PS Exam Preparation

Comprehensive preparation for the NCEES Principles and Practice of Surveying (PS) exam. 5 modules covering all 5 exam domains with 50 in-depth topics.

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Lesson 11

As-Built/Record Drawing Surveys

Learning Objectives

After completing this topic, you should be able to:

Explain the purpose and scope of as-built surveys
Distinguish between as-built surveys and record drawings
Describe the field techniques used for as-built data collection
Identify what elements must be measured and documented in an as-built survey
Explain how as-built data is compared to design plans
Describe tolerance and acceptance criteria for constructed improvements
Understand the legal and contractual significance of as-built documentation

Overview

As-built surveys and record drawings document the actual position, elevation, and dimensions of constructed improvements after completion. While construction surveys (Topic 5.4) establish design positions before and during construction, as-built surveys verify what was actually built and how it compares to the design. This documentation serves as the permanent record of the constructed project and is essential for facility management, future design, regulatory compliance, and legal protection.

Key Concepts

Figure PS.5.11 — As-Built vs Design Comparison

As-Built Surveys vs. Record Drawings

These terms are related but distinct:

As-built survey:

A field survey performed after construction to measure and document the actual positions, elevations, and dimensions of constructed features
Performed by a surveyor using survey instruments
Produces measured data that can be compared to design plans
May be required at multiple stages of construction (foundation, underground utilities, finish grade)

Record drawings (as-built drawings):

Construction plans that have been updated to reflect actual constructed conditions
Typically prepared by the contractor or engineer by marking up the original design plans with field-measured deviations
May incorporate data from the surveyor's as-built survey
Become the permanent construction record for the owner and facility manager

Key distinction: An as-built survey is a measured survey product from a licensed surveyor. Record drawings are modified design plans that may incorporate survey data along with contractor field notes and inspector records.

Purpose of As-Built Documentation

Regulatory compliance:

Municipalities require as-built surveys to verify that construction matches approved plans
Floodplain administrators require elevation certificates to verify compliance with flood regulations
Utility departments require as-built surveys of underground utilities before backfilling

Contractual obligations:

Verify that the contractor built the project to specifications
Document deviations from the design for change order purposes
Establish the basis for final payment and project acceptance

Facility management:

Record the actual locations of buried utilities for future maintenance and repair
Document building positions relative to property lines for future development
Provide baseline data for future renovations and additions

Legal protection:

Protect the surveyor by documenting what was actually staked versus what was built
Protect the owner by documenting compliance with zoning, setbacks, and other requirements
Protect the contractor by documenting that work was performed to specification

Elements Typically Documented

Site improvements:

Building corners and foundation positions relative to property lines
Finished floor elevations
Finished grade elevations at key points
Parking areas, driveways, sidewalks, and curb locations
Retaining wall positions and top/bottom elevations
Stormwater management facilities (detention ponds, inlets, outlet structures)

Underground utilities:

Pipe invert elevations at manholes, inlets, and connections
Pipe sizes, materials, and slopes
Horizontal positions of pipes, conduits, and cables
Manhole rim elevations
Valve locations and depths
Service connection points

Building elements (when required):

Foundation dimensions and positions
Steel column locations
Floor slab elevations
Structural element positions for multi-story construction
Elevator shaft positions
Building height

Roadway and site grading:

Centerline alignment and profile
Edge of pavement positions and elevations
Curb and gutter positions
Ditch and swale inverts
Top and toe of embankment slopes

Field Techniques

Horizontal positioning:

Total station measurements from project control
GNSS (RTK) positioning for exterior features
Tape measurements for close-range details
Offsets from known reference lines

Vertical measurements:

Differential leveling for precise elevations (utility inverts, floor elevations)
Trigonometric leveling from total station for general features
GNSS-derived elevations for site features where appropriate
Rod readings into manholes and inlets for invert elevations

Timing considerations:

Underground utilities must be surveyed before backfilling (critical window)
Foundation surveys occur before framing (to verify position before vertical construction proceeds)
Final as-built occurs after all site improvements are complete
Some features can only be measured at specific construction stages

Common wrong path — as-built = as-staked. Two related but distinct deliverables: as-staked records document what the surveyor staked in the field (design position, cut/fill information, layout coordinates). As-built records document what the contractor actually built. The two are not the same thing, and both are important for different reasons. An as-staked record protects the surveyor — it shows that the correct design position was marked in the field. An as-built record documents deviations from the design for the owner, engineer, and future facility manager. Students on the exam sometimes conflate them, answering "the surveyor's as-built survey" when the question is really about the as-staked layout from construction stakeout (which is preconstruction documentation, not post-construction). The key distinction: as-staked happens before construction (shows design); as-built happens after (shows reality). If the question describes the surveyor's obligation to document what they staked, that's as-staked. If the question describes documenting what the contractor built, that's as-built. They're both valuable, but they're different documents with different purposes.

