure points. Keep the system simple and consistent.

Using different-colored chalk lines is also helpful on a construction site. Each craft will be snapping lines for different layout references. It is wise to identify a specific chalk color for the surveyors and make sure no one else on the jobsite uses that color.

Figure 3. Lay out similar structures the same way as much as possible to promote consistency.

Staking

If the layout is in a small area, look at the plans and count how many points and offsets there will be. Scatter that many hubs and lath (plus a few extra) around the area. This way, you won’t have to pack the stake bag along with everything else.

Along a road job, drive and drop hubs at the required intervals. In hard ground, use a 40d spike rather than a wooden hub. The 40d spike drives easily into the ground and fits through a stake chaser (see Figure 1).

Always remember to position offset lath with the writing facing whatever is being offset. Otherwise, the structure may be built completely opposite from where it should be. (Yes, that has happened.)

On cut-and-fill dirt work, consider taking a few extra minutes to mark a line on the lath that designates an even foot-number cut or fill. This line can help eliminate mistakes on the jobsite.

Figure 4. When shooting elevations on elevated decks, place your laser or leveling instrument on a bracket attached to a structural column or shear wall to avoid vibrations affecting the level.

Layout

When laying out saw-cut joints on concrete paving while it is green, tie the ends of two chalk lines together. Have one person reel out line from one side and snap the line. Have the other person reel out line from the other side and snap the line, and so on. In this way, you will always have a fresh chalk line (see Figure 2).

Always check to a second backsight point prior to beginning layout. What if you are supposed to be occupying point No. 1 and backsighting point No. 2, but instead you occupy point No. 2 and backsight point No. 1? Your backsight distance may check flat, but your orientation will be wrong. Always check to a third point!

After you lay out a building and check your diagonals, you should occupy one of the building corners, take a backsight onto another corner of the building, and then turn an angle and shoot a distance to a property corner or control point. You can then compare the measured distance to a calculated distance between the same points. This is a good check because there are many instances of a house being laid out on the wrong lot.

Be consistent in your layout. This means you should lay out similar structures the same way as much as possible. Being consistent with your offset distances and the relationship of your hubs to the structures allows everyone involved to be aware of what the layout should look like (see Figure 3).

When you pick up where you left off from the previous day’s work, it is a good practice to check into one of the last hubs or lath you put in the day before to make sure everything is correct. This procedure is especially important if you have to jump different crews into a site. Although switching crews around should be avoided, sometimes it can’t be helped.

To save time when setting up primary and secondary control, select an existing backsight at least three to four times your farthest distance. Always pick a high spot such as a cell tower, water tower or tall building. Make sure you can see it from all of your primary control points and, if possible, from all of your secondary control points.

Figure 5. Consider using an umbrella stuck in a PVC pipe embedded in a 5-gallon bucket of concrete to shade your instrument.

Elevations

When shooting elevations on elevated decks, you should fabricate a bracket that can be attached to a structural column or shear wall. Place your laser or leveling instrument on the bracket to avoid vibrations affecting the level (see Figure 4).

When making repetitive level shots of the same elevation, a foolproof method to set grade is to use a 2-by-2 board as a dummy rod to mark your backsight and calculate the difference between your bench mark and the grade shot you will be taking. Next, measure up or down as needed on the dummy rod, and mark your foresight. Then all you have to do is sight on the mark on the rod and set the elevation on the grade stake. This procedure removes the possibility of reading the wrong number and creating an error, and it also speeds the measurement process.

Always set up the instrument with its level bubble in the shade. The radiant heat of the sun can heat one side of the bubble/instrument and cause movement. If shade is not available, consider using an umbrella stuck in a PVC pipe embedded in a 5-gallon bucket of concrete (see Figure 5).

When setting anchor bolts in piers, use a template that can be adjusted up and down to ensure the correct projection of the bolt. The concrete needs to be placed to a certain elevation, usually based on the plans. The template is then adjusted up and down so that when it is placed in the pier, there is enough projection of the bolt to allow the leveling nut to be set at the correct elevation and enable the specified amount of grout to go under the column. Put tape around the bolt to prevent the nut from moving vertically and to protect the threads during the pour.

These are just a few of the thousands of fieldwork shortcuts that are used daily on the jobsite. In today’s world of button-pushing layout, many of these procedures are forgotten skills. However, they’re definitely worth a second look.


Web Exclusive! If you have timesaving measurement tips to share, view this column at www.pobonline.com and enter them under “Comments.”  Click Here to link to Crawford’s Construction Surveying and Layout group on Facebook.

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