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.