Aircraft/spacecraft hangars (also known as “hangars”) include buildings or structures designed to maintain, store, and protect aircraft (i.e. commercial aircraft, military aircraft, planes, helicopters, etc.) and/or spacecraft (i.e. launch vehicles, crewed vehicles, robotic probes, etc.).
Hangars are structurally distinct structures known for their enormous size, massive clear-span framing, colossal doors, enhanced fire suppression systems, and heavily reinforced foundations.
Famous aircraft/spacecraft hangars include: NASA’s Kennedy Space Center (KSC) Space Systems Processing Facility (SSPF); NASA’s Marshall Space Flight Center (MSFC) Michoud Assembly Facility (MAF); and The Chicago O’Hare International Airport American Airlines’ Hangar 2.
Aircraft hangars are generally classified based on functionality and with respect to National Fire Protection Association (NFPA) Standard on Aircraft Hangars, NFPA 409.
Key NFPA 409 Fire Protection Classifications include:
- Group I: Largest facilities; single fire area of 40,000 sq ft (3,716 sq m) or more
- Group II: Medium-sized facilities; single fire area between 12,001 and 40,000 sq ft.
- Group III: Smaller facilities; single fire area of 12,000 sq ft or less.
- Group IV: Specific membrane-covered, rigid steel frame
Key Functional & Design Aircraft Hangar Classifications include:
- T-Hangars
- Box/Community Hangars
- Maintenance, Repair, and Overhaul (MRO) Hangars
- Corporate/Fixed Base Operator (FBO) Hangars
- Military Hangars
Similarly, spacecraft hangars are classified by their operational environment (terrestrial vs. extraterrestrial), functionality, and scale.
Key Functional & Design Spacecraft Hangar Classifications include:
- Vertical Assembly/Integration Hangars (i.e., the Vehicle Assembly Building)
- Horizontal Processing Hangars
- Mobile Service/Transport Hangars
Hangars include Reinforced Concrete structures (i.e., hardened hangars), Pre-Engineered Metal Buildings (PEMBs), and conventional steel buildings (CSBs). That said, due to their size and complexity—which includes large clear-span roofs, oversized doors, high wind exposure, fire-protection complexity, aircraft fuel hazards, corrosion exposure, crane/hoist loads, and operational impact risks—hangars have distinct design requirements.
Governing aircraft/spacecraft hangar design codes and standards include the International Building Code (IBC), the American Society of Civil Engineers (ASCE), “Minimum Design Loads and Associated Criteria for Buildings and Other Structures” (ASCE 7), the American Institute of Steel Construction (AISC) Steel Construction Manual, the American Concrete Institute (ACI) Building Code Requirements for Structural Concrete (ACI 318), the National Fire Protection Association (NFPA) Standard on Aircraft Hangars (NFPA 70).
Similarly, while aircraft hangars must also comply with Federal Aviation Administration (FAA) Advisory Circulars (AC 150/5300) and local airport authority minimum standards, spacecraft hangars must comply with the Unified Facilities Criteria (UFC) Standards UFC 4-211-01N/UFC 4-211-01 and other applicable codes.
Hangar new builds and/or renovations (in existing buildings) can be tricky for General Contractors.
Below are the top 5 structural blind spots in Hangar Renovation for General Contractors.
For construction defects or design defects involving structural components, it is generally advisable to engage construction-defect and structural forensic engineering experts early on in the case to determine causation, reduce risks, and limit costs.
Preeminent Solutions is a WOSB-certified, DBE-certified, MWBE-certified, LDB-certified, and soon-to-be 8(a)-certified civil/structural engineering firm specializing in structural forensics and construction-defect expert witness work.
Contact us for your next aircraft and/or spacecraft hangar renovation project.
onding/Poor Roof Drainage
Hangars, and correspondingly hangar roofs, cover considerable amounts of surface area.
For reference, the smallest NFPA 409 Single Fire Area, corresponding to Type V(000) Construction, consists of a surface area of 5,000 sq-ft (465 m²) or more.
Large building areas require large building roof areas, which in turn require sufficient drainage via internal gravity drain systems, siphonic roof drain systems, scuppers, external gutters, and/or other means.
Key structural warning signs of poor roof drainage include:
- Roof Ponding
- Sagging Roof Decks
- Water Intrusion at or Near Mechanical/HVAC Penetrations
- Rusted Roof Connections and Fasteners
- Standing water that remains for 48 hrs or more after precipitation
- Rust and Corrosion of Steel Metal Components
- Visibly Sagging Roof Deck
- Sagging Steel Joists
- Separated Roof Deck Panels
- Rust Stains
- Anchor Bolt Corrosion
Furthermore, larger roofs, and in particular large flat roofs, require sufficient drainage to prevent ponding issues, overloading, and deterioration of the structure.
