As-built records and handover

When construction ends, the building passes to people who were not there when it was built: the owner, the property manager, maintenance staff, future tenants and contractors who will renovate it decades later. They will rely on the records the construction team leaves behind. Record drawings show what was actually built and where; as-built surveys show the positions of key elements; scans and photos show what is hidden in walls, ceilings and slabs. Good records save money and prevent accidents for the whole life of the building. Poor records lead to exploratory demolition, cut services and drilled tendons. This lesson covers the kinds of as-built information, how field engineers build records during construction rather than at the end, the legal and contractual context, and the handover of records to the owner. CON-375 covers project documentation more broadly and CON-385 covers commissioning and closeout.

Kinds of as-built information

Terms vary between contracts and regions, and the differences matter.

A design team that prepares record drawings from contractor information usually states that it relies on that information and does not guarantee its accuracy. That is one reason the field engineer's records must be accurate: they are often the only source of the as-built truth.

Building records as the work proceeds

The most common failure in as-built records is leaving them to the end. Months after a sleeve was moved or a wall was shifted, nobody remembers exactly where it went. On Larkspur Commons, Thornbury builds records continuously.

• Every answered question and change is posted on the current set as it arrives (lesson 2), so the working drawings stay current.
• Trades mark deviations on a designated redline set each week, and the field engineer reviews the markups at the weekly coordination meeting.
• The layout log and the control sheet record what was laid out, from which control and drawing revision.
• Critical items are surveyed after installation: anchor bolts, embed plates, hold-down couplers, cladding anchors, pile positions and column positions.
• Underslab and in-slab services are photographed and surveyed before the pour; walls and ceilings are scanned or photographed before closing.
• Out-of-tolerance items are recorded with the design team's disposition, so the record shows what was accepted and why.

This continuous approach makes the final record set a matter of compiling and checking rather than reconstructing. It also means the records exist if something goes wrong during construction, when they are most needed.

As-built surveys of critical elements

Some elements are worth surveying individually because later work depends on their exact positions or because they will be hidden. A deviation report compares surveyed positions with design positions and flags any that exceed tolerance, so that each can be resolved and documented.

# As-built deviation report for record documents: surveyed points against design (mm, invented)
import math
points = [  # (id, category, design E, design N, built E, built N, tolerance)
    ("C-B2", "column", 7800, 7800, 7803, 7798, 12),
    ("C-C3", "column", 15600, 15600, 15608, 15606, 12),
    ("C-E7", "column", 46800, 31200, 46796, 31209, 12),
    ("EP-01", "embed plate", 0, 4200, 4, 4206, 10),
    ("EP-07", "embed plate", 23400, 39000, 23413, 39003, 10),
    ("SL-M12", "sleeve", 23850, 10300, 23860, 10301, 25),
    ("HD-14", "hold-down coupler", 31200, 11700, 31205, 11697, 6),
    ("HD-15", "hold-down coupler", 31200, 15600, 31209, 15601, 6),
]
out = []
for pid, cat, de, dn, be, bn, tol in points:
    d = math.hypot(be - de, bn - dn)
    flag = "" if d <= tol else "  <- beyond tolerance"
    if flag: out.append(pid)
    print(f"{pid:7s} {cat:18s} deviation {d:5.1f} mm (tolerance {tol:2d}){flag}")
print(f"{len(out)} of {len(points)} points beyond tolerance: {', '.join(out)}")
print("Each must show the engineer's disposition (accepted, modified or remediated) before the record is final.")

C-B2    column             deviation   3.6 mm (tolerance 12)
C-C3    column             deviation  10.0 mm (tolerance 12)
C-E7    column             deviation   9.8 mm (tolerance 12)
EP-01   embed plate        deviation   7.2 mm (tolerance 10)
EP-07   embed plate        deviation  13.3 mm (tolerance 10)  <- beyond tolerance
SL-M12  sleeve             deviation  10.0 mm (tolerance 25)
HD-14   hold-down coupler  deviation   5.8 mm (tolerance  6)
HD-15   hold-down coupler  deviation   9.1 mm (tolerance  6)  <- beyond tolerance
2 of 8 points beyond tolerance: EP-07, HD-15
Each must show the engineer's disposition (accepted, modified or remediated) before the record is final.

Six of eight points are within tolerance. Embed plate EP-07 at the stair landing is 13 mm out and hold-down coupler HD-15 is 9 mm out. The record must show what happened to each. In this case the steel fabricator slotted the stair connection to suit EP-07, with the structural engineer's approval, and the hold-down supplier confirmed that HD-15's rod could be installed with a coupler offset within the product's limits, which the engineer accepted. Both dispositions, with references to the approvals, go into the record. Sleeve SL-M12 appears at its revised position, 400 mm north of the original design, because the record shows the work as built, including the answered question that moved it.

