Concrete is a structural element which requires a great deal of thought and care for construction. Concrete is a great way to create structures for buildings, but due to the nature of the product, ensuring accurate placement, dimensions, mix-design, and location is essential to following through with a successful project. For instance, a small error in concrete placement location, or a miss on concrete reinforcement, can result in the necessity for chipping and replacement of concrete.
Getting concrete construction right the first time means understanding and reviewing the requirements/details of structural drawings. This, in addition, to reviewing the details of other disciplines, such as architectural and mechanical, overall bring together a project to ensure it is structurally sound, and built to facilitate the ongoing processes of other trades.
Table of Contents
- Top of Pile Elevation
- Grade Beam Schedule
- Pile Cap Schedule
- Rebar Shop Drawings
- Top of Slab Elevation
- Baseplate Layout
- Floor Types
- Concrete Column Schedules
- Monolithic Concrete
- Typical Structural Notes
- General / Typical Structural Details
- Structural Section Cut
- Project Gridlines
- Foundation Plans
- Slab Elevation Plans
- Slab Openings
- Misc. Connection Details
- Summary
Top of of Pile Elevation
A top of pile elevation is used in commercial concrete projects where piling designs are used to facilitate the support of the building structure. Top of pile elevation is critical to get right! It ensures that elements like pile caps are stationed correctly where they should be placed on top of the pile.
Top of pile elevation corresponds with building piling layout plans, where both the top of pile elevation and the corresponding pile number is provided. This information can be referenced with pile schedules for a project. Also, due to the nature of piles, generally the actual engineering of the details of piles of provided as a responsibility of a piling contractor.
This piling contractor takes precedence in ensuring not only reinforcement and placement of concrete are done properly, but also can make a major impact on the means and methods of earthworks for the piles to be installed safely and properly.
Variations in pile elevation typically coincide with variation in structure elevations, such as slabs, stairwells, elevator pits etc.
Grade Beam Schedule
A grade beam schedule provides a list of grade beams(concrete) for depth, width, and height that get utilized in concrete construction.
Generally a project will use a concrete grade beam schedule to identify the various grade beams and placements of such throughout various concrete structural foundation plans. Throughout the building foundation plans grade beam top elevation may be indicated, or it may be provided as a typical elevation through typical notes in the drawings. This same grade beam schedule is often utilized as reference in the shop drawings for rebar and structural reinforcement, turned over to the engineer for review.
Typically elevations of specific structural concrete elements are provided as typical U.N.O. (unless noted otherwise). This means a majority of foundational concrete elements are have the same top/cap elevation, but below grade excavation corresponds with the depth of the element.
Pile Cap Schedule
As concrete pile caps vary in sizes and dimensions, then the corresponding sizes, dimensions, heights, and widths will be identified with most projects in the structural drawings as the a pile cap schedule.
The pile cap schedule may also provide reinforcement details for utilization of the rebar detailers on the project. Pile caps are critical concrete elements, so the utilization of a concrete pile cap schedule, referenced with overall foundation plans, provides for the instruction required to ensure the right structural support is placed in the right locations(exactly).
Again, typical top of pile elevation is provided in typical structural notes, but can be noted otherwise in plans or specific drawing details.
Rebar Shop Drawings
With all concrete projects of major size, most consultants and structural engineers, in addition to some architects will require the use reinforcement shop drawings.
Reinforcement shop drawings are submitted as schematics and detailed bar lists for use by a rebar supplier to ensure that the products they order and supply to the job site actually meet the project specifics. If the details of the rebar shop drawings do not meet the specifications of the structural prints, at the time of pour, or placement of rebar, serious issues can arise with delaying the pour dates for instance.
Shop drawings for concrete reinforcement also are indicative of the skill of a detailer. A good detailer will generally interpret the structural prints well, but in some cases, poor detailing is done, or with omissions and conflicts through the typical details of a structural print, misses can occur. As such, multiple revisions of rebar shop drawing review are common.
Due to the scheduling of larger projects, reinforcement shop drawings are provided in phases, coinciding with various structures of the project, and naturally with identifiable pour breaks, or limits in the amount of concrete that can feasibly be poured.
The determination of pour breaks can be a joint effort between structural dictations and the means/methods of a concrete contractor. Reinforcement detailing can be coordinated accordingly.
T.O.S (Top of Slab Elevation)
Typically one of the most important features of concrete structural prints, the top of slab elevation or the main floor elevation indicates the main floor level typically of a concrete building. This is known to correspond with a geodetic elevation, which can then be used to correspond to various concrete elements which also critically need to be assessed for their elevation from the main slab height.
Such elements include pilasters, pile caps, piles, grade beams, and other slabs. In general, the positions of the main floor slab elevation are also critical for subsequent surveying practices for the rest of the building. Small errors in the placement of concrete foundations such as slabs or general outline from foundation walls or grade beams can be problematic in determining the final layout of a building in general.
