Washington, DC building code, answered.
The District's building-code authority center — plain-language answers on the code editions DC has adopted, the seal and submission rules, and the discipline thresholds that decide what a permit set needs.
Code basis: DC Construction Codes (2015 IBC with DC amendments).
Code basics & administration
Who must seal DC permit drawings? (architect/PE seal + residential exemption)
DC permit drawings involving the practice of architecture or engineering must be sealed by a DC-licensed architect or PE. Nonstructural alterations of R-3 residential buildings are exempt. Here is how the rule is layered.
ReadWhat building code does DC use? (2015 IBC, adopted editions)
DC uses the 2015 ICC family (2015 IBC/IMC/IPC/IFGC/IECC/IFC) with DC amendments and the 2014 NEC — not the 2017 or 2018 IBC. Here is the full adopted-edition table by discipline.
ReadBuilding & life safety
Who must seal DC permit drawings? (architect/PE seal + residential exemption)
DC permit drawings involving the practice of architecture or engineering must be sealed by a DC-licensed architect or PE. Nonstructural alterations of R-3 residential buildings are exempt. Here is how the rule is layered.
ReadIs R-38 + R-15 continuous insulation enough for a flat roof in DC?
Yes. And the R-15 exterior board isn't arbitrary — it's the IRC R806.5 condensation-control minimum for an unvented low-slope roof in DC's Climate Zone 4A. Here's the energy-code math, why flat roofs are built unvented, and why you must not add an interior vapor barrier.
ReadMechanical
When is duct leakage testing required in DC? (2015 IECC)
In DC, duct leakage testing is an energy-code requirement (2015 IECC §R403.3.3), not a building-code one. It applies when ducts or air handlers sit outside conditioned space. Here are the thresholds, the two exemptions, and the residential-vs-commercial split.
ReadIs R-38 + R-15 continuous insulation enough for a flat roof in DC?
Yes. And the R-15 exterior board isn't arbitrary — it's the IRC R806.5 condensation-control minimum for an unvented low-slope roof in DC's Climate Zone 4A. Here's the energy-code math, why flat roofs are built unvented, and why you must not add an interior vapor barrier.
ReadDoes a ventless kitchen hood still need IMC 507.3 in DC?
Yes. A 'ventless' listing addresses grease vapor (Type I) — it does not remove the IMC 507.3 heat/moisture obligation. DC offers three compliance paths, including a hoodless 0.70 cfm/sf make-up-air route.
ReadEnergy
When is duct leakage testing required in DC? (2015 IECC)
In DC, duct leakage testing is an energy-code requirement (2015 IECC §R403.3.3), not a building-code one. It applies when ducts or air handlers sit outside conditioned space. Here are the thresholds, the two exemptions, and the residential-vs-commercial split.
ReadIs R-38 + R-15 continuous insulation enough for a flat roof in DC?
Yes. And the R-15 exterior board isn't arbitrary — it's the IRC R806.5 condensation-control minimum for an unvented low-slope roof in DC's Climate Zone 4A. Here's the energy-code math, why flat roofs are built unvented, and why you must not add an interior vapor barrier.
Read