Three Phases, Three Different Realities
A building exists in three distinct versions: the design (what was intended by the engineers and architects), the construction (what was actually built by the contractor), and the operational reality (what exists today after years of use, modification and ageing). These three versions routinely differ from each other — sometimes significantly — and understanding the nature and extent of those gaps is critical for any meaningful building assessment.
Design Intent: What Was Specified
During design, engineers create drawings, specifications and calculations that define every aspect of the intended building. Structural engineers specify concrete grades (e.g., C30/37), reinforcement sizes and spacings (e.g., 16mm bars at 150mm centres), column dimensions and beam depths. MEP engineers specify electrical panel ratings, cable sizes, duct dimensions, pipe diameters and equipment capacities. Architects define spatial layouts, fire compartmentation boundaries and egress routes.
These design documents are submitted to RAJUK for approval and become the legal baseline for construction. They represent the professional engineer's intent — what would be built if every specification were followed exactly.
As-Built Reality: What Was Actually Constructed
Construction rarely matches design drawings exactly. Deviations occur for legitimate reasons (field conditions, approved change orders) and illegitimate reasons (cost-cutting substitutions, contractor convenience). Common categories of deviation include:
| System | Common Design-to-Construction Deviation | Potential Impact |
|---|---|---|
| Structural — concrete | Concrete grade changed (e.g., C30 specified, C25 supplied) | Reduced load-bearing capacity, reduced durability, accelerated carbonation |
| Structural — reinforcement | Rebar spacing increased or bar size reduced to save cost | Reduced flexural and shear capacity, non-compliance with design |
| Structural — cover | Concrete cover to reinforcement less than specified (e.g., 25mm instead of 40mm) | Accelerated carbonation reaching rebar, earlier corrosion initiation |
| HVAC | Duct routing changed due to coordination conflicts in ceiling voids | Changed pressure drops, reduced airflow to some zones, noise issues |
| Electrical | Cable sizes or circuit breaker ratings modified during installation | Changed fault current capacity, potential overloading, coordination issues |
| Fire protection | Sprinkler head spacing or type changed to suit ceiling conditions | Altered coverage patterns, potential non-compliance with NFPA 13 |
| Plumbing | Drainage routes modified to avoid structural elements | Changed slopes, potential drainage issues, different riser locations |
As-built drawings should record all deviations from the original design. They are typically prepared by the contractor at project completion, showing what was actually constructed using red-line markups on design drawings or fully revised drawing sets. In Bangladesh, as-built drawings are frequently not prepared, creating a critical documentation gap that makes future assessment significantly more difficult.
Operational Reality: What Exists Today
Over years of operation, buildings change further through tenant fit-outs, equipment replacements, system additions and unauthorised modifications. The operational building may differ substantially from both the design drawings and the as-built records (if they exist). Common operational modifications include:
- Partition walls added or removed — affecting fire compartmentation, structural loading and air distribution patterns
- Electrical loads increased — additional equipment, server rooms, kitchen facilities added without corresponding electrical infrastructure upgrades
- Fire doors propped open or removed — compromising fire compartmentation and smoke control strategies
- Ceiling voids used for storage or informal cable routing — adding unplanned loads and potentially compromising fire-rated ceiling systems
- Additional floors or mezzanines constructed — adding structural loads not accounted for in the original design
- Openings cut through structural elements — for new doors, windows, MEP routes or access points, potentially reducing structural capacity
How to Identify Discrepancies
The systematic method for identifying design-to-reality discrepancies involves:
- Document review: Obtain the latest available drawings (design, as-built or both) and compare them to each other for inconsistencies
- Site walkthrough: Physically compare drawings to the actual building — look for walls that appear on drawings but not on site (or vice versa), equipment that has been added or removed, and signs of modification
- Targeted verification: For critical elements (structural members, fire-rated assemblies, electrical distribution), use measurement, testing or opening-up to verify actual conditions
- Occupant interviews: Building management staff and long-term occupants often know about modifications that are not documented
Commissioning as Verification
ASHRAE Guideline 0 defines the commissioning process as systematic verification that building systems perform as designed. For new construction, commissioning verifies that installed systems match design intent. For existing buildings, ASHRAE Guideline 1.1 (HVAC&R Technical Requirements for the Commissioning Process) and retro-commissioning processes verify that systems are performing as intended — or identify where they are not.