Minor problems can leads to bigger intolerances in suites, or rooms throughout a building for instance. Top of slab elevation is the guide for general placement of formwork, in addition to any necessary architectural slab details.
In general, for concrete slabs, rebar details will be provided(printed) in addition to thicknesses on the drawing set itself(of MF slab and other slabs). This includes nomenclature including either slab type, concrete thickness, and even reinforcement details: for example a slab with 300mm O/C E/W T&B 15m rebar could be indicated typically throughout slab plans.
BP (Baseplate Layout)
A concrete baseplate layout is provided in the structural prints to allow for the placement of anchor bolts, and coordination with pile caps. A base plate layout also needs to be used in conjunction with the concrete pile cap cage shop drawings for instance to ensure the correct placement of the anchor bolts.
Concrete base plate layouts are critical not only in ensuring the correct construction of pile caps, but ensuring that the adjoining steel structural members actually align with the structural print’s intentions. The base plate layout as such, in addition to base plate details, once reviewed with the concrete pilaster schedule for instance, is also generally reviewed by structural steel trades. Small errors in baseplate installation/concrete-anchor bolts & embeds can cause inconveniences for subsequent installation of steel columns or braces etc.
Floor Types
Typically concrete slabs and concrete structures that are on grade or even suspended are provided a floor typed condition within the structural prints. Floor types may be provided details such as the granular sub-base requirements, geotextile, the concrete slab thickness, and any other considerations for proper construction of the concrete elements.
Concrete slabs, that are suspended, from an architectural perspective, will not indicate much detail, but the structural prints may indicate more detail. For example, suspended concrete slab construction is reminiscent of just the slab, unless a metal deck is used, so the architectural floor type may not be very interesting to look at.
However for the main floor level and slab on grade construction the slab will be provided the underlying construction means and methods in coordination with the project specifications to provide for a structural; sound project. In addition the concrete elements in more complex construction, such as with concrete toppers or other may include for other concrete elements, such as OWWJ(open-web wood joist), OWSJ(open-web steel joist), I-joist, etc. to indicate the total construction of the structural elements and items for the floor type.
Photo Above: A slab construction on-grade will typically need be coordinated with the earthworks (trade/discipline) for proper thicknesses of sub-grade fill and other sub-concrete products such as vapor barriers or high density insulation.
Concrete Column Schedules
Just like the concrete for pile caps and grade beams, the utilization of concrete schedules for concrete columns is a way that structural engineers and architects coordinate the structural requirements required for concrete structures in general.
For instance, a concrete column will be provided dimensions on the width and length of the item. Without the consultation of the column schedule, it can be sometimes difficult for concrete contractors to properly construct the elements provided by the intention of the structural prints. So reference to the structural drawing schedule, such as the column schedule to ensure the concrete column is constructed properly.
This can also help to ensure that the necessary steel reinforcement is left up from the slab or other elements like pilasters, ensuring connection of concrete structural elements through rebar.
Concrete Column Rebar Cage: Rebar detailing companies and installation companies generally aim to increase the effectiveness of installation. Utilization of concrete columns schedules along with corresponding rebar/reinforcement requirements allows for pre-fabrication of cages such as the following to be inserted into formwork for each column specific to the column. Concrete column schedules facilitate organization of both concrete and steel reinforcement requirements in this manner.
Monolithic Concrete
If specified and determined required by the services of a structural engineer the pour of certain concrete elements may need to be done monolithically. This means that no pour breaks are allowed in the pouring of the items.
Where instructed, the concrete contractor should try to construct and pour the concrete element in one go.
Typical Notes
Typical notes for a structural drawing set are essential in determining common characteristics that can be applied to a variety of structural elements, details, and scenarios for a concrete construction project. The typical details or general notes for the structural drawings of a project are some of the most important general notes to review to ensure not only compliance with the intentions of the structural engineer, but to fully understand the specific details for concrete elements.
It can be common to find some discrepancies between typical notes and specific/general details or section cuts. Where in question, then the more specific of the instructions should be followed, but it never hurts to double check with an engineer or achitect!
General / Typical Structural Details
General details or typical details are provided as specific scenarios and general details prevalent as conditions throughout a concrete structure or a project.
The use of general details and conditions on a project, indicated throughout the plans as section cuts, or call outs on the overall plans of structural prints allows for a concrete contractor to better interpret the requirement of the structural/architectural disciplines. These details can also be useful in determining the overall design intent of a specific detailed section of building prior to pouring, and for finalizing concrete formwork and reinforcement details.
Specific scenarios may also be included in general details, albeit, just called out less throughout overall structural floor plans.
Section Cut
A section cut on a structural drawing set, especially one for concrete construction, is provided to allow for the details of a specific section of slab, beam, transfer slab, driveway, or other concrete element to be noted and reviewed for it’s relation to surrounding elements.