Debris blockage, insufficient slope, and/or deformed underlying framing elements can exacerbate ponding issues, leading to leaks and further deterioration of the roof structure.
Key Signs of ponding issues in flat commercial roofs include:
Excessive water weight from ponding loads provides a serious threat to existing structures and may lead to further structural damage, leaks, and roof failure.
The above issues are especially relevant in the retrofit of older structures.
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding ponding issues:
Link: https://psengrinc.com/learning/
Contact a qualified mechanical engineer if your structure displays any of the above signs of poor drainage.
Contact a qualified structural engineer if your structure displays any of the above signs of ponding or other structural issues.
Water Intrusion
During hangar renovation, existing structures may be more susceptible to water intrusion.
Excessive water intrusion can damage framing elements and lead to corrosion in steel elements.
Key signs of water intrusion include:
- Efflorescence in Concrete Structures
- Rust Staining in Reinforced Elements
- Rotted Frame Elements
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural performance:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of water intrusion.
Demolition-Induced Instability
Hangar renovation-related demolition can uncover a host of underlying issues in existing structures.
Excessive demolition without appropriate temporary shoring can destabilize sections of existing structures.
Note: Structural instability is a threat to life and must be addressed immediately.
Key signs of structural instability due to demolition include:
- Rapidly Expanding Cracks
- Diagonal Cracks in Concrete Beams
- Diagonal Cracks in Concrete Walls
- Stair-step Cracking in Masonry Walls
- Widening Vertical Tension Cracks in Load-Bearing Elements
- Severe Horizontal Cracking and Bulging in Masonry Walls
- Cracks Radiating from Corners of Windows and Doors
- Crushed or Spalling Concrete around Compressed Zones
Key signs of roof or slab discontinuity due to demolition include:
- Sagging Roof Lines near Cut Zones
- Dipping Roof Ridges near Cut Zones
- Rafter Separation from Supporting Walls
- Truss Separation from Supporting Walls
- Buckled Metal Deck Panels
- Sheared Fasteners
- Torn Flashing at Transition Joints
- Severe Diagonal Concrete Cracking in Slabs
- Spalling or Chipping of Concrete
- Rusting Steel Reinforcement
- Concrete Slab Efflorescence on the Slab Underside
- Rust Stains Bleeding through Concrete Pores
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding structural performance:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of structural instability.
Slab Cracking and Subgrade Issues
Hangar foundation slabs span relatively large areas and must withstand high and concentrated loads repeatedly without failure.
While in operation, hangar foundation slabs may show signs of cracking.
Key causes of hangar foundation slab cracking may include:
- Concrete Slab Shrinkage
- Concrete Curling (i.e. the Upward/Downward Bending of the Corners of Slab)
- Aircraft/Spacecraft Vehicle Loads
- Structural Settlement
- Thermal
Some cracking may be serviceability-related, while other cracks indicate insufficient capacity or subgrade problems.
Key signs of subgrade problems in concrete foundation slabs include:
- Diagonal/Shear Cracking at Slab Corners
- Sloping Floors
- Uneven Transitions
- Rocking or Hollow Slabs
- Visible Slab Sinking
- Severe Concrete Cracking
- Concrete Spalling
- Concrete Delamination
- Pooling Water
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding foundation issues:
Link: https://psengrinc.com/learning/
Contact a qualified structural engineer if your structure displays any of the above signs of slab or foundation capacity issues.
Foundation Settlement and Differential Movement
Hangar renovation changes including demolitions, heightened vibration loading, overloading, and additions, may negatively impact the structure’s foundation resulting in differential settlement.
Key signs of differential settlement include:
- Structural Cracks at Building Corners
- Structural Cracks at Building Openings
- Sloping or Uneven Floors
- Separations of Main and Auxiliary Structures
Cracking patterns must be carefully mapped to separate old movement from new renovation construction-caused movement.
Consult Preeminent Solutions’ Free Online Education Center for resources and checklists regarding differential settlement:
Link: https://psengrinc.com/learning/
Contact a qualified structural forensic expert and a qualified geotechnical expert should the subject structure display any of the above signs of differential settlement.
Preeminent Solutions is a DBE-certified, MWBE-certified, LDB-certified and soon to be 8(a)-certified and WOSB-certified, civil/structural engineering firm.
We have over 30 years’ experience in civil/structural design, forensics, and expert work
We’re Licensed in CA, FL, TX, NJ, NY, DC, MD, VA, TN, MS, GA, NC, SC, LA, & more.
Reach out if your team is in need of structural engineering support.
Preeminent Solutions, Inc.
Forensic Structural Engineers & Consultants
📞 (321) 244-8699 | (407) 901-0133
✉️ info@psengrinc.com
🌐 www.psengrinc.com
