Updated: Jul 02, 2026
Location and Projects
Address
17700 S AVALON BLVD #345, Carson, CA, 90746
Use our bidding system to
request a quote
Twenty One Retrofit Construction
Serving the greater Los Angeles area from its base in Carson, Twenty One Retrofit Inc specializes in seismic retrofitting for multifamily and commercial buildings. The company focuses on soft-story earthquake retrofitting, helping property owners meet local seismic safety requirements. Twenty One Retrofit Inc has experience with projects involving apartment complexes and mixed-use buildings, addressing foundational reinforcement and structural upgrades as mandated by city ordinances. Their portfolio demonstrates work completed in neighborhoods across Los Angeles, reflecting familiarity with jurisdictional guidelines and permit processes. With over six years in business, Twenty One Retrofit Inc is regularly engaged by property management firms and building owners looking to improve their structures’ earthquake resilience. The company manages all phases of the retrofit process, from engineering consultation and permitting to construction and city inspections.
Twenty One Retrofit Inc Services
Start a project today:
Twenty One Retrofit Inc Contact Information
Phone Number: (213) 999-6286
Edit
Address: 17700 S AVALON BLVD #345, Carson, CA 90746
Edit
Do you work for this business? Unlock this free profile to update company info and see who's viewing your profile.
Twenty One Retrofit Inc Carson
Quality
102
89th percentile
Pro tip:
We generally recommend hiring a contractor with a score higher than 95.
Twenty One Retrofit Inc has a BuildZoom score of 102, which places them above 89% of 336,931 contractors in California.
Activity
|
2 projects
|
2025 |
|
4 projects
|
2024 |
|
13 projects
|
2023 |
Our building permit records indicate that Twenty One Retrofit Inc has worked on at least
19.0 projects over the past 3 years.
This is an overview of this contractor's activity. Click here to access our complete licensing and building permit database.
This is an overview of this contractor's activity. Click here to access our complete licensing and building permit database.
Pricing
|
4 projects
|
< $5k |
|
5 projects
|
$20k-$50k |
|
3 projects
|
$50k-$100k |
The typical size of their permits is approximately $25,000. This graph shows the distribution of these job values.
Pro tip:
For more details about their pricing, check out their recent activity to see how much they have charged for different types of work.
Building Permits by Twenty One Retrofit Inc
This is a sample of this contractor's permits. Click here to access their complete permit history.
Supplemental permit to #24016-10000-34893 to change work description to: (1) door change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24 comply with department order effecti... see more
Valuation:
N/A
Permit #:
24016-10001-34893
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
(1) window change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24. comply with department order effective date 03/22/2022. permit will expire 30 days from issuance date
Valuation:
$1,000
Permit #:
24016-10000-34893
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Windows (5) change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24
Valuation:
$3,000
Permit #:
24016-30000-33790
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Windows (5) change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24
Valuation:
$3,000
Permit #:
24016-30000-33788
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Mostly interior remodel of two units of triplex including alteration of kitchens and bathrooms and replacing some exterior doors in existing frames. plumbing and electrical work under separate permit
Valuation:
$80,000
Permit #:
22016-10000-01942
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
2 window change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24. comply with department order effective date 08/10/2022. permit will expire 30 days from issuance date
Valuation:
$3,000
Permit #:
23016-10000-44009
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
(2) window and (1) door change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24. comply with department order effective date 04/11/2022. permit will expire 30 days from issua... see more
Valuation:
N/A
Permit #:
23016-10000-18115
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
1- window change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24. comply with department order effective date 08/06/2021. permit will expire 30 days from issuance date
Valuation:
$2,000
Permit #:
23016-10000-08253
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Supplemental to 21042 10000 84878 to change address from 1800 n kingsley dr to 1802 1802 1/2 1804 1804 1/4 1804 3/4 1804 1/2 1806 kingsley dr washer and dryer additions in 7 units 1802 1802 1/2 1804 1804 1/4 1804 3/4 1804 1/2 1806 tankless water heater 1806
Valuation:
N/A
Permit #:
21042-10001-84878
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
(10) window change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24
Valuation:
$8,000
Permit #:
21016-10000-21266
Status:
final
Fee:
N/A
Permit Type:
1 or 2 family dwe...
