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How to Use Marking Flags on Construction Sites (Updated 2020)

How to Use Marking Flags on Construction Sites (Updated 2020)

No matter how rapidly technology evolves, there are still traditional ways of communication that continue to be effective up until today. Regardless of the invention of text messages and emails, the most straightforward way to convey information is to put up signs and markers.

With tangible markers, there’s no need to stop every passerby just to let them know about warnings or important messages. Markers also make warnings stand out and easily seen, even from a distance. 

Highly visible and eye-catching markers mean fast delivery of information. For this reason, one of the most commonly used markers in various industries at present is a marking flag.

What Are Marking Flags?

We’ve all seen flags at some point in our lives. Most of the time, they symbolize nations. In some cases, they represent religions and other organizations. They might even serve as a form of communication, like waving a white flag to concede defeat or a red flag to signal warnings. Whatever they are representing, they unfailingly catch the attention of everyone nearby. 

Marking Flags

Flags are typically rectangular pieces of fabric with unique designs and colors. They are attached to poles or staffs, and they are meant to stand upright or positioned diagonally. When it comes to marking, the flags used are not too different from the flags described above.

Solid Color Marking Flags

While marking flags do not represent organizations or countries, they are nonetheless essential in many industries. They are mostly rectangular, but some have a triangular shape. Like other flags, they are also fixed to poles.

What makes marking flags different from most flags is that they usually sport highly visible solid colors. Because they come in a variety of colors, these flags are useful for color-coding different objects.

In agriculture, marking flags can be used to identify freshly fertilized soil and to mark plots and crop rows. In landscaping, they can be placed in areas that need to be modified. In these industries and several others, marking flags allow professionals to get their job done more efficiently. This fact rings true for the construction industry as well. 

various sizes Marking Flags

In construction zones, marking flags of different colors are placed in several locations, and they represent underground utility lines. Each color symbolizes the type of underground utility that the flag is identifying.  Moreover, marking flags come in various sizes, but the most common ones are 2 by 3, 4 by 5, and 5 by 8 inches. In general, using these flags contributes to the overall safety of construction projects, from start to finish.

Importance of Marking Flags

In the U.S. alone, there are over 20 million miles of underground utilities. This means there are also many cases of people digging around without calling the national “Call Before You Dig” 811 phone number. Because of the absence of prior consultation, a lot of utility lines get accidentally hit and damaged. This doesn’t only mean extra repair costs, but it could also result in toxic substances leaking from pipes as well as other kinds of hazards. 

Damaged utility lines can disrupt projects, adversely affect surrounding businesses, and even jeopardize the safety of the community. As a matter of fact, there are some cases wherein damaged gas lines had led to explosions, which resulted in injuries and casualties.

That said, marking flags might not seem necessary at first glance, but in reality, they are extremely important in construction. Before people start to dig around the construction area, putting up marking flags can go a long way when it comes to safety. These flags can immediately warn excavator operators against digging into a certain location. They also let other professionals know the specific hazards to look out for in the area. Warning construction professionals about buried utility lines prevents costly damages and dangerous accidents. It is one of the first steps to ensure the safety of everyone involved in the project.

Since marking flags inform professionals about underground utilities, they help these professionals plan the layout of the construction area. With these flags, professionals will be able to know which locations to avoid and which areas are safe for digging. Marking flags thus improve both the safety and efficiency of construction projects. 

Kinds of Marking Flag Staffs

Before using marking flags, you must know the most common types of staffs they use. By being ready with this information, you can determine which kinds of marking flags are suitable for the project at hand. 

Outdoor conditions vary from one place to another. To suit various field conditions, manufacturers of marking flags use durable materials for the flags’ staffs. For better visibility, these staffs typically come in lengths of 18, 21, 30, and 36 inches.

1. Wire

Wire Flag

Because of their bend resistance, wire staffs can withstand difficult terrain and harsh field conditions. They are normally constructed with carbon alloy steel, which makes them durable and shock-resistant as well. Moreover, they have better tensile strength than other kinds of staffs. When the construction site demands heavy-duty flags, using marking flags with wire staffs is your best bet. 