Commissioning reports that compare design specifications to measured performance provide some of the most valuable evidence of design-to-reality gaps.
Metrics: Scale of Design-to-Reality Gaps
| Metric | Industry Finding | Source / Basis |
|---|---|---|
| Systems differing from design specifications | 10–30% of installed systems differ from design in typical projects | Industry commissioning experience; ASHRAE research |
| Buildings without as-built drawings | Estimated majority of pre-2010 buildings in Bangladesh | Local industry observation Editorial verification required |
| Unauthorised modifications per decade of operation | Multiple per floor in multi-tenant commercial buildings | Property condition assessment experience |
| Concrete cover deficiency rate | 30–50% of elements may have cover less than specified | Cover meter survey findings in regional construction |
Practical Considerations
Perfect alignment between design, construction and operational reality is rare. The practical question is not whether gaps exist but whether they are known, documented and assessed for significance. A concrete grade one step below specification may be acceptable with a revised capacity check. An undocumented structural modification may or may not be adequate — but without assessment, it is an unknown risk.
For buildings with no as-built drawings and a history of modifications, the only reliable approach is a current-condition survey: physically documenting what exists today and assessing it against current code requirements, rather than attempting to verify compliance with original design documents that may never have been faithfully executed.
Insights & Guidance
- Design drawings represent intent, not necessarily reality — construction deviations and operational modifications create cumulative gaps
- Common construction deviations include concrete grade changes, rebar spacing modifications, reduced cover depths and re-routed MEP systems
- Operational modifications (partition changes, load increases, fire door removal, additional floors) compound the gap between documents and reality
- As-built drawings should record all construction deviations but are frequently absent in Bangladeshi buildings
- ASHRAE Guideline 0 commissioning provides systematic verification of design intent versus installed performance
- When documentation is unreliable or absent, current-condition survey against current codes is the pragmatic approach
- Original RAJUK-approved design drawings showing the intended building
- As-built drawings showing actual constructed conditions and all deviations from design
- Construction inspection reports documenting any approved changes during construction
- Commissioning reports comparing design specifications to measured system performance
- Tenant fit-out approval records and drawings for each modification
- Modification records with engineering assessments for any post-construction structural changes
- Current condition survey or Property Condition Assessment (ASTM E2018) if documentation is incomplete
- Walls or partitions that appear on drawings but not on site, or vice versa — indicating undocumented modifications
- Evidence of structural modifications: infilled openings, new openings cut, visible patching around columns or beams
- Electrical distribution boards with circuits added beyond original panel capacity, or additional sub-panels installed
- HVAC diffusers blocked, relocated or supplemented with portable units — suggesting the original design no longer meets current needs
- Fire doors propped open, removed or replaced with non-rated doors
- Signs of additional loading: storage on mezzanines, heavy equipment on floors not designed for it, water tanks added to roof
- Cable trays, pipes or ducts that clearly post-date the original construction (different materials, mounting methods or routing)
- Have as-built drawings been prepared, and are they available for all disciplines?
- Has the building been modified since original construction, and are those modifications documented?
- Were construction inspection reports prepared, and do they record any deviations from design?
- Has a commissioning or retro-commissioning exercise been conducted to verify system performance against design?
- Are there tenant fit-out records showing what modifications each tenant has made?
- Has any structural element been modified, penetrated or had its loading changed since original design?
- Has the fire compartmentation strategy been verified against current site conditions?
- Are the current electrical loads within the capacity of the original electrical design?