Surveying On Site

There are many different elevations at each level, or slab. These varying elevations allow for different finishes/uses on top of that floor. For example, pavers, planters and tiles in the bathrooms require more “room” to put drains beneath them. This need for space translates into a depression in the slab. Simply put, there are ups and downs throughout the surface of the slab making it uneven.

The construction challenge that exists here is determining exactly where the slab rises or falls or determining exactly where “things” go. By this, we mean taking the drawings from the architect-engineer and in real life, on site, establishing exactly where building lines, drain locations, anchor bolts, walls and other items actually go.

Without the right knowledge and tools, it is an incredibly difficult task to figure out if you’re making the dimensions of the building according to the plans. Determining the dimensions and spacing of items is crucial to the success of the project. This is where surveying comes into play.



At the Kravis Center, surveyors utilize an electronic/optical instrument known as a total station. The total station enables the surveyor to quickly and efficiently determine the location for specific items on the jobsite. A surveyor uses to total station to “shoot” the location of the item, and the total station computes the distance and angle using radar.

In order to accurately determine the location, the surveyor needs to update inputs for factors such as temperature or moisture at the site. Weather conditions can affect the speed of the radar, which is used to calculate the distance. Once the distance is found, the total station quickly computes dimensions with trigonometry. Although the total station does the laborious computations, the surveyor must still understand and be able to check the math to ensure the computer is providing accurate data.



Unlike older equipment, the total station allows the surveyor to shoot 360 degrees around the control point (known location). As long as there is a line of sight, the surveyor can use the total station to determine dimensions.

All the data points are set on coordinates. Just like the algebra you tried to forget from high school, each point has an x, y and z component. The surveyor takes this data to locate the items in relation to the formwork. The total station also plays a role in BIM coordination, which is used by almost every trade to plan the construction process. With the points shot by the surveyor, the total station can create a 3D computer image of the space on site. This improves coordination and success on the jobsite.

How do buildings grow?

Have you ever wondered how each level of a building is added to the one beneath it? The important question to ask is how each floor supports the one on top of it.

The answer is a shoring. The simple use of the word shoring in construction describes a process of supporting a structure in order to prevent collapse so construction can proceed. In this case, shoring refers to column-like metal posts that are used for support. You are most likely familiar with scaffolding, which is often seen on the outside of buildings during construction; it allows workers temporary access to higher levels. Shoring is similar to scaffolding because it is a temporary addition to the jobsite to enable the completion of work.

The purpose of this shoring is to support concrete decks at each level until they have reached maximum strength. Otherwise, each floor would be added to a floor unable to carry the weight of the load and would cause a collapse.

Below is a photo of the shoring system being installed at the Kravis Center. The ground is the slab on grade we learned about last week, and the shoring it built up to prepare for the first level deck.

The photo below is a view from on top of the shoring completed for level one. The corner of each deck panel corresponds to a piece of shoring beneath it. String is laid, like in the photo, to represent where future mechanical work will be. It is important to make this indication so inserts (similar to mechanical fasteners and also shown in the photo) can be strategically placed for the purpose of supporting mechanical piping.

The deck also varies in height. In the photo below you will notice the different depressions. In the future, a concrete beam will be in the place of the lowest depression in the middle of the photo. Rebar will be added and all concrete will be poured on the deck at the same time.

There are also special procedures to create support around columns that are going through the deck. These procedures are important, because without them, the deck could essentially fall around the column, as though the column is punching a hole through the deck. To prevent this, stud rails are secured from the rebar in the concrete in the depression, up to the rebar in concrete slab.

Once level one deck has reached at least 75% of desired strength (no sooner than seven days), a process of reshoring begins. This process includes removing select shoring (the post-like supports) and moving them to the next level to provide the same support for the weight of the additional levels to be added. The shoring left at the bottom floor is spaced to still effectively support the structure. This process of shoring and reshoring will continue as each level is added. The reshoring will not be removed until the last deck (at the Kravis Center, the fourth deck) is poured and has reached strength.

Concrete in the basement

The basement floor has concrete! Everyday the Kravis Center looks closer to what we’re used to seeing in a parking garage. In this blog, we’re going to learn about the work that goes into that concrete on the ground, known as “slab on grade” or S.O.G.

Once the underground electrical and plumbing work was completed, the sub-grade was prepped with 2” of sand and a 15 millimeters vapor barrier. This Stego Wrap is covered by another 2” of sand. In order to have electricity to the building, some electrical conduit is run from underground, through the sand, vapor barrier and concrete.

Once the sub-grade is done, rebar is laid. There is one layer of rebar which is designed in a cross pattern about 18” apart. The slab also has fiber mesh, which are strands of plastic mixed in the concrete at the batch plant. The rebar serves to strengthen the concrete, as we’ve mentioned in the blog before. The fiber mesh helps prevent cracking. The slab poured in our basement is 5” thick.

The first pour was 15,000 square feet (s.f.) and 330 cubic yards (c.y.); the second pour was 20,000 s.f. and 420 c.y. of concrete. The videos below show concrete being poured. You’ll see there is a self-propelled laser screed machine being used in the video. This is necessary to vibrate the concrete in order to ensure the concrete consolidates around the rebar. The screed also levels the concrete (you will see is moving across the surface of the poured concrete).