Compared to other kinds of staffs, wire staffs can be simply thrust into the ground by hand. Some flags with plastic staffs call for the use of a specialized tool that can insert these flags into the ground. Aside from being durable, wire staffs reduce the time and cost spent on marking. 

2. Plastic

Plastic Flag

Marking flags with plastic staffs can provide you with additional safety in hazardous construction areas. Since most wire staffs are made of steel, they can conduct electricity when they come in contact with energized lines. Compared to wire staffs, plastic staffs provide better insulation against electricity. 

Plastic staffs are also safe to use around heavy equipment. In the event that they get sucked up by engines, they will not cause damage to machines the way wire staffs can. Aside from this, they are durable and resistant to corrosive elements.


3. Fiberglass

Fiberglass Flag

In extremely hot or cold weather, wire and plastic are not the best choices of marking flag staffs. There’s a high chance that drastic changes in temperature can affect the structure of these materials. In extreme temperature conditions, flags with fiberglass staffs are the most suitable marking flags to use. 

Because of their fire-resistant and weatherproof properties, fiberglass staffs can withstand any weather and temperature condition. They’re also long-lasting and extremely durable. Like plastic staffs, fiberglass staffs are excellent electrical insulators, so they’re entirely safe to use around energized lines. 

Requirements for Marking Flags

After determining the best flag staffs to use on the construction site, you must check if the marking flags follow the requirements of the American Public Works Association (APWA). This nonprofit organization advocates the exchange of knowledge among professionals in all aspects of public works. It has also set the standard color code and marking guidelines for underground utilities.

The purpose of marking flags is to let excavators, other construction professionals, and the community know about the presence of underground utilities. They should catch the attention of people nearby and have colors representing the types of utilities they are identifying. For this reason, APWA recommends that marking flags should be highly visible. Brightly-colored marking flags can be easily seen by people in low light conditions, under broad daylight, and from a distance. 

In addition to this, materials that make up the marking flags and their staffs should be durable. As was previously mentioned, marking flag staffs are usually made of wire, plastic, or fiberglass. These materials enable the staffs to endure harsh outdoor conditions. 

Apart from this, the marking flags’ fabric should also be long-lasting and wear-resistant. With this type of fabric, marking flags can retain their highly visible color in any field condition. 

Another APWA recommendation for marking flags is that they should indicate the name, initials, or logo of the excavator company. They should also display the width and other information about the utility line. This recommendation is applicable to marking flags with sufficient printing space. 

Abbreviations on Marking Flags

To fit the available space on marking flags, the APWA has made standardized abbreviations that construction companies can print on their flags. These abbreviations can represent facility identifiers, underground construction descriptions, and infrastructure materials. 

1. Facility Identifiers

  • CH for chemical
  • E for electric
  • FO for fiber optic
  • G for gas
  • LPG for liquefied petroleum gas
  • PP for petroleum products
  • RR for railroad signal
  • S for sewer
  • SD for storm drain
  • SS for storm sewer
  • SL for street lighting
  • STM for steam
  • SP for slurry system
  • TEL for telephone
  • TS for traffic signal
  • TV for television
  • W for water
  • W printed in purple for reclaimed water

2. Underground construction descriptions 

  • C for conduit
  • CDR for corridor
  • D for distribution facility
  • DB for direct buried
  • DE for dead end
  • JT for joint trench
  • HP for high pressure
  • HH for hand hole
  • MH for manhole
  • PB for pull box
  • R for radius
  • T for transmission facility
  • STR for structure, which includes vaults, junction boxes, inlets, and lift stations

3. Infrastructure materials

  • ABS for acrylonitrile butadiene styrene
  • ACP for asbestos cement pipe
  • CI for cast iron
  • CMC for cement mortar coated
  • CML for cement mortar lining
  • CPP for corrugated plastic pipe
  • CMP for corrugated metal pipe
  • CU for copper
  • CWD for creosote wood duct
  • HDPE for high-density polyethylene
  • MTD for multiple tile duct
  • PLA for plastic conduit or pipe
  • RCB for reinforced concrete box
  • RCP for reinforced concrete pipe
  • RF for reinforced fiberglass
  • SCCP for steel cylinder concrete pipe
  • STL for steel
  • VCP for vitrified clay pipe

Colors and Their Meanings

Colors and Their Meanings

For the sake of uniformity and clarity, the APWA encourages all companies involved in excavation to use the Uniform Color Code as stated under the ANSI Z535.1 standard. This way, anyone will know right away what type of utility line lies under the ground.

