Page: Last modified: 2024-01-31
Code Reference(s):
NECB20 Div.C (first printing)
NECB20 Div.C 2.2. (first printing)
Alteration of Existing Buildings
Alteration of the Building Envelope
This proposed change adds administrative requirements related to the alteration of the building envelope.
This change could potentially affect the following topic areas:

General information

See the summary for subject Alteration of Existing Buildings.


Division C of the National Model Codes requires that the authority having jurisdiction (AHJ) be provided with adequate documentation and other information, such as drawings and equipment specifications, in order to verify compliance with the Code. With the introduction of the proposed requirements for the alteration of existing buildings in the NECB 2025, there will be a need for information and calculations related to the extent of the alterations.

Failure to provide adequate documentation and level of detail regarding the alterations would make it difficult for AHJs to verify that the proposed alterations conform to the Code. This situation could also lead to inconsistency in the design, construction and performance of the alterations, which could cause confusion and conflict between designers, manufacturers, AHJs and the legal community.

These conflicts would occur when

  • AHJs request documentation during permit reviews to prove Code compliance,
  • designers require Code compliance for use of their design specifications on a project, or
  • disputes arise which require litigation.


Providing administrative guidance in Division C on the proper reporting techniques for documentation and calculations related to the alteration of existing buildings for compliance with the NECB is necessary to ensure building officials are provided with an appropriate level of detail to assess Code compliance.


[] Terms

[1] 1)Words and phrases used in Division C that are not included in the list of definitions in Article of Division A shall have the meanings that are commonly assigned to them in the context in which they are used, taking into account the specialized use of terms by the various trades and professions to which the terminology applies.
[2] 2)Where objectives and functional statements are referred to in Division C, they shall be the objectives and functional statements described in Parts 2 and 3 of Division A.
[3] 3)Where acceptable solutions are referred to in Division C, they shall be the provisions stated in Parts 3 to 8, 10 and 1310 of Division B.
[4] 4)Where alternative solutions are referred to in Division C, they shall be the alternative solutions mentioned in Clause of Division A.

[2.2.] 2.2. Administration

[2.2.1.] 2.2.1. Administration

[] with Administrative Requirements

[2.2.2.] 2.2.2. Information Required for Proposed Work

[] Information Required
[] Calculations and Analysis
[] on the Building Envelope
[] on Lighting Systems
[] on HVAC Systems
[] on Service Water Heating Systems
[] on Electrical Power Systems and Motors
[] Requirements for Building Performance Compliance

[2.2.3.] -- Information Required for Alteration Work

[] ---General Information Required
[1] --)Sufficient information shall be provided to show that the proposed alteration will conform to this Code and whether or not it will affect adjacent property. (See Note A-
[2] --)Plans shall be drawn to scale and shall indicate the nature and scope of the proposed alteration and proposed occupancy in sufficient detail to establish that, when completed, the proposed alteration and the proposed occupancy will conform to this Code.
[3] --)If the proposed alteration is changed during construction, information on the changes shall comply with the requirements of this Section for alteration work.
[] ---Design Calculations and Analysis
[1] --)The calculations and analysis carried out in the process of ensuring conformity with the requirements of this Code shall be available for inspection upon request.
[] ---Documentation on the Alteration of the Building Envelope
[1] --)The following documentation on the alteration of the building envelope shall be provided:
[a] --)documentation on new or altered components, assemblies or systems in accordance with Article, and
[b] --)justifications and support documentation for the proposed air leakage rates of the air barrier system or air barrier assemblies of the areas of the building envelope subjected to alteration, in support of the exception permitted in Sentence (PCF 1857) of Division B.

Impact analysis

Administering the enforcement of the Code is the normal business of the existing enforcement infrastructure.

The enforcement of these administrative requirements is not expected to be time-consuming or add significantly to the workload that is the normal course of business for building inspectors. The overall impact would be a significant improvement in the ability of AHJs to successfully verify Code compliance.

Enforcement implications

The enforcement of the administrative requirements for the alteration of the building envelope in existing buildings can be accomplished with the same means and resources involved in the enforcement of Part 3 of the NECB.

However, there could be an increase in enforcement and permit-review responsibilities. Requiring information about alteration work would facilitate enforcement.

Who is affected

Designers, specification writers, manufacturers, contractors, building owners and building officials.

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