These section cuts can also help to showcase the requirements for the utilization of rebar throughout the project, and therefor aid the rebar detailer in producing adequate shop drawings for the project.
Gridlines
The gridlines of a project are provided for structural and architectural drawings, in addition to mechanical and electrical drawings to showcase the various dimensional locations of various structural items throughout a project. The grid lines are used for coordination purposes with other trades, other disciplines and generally to ensure that the placement of concrete elements are located as per the design intent of the structural engineer of record. Gridlines are fundamental for the general coordination of construction projects.
Photo Above: Concrete foundations and footings are critical elements for alignment with project gridlines, setting the basis for the remaining concrete structure to be placed/poured.
Foundation Plans
On larger construction projects, it is likely that sub-grade conditions, such as plumbing or electrical may be present underneath the main floor slab elevation for other slabs throughout a building. Foundation plans for concrete construction outline the locations of grade beams, foundation walls, pile caps, piles and so on! Not only that, foundation plans can be used to coordinate with the mechanical and architectural disciplines to ensure that key stages of the construction process are not overlooked. This includes making all necessary plumbing and electrical trenching throughout the building footprint, with backfill, to make for the necessary placement of subsequent concrete elements like slabs.
Slab Elevation Plans (Architectural)
Typically elevation plans indicate side(west/east/south/north) views of architectural portions or structural buildings. However with some more detailed projects, the utilization of color coated or symbol coated elevation plans with architectural or sometimes structural plans can be critical in identifying depressed portions of slab, raised portions of slab, sloped portions of slab and so-on and so-forth. Concrete slab elevation plans provide various measurements from the main floor slab elevation to coincide with corresponding tolerances to vary from that main floor elevation.
Such modifications to the slab elevation, rather than a uniform main floor level, include patio slabs, entrances for doors, canopies, and more!
For example, one common slight depression in a slab, might be a pedestrian entrance grille product, coordinated between architectural and structural disciplines.
Photo Above: Main floor slab elevation is often the principal elevation to which other concrete elements(slabs) are provided locations(elevation change) from, with color coding or symbolic representation to indicate elevation changes and ‘steps’ in the slab.
Slab Openings
Throughout many structural plans, identification of slab openings are provided to indicate where buck-outs should be utilized to act as pass-throughs for various mechanical or electrical requirements. Such requirements include mechanical shafts, electrical shafts, ducts, and other vertical service spaces. Ensuring coordination of these slab openings with the general requirements of electrical, mechanical and architectural disciplines is important to avoid costly rework in the future.
Buck-outs are concrete form-work strategies utilized to facilitate the installation of openings in slabs. From a structural reinforcement detail perspective, expect to see a typical slab opening detail provided, inclusive of additional rebar to reinforce the opening… go figure!
Photo Above: A duct permitted passage through a concrete slab. This duct would need be coordinated for opening size through the concrete slab, between HVAC(heating, ventilation, air-conditioning trade) and the concrete contractor.
Connection Details
The interconnection of concrete and steel structures necessitates that trade discplines be coordinated. This means, concrete trades may be responsible, in working with a steel contractor, to provide embeds such as plates, lips, anchor bolts and more to facilitate the connection of steel members to concrete elements.
Connection details, typically are supplied by the coordinating structural engineer on a project as the connection between two separate disciplines, such as concrete with steel, can’t really be borne by either trade solely. The structural engineer on the project can ensure that not only will the concrete element be sufficiently strong enough to support the load of the steel member, but provide the suggested connection detail to faciliate the steel contractor to actually attach the member.
These sorts of details sometimes need to be coordinated between steel shop drawings and concrete plans. If missed, connection details can impose complications in the construction of concrete and steel buildings. Potential remedies include post-pour drilled anchors, but ideally, all the requirements for steel securement are sorted prior to the placement of concrete, with necessary connection components supplied in advance of the pour date.
Photo Above: Steel beam and steel deck connections to a concrete column. Note the yellow and blue paint, indicative of post-pour scanning to identify the locations reinforcement in the concrete column. Scanning of concrete permits the correct placement of post-pour anchor bolts for steel members, without damaging the structural integrity of the column, as the reinforcement within is kept intact.
Photo Above: Steel concrete anchor bolts from a roof concrete cap(concrete covered in roofing material). Although not of a primary structural frame steel nature, minor items like roof anchor tie off points and elements like ladders or stairs may also require structural embeds and connection details.
Summary
There are so many key concrete terms in structural concrete drawing review, and we have only covered some of the most important ones. Ultimately, as review into the structural plans of a building continues through various phases, more and more detail is revealed.
Understanding the typical use-cases of concrete terms is the goal, in general plan review, as an experienced concrete contractor will be able to properly review the set. Other key documentation that should be reviewed in conjunction with general structural drawings are the project specifications. Project specifications outline more specific detailed requirements pertaining to concrete placement, reinforcement and other means and methods of construction.
As time goes on, more and more definitions and terms will be added to this post, so stay tuned.
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