Quick retrieval check — try before reading on.

▶Your crew staked a new sewer line along a design alignment with invert elevation 120.50 ft at STA 10+00. Three weeks later, the contractor completed construction and requested a final survey before acceptance. You measure the sewer invert at 120.43 ft. Which deliverable documents this difference, and what should you do with the data?

The as-built survey documents this — the actual constructed invert is 120.43 ft, 0.07 ft below design. Compare to the as-built tolerance for gravity sewer invert (typically ±0.01–0.02 ft). The deviation of 0.07 ft exceeds typical tolerance, so flag it as a potential issue on the deviation report.

Report the data to the owner and engineer with the comparison against design, but do NOT decide whether the deviation is acceptable — that's the engineer's or owner's call, based on whether the 0.07 ft drop affects the gravity flow design or introduces a backflow risk. Separately, document that the as-staked layout was at design position (120.50 ft at STA 10+00) as shown in your original stakeout records — that separates "was it staked correctly" (yes, per as-staked) from "was it built correctly" (no, per as-built), allowing responsibility to be assigned clearly. The construction record should preserve both documents for the permanent project file.

Plan Comparison and Deviation Reporting

The core deliverable of an as-built survey is the comparison between design and actual construction:

Comparison methods:

Overlay as-built positions on the design plans
Compute horizontal and vertical deviations at each measured point
Prepare a deviation report listing all points that exceed tolerances
Color-code or symbol-code the drawing to highlight areas of concern

Typical deviation reporting format:

Feature	Design Position	As-Built Position	Deviation	Tolerance	Status
Bldg NE Corner	N 1000.00, E 2000.00	N 1000.05, E 1999.97	0.06 ft	0.10 ft	Pass
MH-1 Rim	425.50	425.43	-0.07 ft	0.05 ft	Fail
Sewer Inv MH-1	420.25	420.28	+0.03 ft	0.02 ft	Fail

Acceptance Criteria and Tolerances

Tolerances for as-built surveys depend on the project specifications and the type of improvement:

Improvement	Typical Horizontal Tolerance	Typical Vertical Tolerance
Building position	0.10 ft	0.02 ft (floor elev)
Road centerline	0.05 ft	0.02 ft
Gravity sewer invert	0.10 ft	0.01-0.02 ft
Storm drain invert	0.10 ft	0.02-0.05 ft
Water main	0.10 ft	0.10 ft
Finish grade	0.20 ft	0.05-0.10 ft
Curb and gutter	0.05 ft	0.02 ft

When tolerances are exceeded:

The surveyor documents the deviation
The engineer or owner decides whether the deviation is acceptable
Remedial action (reconstruction, redesign, or acceptance with conditions) is determined by the project team
The surveyor does not make the acceptance decision -- the surveyor provides the data

Elevation Certificates

A specialized form of as-built survey for flood zone compliance:

Required for buildings in FEMA-designated Special Flood Hazard Areas
Documents the lowest floor elevation, machinery/equipment elevations, and flood openings
Compared to the Base Flood Elevation (BFE) shown on the Flood Insurance Rate Map (FIRM)
Must be prepared by a licensed surveyor or engineer
Used for flood insurance rating and regulatory compliance
Required both pre-construction (foundation) and post-construction (finished)

Documentation Standards

As-built survey deliverables typically include:

As-built survey drawing showing all measured positions and elevations
Deviation report comparing as-built to design
Surveyor's certification of accuracy
Control information and datum references
Date of survey and equipment used
Digital data files (CAD, GIS) when specified

Record drawing standards:

Must clearly indicate which information is as-built versus as-designed
All revisions must be dated and initialed
Underground utility depths and materials must be clearly labeled
Final record drawings are typically delivered in both hard copy and digital format

Exam Tips

Underground utilities must be surveyed before backfilling -- this is the most time-critical as-built survey element
As-built surveys are measured data from a licensed surveyor; record drawings are modified design plans that may incorporate survey data
Gravity sewer inverts require the tightest vertical tolerances because flow depends on precise grade
The surveyor documents deviations but does not decide whether they are acceptable -- that decision belongs to the engineer or owner
Elevation certificates are a specific type of as-built survey required for flood zone compliance
Know the difference between an as-built survey performed during construction versus a final as-built at project completion
As-built data becomes the permanent record for facility management -- errors in as-built documentation can cause problems decades later when utilities are located for future work
As-staked records (from construction staking, Topic 5.4) protect the surveyor by showing what was staked; as-built surveys show what was actually constructed

PS Exam Preparation

Module 1: Legal Principles

Module 2: Professional Survey Practices

Module 3: Standards & Specifications

Module 4: Business Practices

Module 5: Areas of Practice