Building Type:
N/A
(6) window change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24
Valuation:
$3,000
Permit #:
21016-10000-21256
Status:
final
Fee:
N/A
Permit Type:
1 or 2 family dwe...
Building Type:
N/A
(4) window change-out (same size & type) for residential buildings. dual glazing labeled and certified by national fenestration rating council (nfrc) is required for doors and windows replaced in all residential buildings three stories or less per section 150.2(b) 1b of title 24
Valuation:
$2,000
Permit #:
21016-10000-21263
Status:
final
Fee:
N/A
Permit Type:
1 or 2 family dwe...
Building Type:
N/A
Eplan: soft-story seismic retrofit per labc chapter 93: install special steel cantilever column at west elevation and exempt south wall line tuck under parking area due to existing concrete floor above garage area
Valuation:
$40,000
Permit #:
23016-10000-06529
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Supplemental to 19016-10000-20873; to revise soft story retrofit foundation and framing plan details
Valuation:
$50,000
Permit #:
19016-10002-20873
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Soft-story retrofit as per labc ch 93. supplemental permit to #18016-10000-22423 to revise foundation for (n) omf
Valuation:
$501
Permit #:
18016-10002-22423
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Soft story retrofit as per labc ch 93. supplemental permit to 20016-10000-02031. changes in foundation and framing plan details to field conditions
Valuation:
$501
Permit #:
20016-10001-02031
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Eplan: soft-story seismic retrofit per labc chapter 93: install new special steel cantilever column
Valuation:
$25,000
Permit #:
22016-10000-21432
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
(b) permit to subdivide unit s into 2-units (unit s-1, 072 sf - new unit t-1, 488 sf); demising wall demolish one restroom & upgrade remaining restroom and addition urinal new storefront
Valuation:
N/A
Permit #:
BLD22-002428
Status:
final
Fee:
$677
Permit Type:
Commercial
Building Type:
N/A
Soft-story seismic retrofit per labc chapter 93: install one (1) two ways special steel cantilever column
Valuation:
$30,000
Permit #:
22016-10000-39206
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Laundry vents in (5) units 1802 ½ 1804 1804 ¼ 1806 1802
Valuation:
N/A
Permit #:
22044-10000-15248
Status:
final
Fee:
N/A
Permit Type:
Apartment
Building Type:
N/A
Similar Contractors See more
185
BZ Score
$9.9K
Avg Project
-
Projects
212
BZ Score
$40K
Avg Project
-
Projects
192
BZ Score
$27.9K
Avg Project
-
Projects
Twenty One Retrofit Inc Reviews
BuildZoom hasn't received any reviews for Twenty One Retrofit Inc. Click here to be alerted when reviews are posted about them.
Recent Buildzoom Projects
Hiring a contractor?
Verified License
BuildZoom confirmed this contractor's license
Twenty One Retrofit Inc License info
Verified License
| License # | 1141855 |
| Status | Active |
| State | California |
| Type | General Building, Steel, Structural |
| Date Issued | 08-11-2025 |
| Business Type | Corporation |
- BuildZoom verified this license was active as of February 2026.
Verify this license's status for Twenty One Retrofit Inc at the California Contractors State License Board.
This is a sample of licensing data; click here to access a complete history.
Inactive License
| License # | 1065687 |
| Status | Inactive |
| State | California |
| Type | General Building, Steel, Structural |
| Business Type | Corporation |
- According to the California Contractors State License Board, the status of this license was at one point cancelled. However, this information may have changed. If this is your business, please update your license status.
Check this license's status for Twenty One Retrofit Inc at the California Contractors State License Board.
This is a sample of licensing data; click here to access a complete history.
102
BuildZoom Score
Bonded
| Bonded Agent | This License Filed A Contractor's Bond With |
| Bond Value | $15,000 |
Insured
| Workers Comp Provider | Berkshire Hathaway Direct Insurance Company |
30
Permits
- Building permit records show that Twenty One Retrofit Inc has worked on 30 permitted projects.
Twenty One Retrofit Inc Employees
TK
Tony Jeong Kim
Rmo / Ceo / Pres