265days until every Maine
municipality must comply

One date statewide, set by LD 2173

Build 3-4 Units on Any Residential Lot

No owner-occupancy rule or planning-board review from July 2027; save $15K–$40K on sprinklers

Jump to investor benefits, developer rules, or common questions

What Changed — LD 2003 vs LD 1829

LD 1829 builds on LD 2003's foundation but removes the discretion municipalities used to delay or limit ADU development. Most of these changes take effect July 1, 2027.

Comparison of Maine LD 2003 (2022) and LD 1829 (2025) ADU law changes
Feature	LD 2003 (2022)	LD 1829 (2025)	What This Means
Units per lot	2 (primary + 1 ADU)	3 minimum statewide; 4 in growth areas with public water + sewer	Double the density on every residential lot
Owner occupancy	Varied by municipality	Barred statewide from July 1, 2027	Build an ADU and rent both units — investment property enabled
Fire sprinklers	Municipality discretion	Cannot require for structures with ≤2 dwelling units	Saves $15K–$40K per unit
Subdivision review	Triggered at 3 units	Triggered at 5+ units within a 5-year period	Build 3–4 units without subdivision process
Planning board	Required for some projects	Not required for ≤4 units	Administrative approval only — no public hearing required
Multifamily ADUs	Single-family lots only	ADUs on multifamily lots too	Expanded eligibility
Lot size (growth areas)	Municipality discretion	5,000 sq ft minimum	Smaller lots can participate
Lot size (non-growth areas)	Municipality discretion	10,000 sq ft minimum (per LD 2173; MOCA guidance pending)	Larger lots required outside growth areas
Rate of growth ordinances	Allowed	Permitted (105% of 10-year average)	Affordable housing exempt from caps

Units per lot

Before

2 (primary + 1 ADU)

After

3 minimum statewide; 4 in growth areas with public water + sewer

Impact

Double the density on every residential lot

Owner occupancy

Before

Varied by municipality

After

Barred statewide from July 1, 2027

Impact

Build an ADU and rent both units — investment property enabled

Fire sprinklers

Before

Municipality discretion

After

Cannot require for structures with ≤2 dwelling units

Impact

Saves $15K–$40K per unit

Subdivision review

Before

Triggered at 3 units

After

Triggered at 5+ units within a 5-year period

Impact

Build 3–4 units without subdivision process

Planning board

Before

Required for some projects

After

Not required for ≤4 units

Impact

Administrative approval only — no public hearing required

Multifamily ADUs

Before

Single-family lots only

After

ADUs on multifamily lots too

Impact

Expanded eligibility

Lot size (growth areas)

Before

Municipality discretion

After

5,000 sq ft minimum

Impact

Smaller lots can participate

Lot size (non-growth areas)

Before

Municipality discretion

After

10,000 sq ft minimum (per LD 2173; MOCA guidance pending)

Impact

Larger lots required outside growth areas

Rate of growth ordinances

Before

Allowed

After

Permitted (105% of 10-year average)

Impact

Affordable housing exempt from caps

Check if your zone allows 3-4 units

When It Takes Effect

July 1, 2027

265 days

Set by LD 2173 (Public Law 2026, chapter 733)

Every Maine municipality

LD 1829 originally took effect July 1, 2026 where municipal officers can enact ordinances without a vote, and July 1, 2027 everywhere else. LD 2173 replaced that with this single date.

3 Units vs 4 Units

3 units by right on any residential lot statewide. 4 units only if the lot is in a designated growth area AND connected to public water AND public sewer. Many “growth areas” lack town sewer, which caps the lot at 3 units.

Who Benefits

Homeowners

•From July 1, 2027: no owner-occupancy requirement — build and rent without living on-site
•Build for aging parents, adult children, or rental income
•ADU rental income can improve loan-to-value ratios
•Fannie Mae now allows projected ADU rental income for mortgage qualification

Investors

•Single-family lots become 3–4 unit properties
•Fire sprinkler savings: $15K–$40K per unit
•Portland metro ADU rents: ~$1,200–$1,500/mo per unit
•Administrative-only approval — no planning board hearing

Developers

•Subdivision threshold raised to 5+ units (5-year lookback)
•Growth area height bonus: +14 ft above local limits
•Minimum lot size: 5,000 sq ft in growth areas
•Rate of growth ordinances: 105% of 10-year avg, affordable housing exempt

Browse 263 ADU-eligible models

$15K–$40K

Potential fire sprinkler savings per unit under LD 1829

How Much Does It Cost?

Typical 600 sq ft ADU — from 263 purchasable models across 14 builders

Kit Package

Framing & exterior shell only

$40,000–$80,000

Shell Package

Weathertight, ready for interior

$80,000–$150,000

Turnkey Package

Move-in ready

$150,000–$400,000+

Watch for the completion gap

A $100K kit becomes $200K–$300K+ after site work, foundation, utilities, and interior finish. Site conditions alone can add $30K–$70K+.

Get a personalized cost estimate

Common Questions About LD 1829

No, for most ADU projects. Under LD 1829, municipalities cannot require fire sprinklers for residential structures with 2 or fewer dwelling units. If your property has 3 or more dwelling units total, sprinkler requirements may still apply. The estimated savings are $15,000–$40,000 per unit.

Yes, starting July 1, 2027, in every Maine municipality. LD 2173 replaced LD 1829’s original two-date schedule with that single date. LD 1829 establishes a statewide minimum of 3 dwelling units on any residential lot. In designated growth areas with public water and sewer, you can build up to 4 units.

Yes. LD 1829 is state law and supersedes local ordinances on the issues it addresses. Municipalities have received DECD grants to help update their ordinances.

Designated growth areas are defined in each municipality's comprehensive plan. Being in a designated growth area alone is not sufficient for the 4-unit allowance: the lot must also be connected to public water AND sewer systems. Many areas designated as "growth areas" lack town sewer — in those cases, the lot is capped at 3 units.

Not yet. From July 1, 2027, LD 1829 bars towns from requiring owner-occupancy for ADUs (30-A M.R.S. §4364-B(4)(E)). Until then, your town may still require it, so check its ordinance. After that date you can build an ADU — or multiple units — and rent all of them without living on the property.

LD 1829 does not address short-term rentals. From July 1, 2027 it bars owner-occupancy requirements for long-term residential use, but it does not override municipal short-term rental regulations. Check your local STR ordinance separately.

LD 2003 (2022) legalized ADUs statewide but gave municipalities significant discretion. LD 1829 (2025) removes that discretion, most of it from July 1, 2027: 3–4 units by right, no owner-occupancy, no fire sprinklers for structures with ≤2 dwelling units, administrative-only approval for ≤4 units, and a subdivision threshold raised from 3 to 5 units.

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What to Do Next

Check Your Zone

Enter your address on our interactive zoning map to see your zone's dimensional standards, ADU eligibility, and LD 1829 impact.

Check Your Zone

Find Models That Fit

Browse ADU-eligible prefab models for Maine from manufacturers serving New England. Filter by size, bedrooms, price, and service level.

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Estimate Your Cost

Use our Cost Estimator with actual manufacturer pricing to understand the full project cost — including the gap between base price and finished home.

Estimate Your Cost

This guide is for informational purposes only and does not constitute legal advice. Zoning regulations are complex and subject to municipal interpretation. Consult a qualified attorney or your local planning office for guidance specific to your property.

Sources & References

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