Finally, the slab was finished with a swirl pattern in order to provide traction to vehicles. Otherwise, if this weren’t done, it would become slippery when wet.

As you walk through a building, have you ever thought of exactly what you’re walking on? Have you ever given a thought to what’s beneath the carpet and concrete?

In the dirt lies plumbing and electrical work that is coordinated months in advance of digging trenches. BIM (Building Information Modeling) is the latest technology utilized to accomplish coordination among subcontractors. After all, there is only so much space for the plumber and electrician to lay their pipes or conduits. It takes time and careful planning to ensure all parties can put their materials in while meeting the quality specifications of the building.

This image, above, is a snapshot of the underground work, generated by NavisWorks (BIM software). We’re looking at it from below ground, up toward the dirt that covers it. The yellow indicates electrical conduit running into the main electrical room. The green and pink are plumbing pipes running underground.

The photo below shows 7 electrical conduits placed in a trench, running away from the main electrical room. This number of conduits in one trench is slightly higher at than average, due to the size of the project. It will take the electrician 20 days to complete all underground work. It’s surprising to see progress made so quickly every day. Trenches are dug, conduit placed and then trenches need to be back filled (put dirt or another mixture over them).

At this project, the rocky nature of the soil requires the use of a concrete-like mixture to take the place of dirt, as you can see in the photo below. A red caution tape is also placed on top to tell someone in the future to be cautious, since there are critical lines running beneath the mixture.

The Main Electrical Room houses switch gear, main panel boards, lighting control panels and transformers. As you can assume, these control and monitor the electrical elements of the building. Here is another image from NavisWorks, showing the various items (the yellow boxes) inside the electrical room. As you can see, there is a lot of equipment to fit into one room.

The Electrical Room also requires special conditions. For example, during operation, the room must be consistently kept at a moderate temperature level. The walls of the room must also be fire rated for one hour, per code. However, as mentioned in our previous blog, an advantage of using concrete is the slow spread of fire, so the walls around the Kravis Center’s Electrical Room are rated above an hour.

Is that concrete coming out of a hose?

Shotcrete is concrete that is applied with a pressure hose, which may contradict your perception that concrete is something that is always “poured” into place. It is projected at a very high velocity onto a surface. At the Kravis Center, we’ve been using shotcrete for basement walls. In the pressure hose, the concrete is placed and compacted at the same time, which is especially helpful for spraying onto vertical areas. To date we have placed approximately 10,000 Cubic Yards of concrete utilizing the shotcrete method.

Interestingly, a taxidermist, not an engineer nor construction worker, invented shotcrete in the early 1900s. The taxidermist would blow dry material out of a hose with compressed air, wetting it as it was released. The method was quickly applied to construction and was first use to “patch up” weak buildings. In 1911 a patent was made for a “cement gun.”

When working with concrete, builders chose from a concrete pump or a shotcrete pump. Shotcrete is utilized for larger jobs that demand more durability and long distances. Additionally, concrete pumps use thinner mixes than shotcrete pumps.

Seem familiar? Shotcrete is frequently used for swimming pools, so you might have seen this performed in your backyard. Shotcrete is also used for dams, tunnels, retaining walls, shear walls and seismic reinforcing.

Whether you’ve seen it before or not, you’ll enjoy watching the shotcrete video of work going on at the jobsite. With the set-up used at Kravis Center for shotcrete, we are able to place approximately 1700 Cubic Yards of shotcrete per day. Once the shotcrete is allowed to setup it is finished with a rubber float or hard trowel depending on the finished look the architect requires. The walls shown in the video took 8 hours to place the 1,500 cubic yards.

Green Progress at CMC

Bernards is excited to make the Kravis Center the second LEED® certified building on Claremont McKenna College’s campus. CMC and our team are shooting for LEED® Gold on this project and are committed to finding real, sustainable building solutions to lessen the negative environmental impacts of construction. Bernards has 4 seasoned team members on-site that are LEED® Accredited Professionals, and 42 company-wide, that are well versed in sustainable building.

Claremont Residence Hall

LEED®, or Leadership in Energy and Environmental Design, is managed by the U.S. Green Building Council, and provides a set of standards for new construction and renovations to make construction greener. Increased momentum toward sustainable building has turned LEED® into a bit of a “buzzword,” so we want to dig a little deeper and tell you exactly what areas we’re working on to achieve LEED® Gold.

LEED® identifies six categories for builders to improve their construction process: sustainable sites, water efficiency, energy & atmosphere, materials & resources, indoor environmental quality, and innovative design. In our last blog, we touched on the “materials & resources” when we told you about the recycled content in our concrete and rebar.

At the Kravis Center, we’re doing a number of things to increase energy efficiency. With innovative designs, we will cut our energy usage 44% more than minimum LEED® requirements. Our Modular Active Chilled Beams (MAC Beams), which are responsible for cooling the building, plays a key element in reducing energy consumption. After all, typical heating and air conditioning is responsible for about 30% of total energy consumption in the United States, according to the Energy Information Administration (U.S. Government). Utilizing chilled beams will help reduce this number.

