Building Codes, Amendments & Division Policies

The Building and Code Compliance Division is responsible for:

  • Administering and enforcing the adopted International Codes, National Electric Code, and City Ordinances to ensure commercial and residential structures are built to standards that protect the health, safety, and welfare of the citizens and general public
  • Providing code and ordinance interpretations to citizens, contractors, and design professionals through consultation and informational handouts
  • Reviewing building applications and plans for compliance with ordinances and codes
  • Conducting Inspections of construction work requiring building permits to ensure the safety of the public and compliance with city ordinances and codes
  • Verifying qualifications of licensing of contractors
Building Codes

Code Books may be purchased from the International Code Council

Amendments
Design Criteria for IRC Only

Climate and geographic design criteria table

 

R-Values and U-Factors Table
This table shows the minimum R-values and maximum U-factors for different building assemblies in the City of Littleton, based on the 2024 International Codes. It includes separate requirements for commercial and residential construction.
CITY OF LITTLETON MIN. R-VALUES & MAX. U-FACTORS BY ASSEMBLY, BASED UPON THE 2024 I-CODES
Assembly IECC Commercial Provisions IRC & IECC Residential Provisions
Attics, Ceilings, & Roofs
Insulation entirely above roof deck R-30ci R-30ci
Metal bldgs. R-19 + R-11 LS Use Max. Assembly U-Factors from IECC Table R402.1.2 or IRC Table N1102.1.2
Attic/ceiling & other R-49 R-49b,c
Walls, above grade
Mass R-13.3ci for Group R
R-11.4ci for all other Groups		 R-13 where 50% or less insulation
on interior side of mass wall;
R-17 where more than 50% insulation
on interior side of mass wall
Metal bldg. R-13cav + R-14ci Use Max. Assembly U-Factors from IECC Table R402.1.2 or IRC Table N1102.1.2
Metal framed R-15.2ci only;
or R-13cav + R-10ci;
or R-20cav + R-9ci		 Use Max. Assembly U-Factors from IECC Table R402.1.2 or IRC Table N1102.1.2
Wood framed & other R-16ci only;
or R-13cav + R-7.5ci;
or R-20cav + R-3.8ci;
or R-27cav only		 R-20ci only;
or R-13cav + R-10ci;
or R-20cav + R-5ci;
or R-30cav only
Crawl space wall No value provided.
Use most applicable Wall value above.		 R-15ci only;
or R-13cav + R-5ci;
or R-19cav only
Walls, below grade
Below-grade wall R-10ci for Group R
R-7.5ci for all other Groups		 R-15ci only;
or R-13cav + R-5ci;
or 19cav only
Floors
Mass R-16.7ci for Group R
R-14.6ci for all other Groups		 No value provided.
Use most applicable Floor value below.
Joist/framing R-30 R-20ci;
or 19cav + R-7.5ci
or R-30cav only
Slab-on-grade floors
Unheated slabs R-20ci for 24″ below for Group R
R-15ci for 24″ below for all other Groups		 10ci for 3 ft
Heated slabs R-15ci for 36″ below grade on edges
+ R-5ci under full slab		 R-10ci for 36″ below grade on edges
+ R-5ci under full slab
Fenestration U-factors
Fixed windows 0.34 0.30
Operable windows 0.45 0.30
Glazed entrance doors 0.63 0.30
Skylights 0.50 0.50
Notes:
ci = continuous insulation; cav = cavity insulation; LS = linear system
a. This table is intended for use with the prescriptive energy conservation compliance pathways. It is a consolidated view of the values within the 2024 I-codes applicable to work within the City of Littleton. No values have been changed from those provided within the 2024 I-codes.
b. Applies to IRC & IECC Residential Provisions only - Ceilings with attics - Installing R-38 over 100% of the ceiling or attic area requiring insulation shall satisfy the requirement for R-49 insulation wherever the full height of uncompressed R-38 insulation extends over the wall top plate at the eaves.
c. Applies to IRC & IECC Residential Provisions only - Ceilings without attics - Where the design of the roof/ceiling assembly does not allow sufficient space for the required insulation within the interstitial space above the ceiling and below the structural roof deck, the minimum required insulation R-value for such roof/ceiling assemblies shall be R-30. Insulation shall extend over the top of the wall plate to the outer edge of such plate and shall not be compressed. This reduction of insulation from the requirements of Section R402.1.3 shall be limited to 500 sf or 20% of the total insulated ceiling area, whichever is less. This reduction shall not apply to the component performance alternative in Section R402.1.5.
d. Applies to IRC & IECC Residential Provisions only - For sunrooms and heated garages provided with thermal isolation, and enclosing conditioned space, the following exceptions to the insulation requirements of this code shall apply:
     1. The minimum ceiling insulation R-values shall be R-24.
     2. The minimum wall insulation R-value shall be R-13. Walls separating a sunroom or heated garage with thermal isolation from conditioned space shall comply with the building thermal envelope requirements of this code.
     3. The vertical fenestration U-factor shall not exceed 0.45. Fenestrations separating a sunroom or heated garage with thermal isolation from conditioned space shall comply with the building thermal envelope requirements of this code.
     4. The skylight U-factor shall not exceed 0.70.
e. For existing buildings, the R-values and U-factors must comply with the values in the table above only where new assemblies are provided, existing assemblies are modified, or there is a change-in-use. Where an existing assembly is exposed as part of the scope of work but the framing is not being replaced or modified, then the existing cavities should be filled with insulation to the greatest extent possible within the framing, not needing to exceed the values in the table above.

 

Building Division Policies

 

Building Division Newsletters

 

Contact Us

PERMIT CENTER

Permit Center
Call: 303-795-3751
Email: permits@littletonco.gov
FAX: 720-741-0210
eFax: 720-384-0601
Emails/voicemails should include the name, email/phone #, physical address, permit # (if applicable), and a detailed message.

Mon–Thurs: 8 a.m. to 4:30 p.m.
Fridays: Closed
In-person walk-in hours are limited to:

  • Monday: 1 to 4:30 p.m.
    * no walk ins accepted after 4:15 p.m.
  • Thursday: 8 to 11:30 a.m.
DEVELOPMENT REVIEW

Planning & Engineering
Call: 303-734-8076
Email: DRT@littletonco.gov

Book Your Appointment Online
or Submit a Question

Littleton Center
2255 W. Berry Avenue
Littleton, Colorado 80120
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