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ADU Pulse

Lexington ADU Permits

Detailed permit data from 2025

6
Total Permits
1
Completed
$172K
Avg Cost
$1.03M
Total Invested

Key Insights

DIY vs Contractor

DIY/Homeowner$71/sf avg
Contractor$338/sf avg

DIY ranges from $4/sf (internal separation) to $167/sf (new detached). Contractor ranges from $89/sf to $635/sf.

Type Breakdown

Detached2 permits
Attached/Conversion4 permits

Conversions dominate: 3 basement, 1 internal separation. Detached includes 1 ADU-over-garage at $635/sf.

Notable: $3,900 ADU

39 Woodpark Cir separated an existing addition (built after 1976) that already had a separate entrance. Minimal work to formalize as ADU. COO issued in 81 days.

All Permits

31A Bertwell Rd
B-25-470 · Submitted Apr 25, 2025
ActiveContractor
Cost
$511K
Size
805 sf
$/sf
$635
Bedrooms
2
Type
Detached
Subtype
New construction
Architect
No
HERS Rating
54
Builder
The Lagasse Group LLC (Natick, MA)
Description
Demo existing garage, construct new two story garage with apartment above including bathroom and kitchen. New utilities from existing home.
26 Douglas Rd
B-25-1530 · Submitted Nov 20, 2025
ActiveContractor
Cost
$251K
Size
862 sf
$/sf
$291
Bedrooms
1
Type
Attached
Subtype
Basement conversion
Architect
No
HERS Rating
—
Builder
International Construction & Development Inc (Milton, MA)
Description
Separate lower level from 1st floor to create ADU in lower level, partial gut rehab and install new kitchen. Mini splits for heating/cooling, new heat pump water heater.
302 Marrett Rd
B-25-1474 · Submitted Nov 6, 2025
ActiveDIY
Cost
$150K
Size
898 sf
$/sf
$167
Bedrooms
2
Type
Detached
Subtype
New construction
Architect
No
HERS Rating
53
Builder
Homeowner (hiring subs)
Description
New accessory dwelling unit
5A Solly's Way
B-25-1488 · Submitted Nov 11, 2025
ActiveContractor
Cost
$87K
Size
985 sf
$/sf
$89
Bedrooms
1
Type
Attached
Subtype
Basement conversion
Architect
No
HERS Rating
—
Builder
Kyle Matthew Construction LLC (Harvard, MA)
Description
Finish partially completed basement ADU from previous permit #B-24-1533. Finish basement entrance (doghouse).
Lower cost - finishing prior work
390 Marrett Rd
B-25-632 · Submitted May 30, 2025
ActiveDIY
Cost
$30K
Size
743 sf
$/sf
$40
Bedrooms
1
Type
Attached
Subtype
Basement conversion
Architect
Yes
HERS Rating
—
Builder
Homeowner (all work)
Description
Build ADU in the existing basement
Full DIY - likely just materials cost
39 Woodpark Cir
B-25-609 · Submitted May 24, 2025
CompleteDIY
Cost
$4K
Size
893 sf
$/sf
$4
Bedrooms
2
Type
Attached
Subtype
Internal separation
Architect
No
HERS Rating
—
Builder
Homeowner (all work)
Description
Separate existing addition (built after 1976) from main house to create ADU. Both already had separate entrances.
Minimal work - addition already existed with separate entrance
COO issued: Aug 13, 2025
Source: Town of Lexington Building Department permit records (2025)