Active chilled beams have been used since the early 1990s and have been more prominent in Europe. Unlike traditional air conditioners that force air into the room at the desired temperature, chilled beams are more efficient and quieter because there are no moving parts in the rooms they are cooling. Simply put, warm air rises to the beams, which are similar in size and shape as a light fixture, air is chilled over the coil, so fresh, cool air is disbursed into the room.

Stay tuned as we share more green building innovations used at the Kravis Center.

Concrete is one of the most versatile, durable and cost-effective building materials known to man. It is also environmentally sustainable, with green credentials that outperform steel and timber. Concrete is used extensively throughout the Kravis Center, from our large concrete spread footings to the 24” thick, post tension floor slabs.

Concrete has excellent thermal mass energy consumption that can help reduce greenhouse gas emissions. This relates to how concrete absorbs and releases the heat from the sun. Because of its slow rate of heat transfer, a concrete building stays cooler during the day (meaning less air conditioning) and slowly emits the built up heat during the evening (meaning less heating costs). This slow rate of heat transfer, coupled by the fact concrete is completely non-combustible; it is an incredibly effective barrier to the spread of fire.

The first form of concrete was used by the Romans, but the method was lost for centuries, until its use was renewed by the British in the late eighteenth century. However, the modern mixture known today is only about 175 years old. The greatest improvement to the use of concrete is the application of rebar.

Reinforced concrete utilizes steel reinforcement bars, commonly referred to as “rebar.” Rebar provides the structure with more tensile strength (prevents bending and resists compression) and is included in most construction components, including slabs, walls, beams, columns and foundations.

The Kravis Center is striving to achieve a LEED® Gold Certification. LEED is a Green Building Rating System that judges the extent of a building’s environmental sustainability. As part of meeting our LEED goals, all of our concrete mixture and rebar comes from recycled materials. Our concrete is from 100% post-industrial recycled materials and our rebar is from 20% post-industrial and 80% post-consumer recycled materials. We also use locally harvested materials, reducing the distance work trucks must transport our materials for concrete.

In this photo above, concrete is being conveyed through a hydraulic Boom placement pump. Concrete is batched at a remote location (a few miles down the road from CMC), and we have about 90 minutes from batching to placement. In a future blog, we'll explore more about the various ways concrete is placed.

116' Above Claremont

This week, some of our Bernards team members climbed atop our 116 ft. tall tower crane. You can see our crane from all around the Claremont area, but do you know where these cranes started?

Adapted from shipyards, tower cranes became vital in the reconstruction of Germany after WWII. Business owner and inventor, Hans Liebherr, remodeled tower cranes in a way to make them more affordable and practical for use. Since the late 1940s, tower cranes have been the lifeblood of construction in Europe, Asia and the Middle East, because they're convenient for hoisting materials in tight, urban areas. Their popularity in the United States has drastically increased over the last decade, with Engineering News Record estimating they've tripled in use.

Tower cranes are used to lift steel, concrete, large tools and a wide variety of building materials. Although erecting and operating the crane can be costly, it's incredibly time effective.

The jib, this long "working arm" that extends horizontally, carries the load (items being lifted by the crane). A trolley runs along the jib to move the load in and out from the crane's center. On the opposite side, is a shorter "arm" that carries counterweights. Our crane, at the very end of the jib can carry 17,181 lbs!

The crane operator sits in a cab at the top of the tower, and in order to hook and unhook loads, the operator works with a signaler, or "rigger." They are constantly in radio contact and using hand signals. The rigger is responsible for the safety of the rigging and loads.

The size and structure of the tower crane can seem a little unnerving, after all, why doesn't it just fall over? The stability comes from a large concrete pad, which is poured before the crane is erected. On our site, the pad measures 24' by 24' by 3'-4". There are also blots that connect the tower structure to the pad. Safety is a top priority for us, and before our crane was used, it was inspected by a third party and Cal OSHA.

Our tower crane will be standing tall until about March 2010. You can take a look at how the crane was erected at the end of June 2009 in the video below.

Shear Walls & Columns

Rebar is standing tall and concrete is being poured. After digging in the dirt for weeks, we are finally coming out of the ground with Shear Walls and Columns. The soil in this area has a large amount of rocks. The ground is affectionately known as “potato” dirt. Unfortunately these little potatoes can be as large as 4’ in dia., which makes shoring piles interesting to say the least. Not to mention the spread footings end up being over excavated as the soil will not maintain a true edge. Although the foot print of the site is around 40,000 sf there is only one ramp access and with the large size of the footings and numerous columns, real estate in the hole is at a premium.

Shear wall boundary steel





Preparing for re-bar at spread footings



Working around column steel

Project History

The project was made possible from a donation by The Marie-Josée and Henry R. Kravis Foundation. In recognition of this gift, the College is designating this new signature building as "The Kravis Center."

We have a live webcam (link to your right) that captures the jobsite. Look how far we've come!

December 2008

April 2009



May 2009


July 2009