Red flags represent electric power lines, conduits, or lighting cables. They help prevent excavators from coming in contact with these energized lines, which can cause electrical shock hazards and loss of power in the area.

Yellow flags indicate pipes containing gaseous materials, such as gas, oil, steam, and petroleum. When these pipes get accidentally hit, it can lead to gas leaks or a possible explosion. 

Orange flags symbolize communication lines, alarm or signal lines, or fiber cables. These lines are responsible for the area’s access to the internet, telephones, and television.

Blue flags signify potable water, while purple flags stand for slurry, irrigation, or reclaimed water. There are also green flags that represent sewers and drainage facilities. If any of these utility lines get hit, they will likely flood the area, cause water damage, or even release toxic substances.

Besides identifying utility lines, some flag colors are used for marking other things. For instance, white marking flags are placed around the boundaries of the proposed excavation site. Other than this, surveyors use pink flags to make temporary survey markings as references for measurements. 

How to Use Marking Flags

Before placing marking flags, excavators need to know all of the locations of the buried utility lines as well as the full extent of these lines. They should consider the type of utility line being identified, the terrain in the area, and the kind of excavation that will be done. 

Inserting marking flags into the ground is easy. Using your hand, simply push the end of the staff into the ground, and that’s it. However, some types of marking flag staffs require an insertion tool to anchor the flags into the ground.

There are different ways of marking utility lines with flags. A single utility line, in particular, can be marked in two ways. Professionals can place their marking flag approximately over the center of the utility line. They can also put their flags at the ends of the utility lines. For conduits or ducts, marking flags can be placed on the outer extremities or edges of these utilities. 

When marking multiple utility lines of the same kind, professionals can place the marking flags over the center of these utility lines. Their flags should indicate the width and the number of these utilities. 

In some cases, multiple utility lines of the same kind are bundled in one trench or corridor. The number of lines is usually tricky to identify in this kind of utility arrangement. For this situation, professionals can place their marking flags approximately over the center of the utilities. These flags should also indicate the width of the trench in which the utilities are intertwined.

For proposed areas of excavation, white flags are used to delineate the boundaries. They can mark the four corners of the area, mark the center point of the area’s radius, or outline the borders of the excavation project.

Choosing the Right Marking Flags

Marking Flags

Since marking flags are used outdoors, they have to be designed for outdoor applications. What’s challenging in outdoor settings is that the weather and field conditions are pretty unpredictable. That’s why marking flags should be durable enough to withstand harsh elements and extended periods of standing upright outdoors. 

Not only should the staffs be made of heavy-duty materials, but the flags should also be securely attached to their staffs. A great way to ensure this is to check if the flags are wrapped around the staffs instead of merely glued. Strong winds and rain will not be able to separate the flags from their staffs with this kind of construction.

Another thing to consider when choosing marking flags is their level of visibility. Their staffs should be long enough to raise the flags at a visible height. The flags, on the other hand, should have colors that are bold enough to stand out in any light condition and from a long distance. 

Lastly, excavators and other construction professionals should always be prepared with a great number of marking flags. This way, they will be ready when faced with several utility lines that need to be marked. 

As an authorized distributor, Engineer Warehouse only selects products of the best brands to meet the specific needs of professionals. That’s why we offer marking flags of only the highest quality. These flags can surely endure the toughest field conditions. They come in different sizes and various highly visible, long-lasting colors. They also come with a variety of staffs to suit the needs of the job site. Moreover, they are sold per piece or per bundle of 100 pieces, so you can conveniently stock up for the next project.


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