Concealed work

Concealed work is where records matter most. Services inside walls, ceilings and slabs cannot be seen after closing, and the drawings rarely show their exact routing. Owners and future contractors want to know where pipes, conduits, tendons, hold-down rods and fire-stopping are located before they drill, cut or renovate.

Practical methods for recording concealed work include photographs of each wall and ceiling bay before closing, taken with a reference in the frame such as a gridline label or room number; 360-degree photo capture linked to floor plans, which lets anyone walk through the building as it was before closing; laser scans of complex areas such as mechanical rooms and corridor bulkheads; and survey of embedded items in slabs, such as conduits, floor boxes and tendons, before the pour. Post-tensioned slabs need special care: tendon locations should be recorded on the record drawings and, where the specification requires, marked on the slab soffit, because future coring without that information is dangerous (lesson 7).

The value of these records depends on organization. Thousands of photos without locations are almost useless. Platforms that pin photos to plan locations, and file naming that includes level, room and date, make the records searchable years later.

Record drawings and the record model

The final record drawings combine the posted working set, the redlines from each trade and the as-built surveys into a clean set that shows the work as built. The specification usually says what they must show, in what format and when they must be submitted. Typical requirements include changes from the contract drawings, actual locations of concealed services and their depths, dimensioned locations of underground utilities, and references to answered questions and change orders.

Increasingly, owners ask for a record model as well as drawings. The level of detail and accuracy required should be defined in the contract or the BIM execution plan (CON-260). A record model is valuable only if it is accurate where it matters; a model that shows services in their design positions when they were installed elsewhere is worse than no model, because people will trust it. The field engineer's surveys and scans are the main input for updating the model to the built condition.

Producing record documents takes time, and progress must be tracked like any other deliverable. Two months before substantial completion, Mei reviews the status of the record set.

# Record document status two months before substantial completion (invented data)
sheets = {  # discipline: (sheets in set, sheets with all changes posted, open items to post)
    "Architectural": (148, 121, 37),
    "Structural": (64, 61, 4),
    "Mechanical and plumbing": (72, 40, 58),
    "Electrical": (55, 33, 41),
    "Fire protection": (18, 18, 0),
    "Civil and landscape": (22, 15, 9),
}
tot = sum(v[0] for v in sheets.values()); done = sum(v[1] for v in sheets.values())
print(f"Overall: {done} of {tot} sheets current ({done / tot:.0%})")
for d, (n, ok, items) in sorted(sheets.items(), key=lambda kv: kv[1][1] / kv[1][0]):
    print(f"  {d:25s} {ok / n:4.0%} current, {items:3d} items to post")
weeks = 8
per_week = sum(v[2] for v in sheets.values()) / weeks
print(f"Items to post: {sum(v[2] for v in sheets.values())}, about {per_week:.0f} per week to finish in {weeks} weeks")

Overall: 288 of 379 sheets current (76%)
  Mechanical and plumbing    56% current,  58 items to post
  Electrical                 60% current,  41 items to post
  Civil and landscape        68% current,   9 items to post
  Architectural              82% current,  37 items to post
  Structural                 95% current,   4 items to post
  Fire protection           100% current,   0 items to post
Items to post: 149, about 19 per week to finish in 8 weeks

About three quarters of the sheets are current, but mechanical and electrical lag well behind, with nearly a hundred items still to post between them. At roughly 19 items a week across all disciplines, the backlog can be cleared in eight weeks only if the trades keep up. Priya raises record documents at the next subcontractor meeting, reminding the mechanical and electrical trades that their final payments and holdback release depend on complete records under the subcontracts.

Contractual and legal context

Record documents are usually a contract requirement for substantial or final completion, and incomplete records can delay final payment and the release of holdback. In British Columbia, the building permit process also relies on records: registered professionals provide letters of assurance confirming that the work substantially conforms to their designs, and they depend on field information to do so. Survey certificates from a British Columbia Land Surveyor may be needed to confirm the building's final position on the lot.

Records also matter for liability long after completion. In British Columbia, the Limitation Act generally sets a basic two-year limitation period from when a claim is discovered and an ultimate limitation period of 15 years for most claims, so a contractor may need to show how work was built many years later. Contractors should keep layout logs, survey data, inspection records and record documents for at least as long as their legal advisers recommend.

Honesty in records is a legal as well as an ethical duty. Records that were altered to hide deviations can expose the contractor and the individuals involved to serious liability if they come to light later, for example after a failure or during a dispute. The safest record is the true one, with each deviation and its disposition documented.

Handover to the owner

Handover is the transfer of the building and its information to the owner. For the field engineer, handover includes delivering the record drawings, the record model if required, the as-built surveys, the scan and photo archive, and the survey control information. Leaving the control information with the owner is often forgotten, but it is valuable: future additions, renovations and monitoring can use the same control if it is documented and preserved.

A short walk-through of the records with the owner's facility manager is good practice. Showing where to find tendon locations, how to search the photo archive and where the control points are makes it much more likely that the records will actually be used.