Maine Code · The Foundation
The Maine Uniform Building and Energy Code (MUBEC), Explained
MUBEC is Maine's single statewide building and energy code. It decides what a new Maine home must be — and, through its existing-building provisions, what your renovation must become. This page covers what MUBEC is, the statutes behind it, which model codes it adopts, where it applies, and who enforces it.
The legal framework
One code for the whole state, created by statute
Before 2010, building codes in Maine were a town-by-town patchwork. The Legislature ended that by creating a single mandatory statewide code — the Maine Uniform Building and Energy Code — and a technical board to maintain it. The core legal machinery lives in Title 10 of the Maine Revised Statutes:
§9721 establishes the Maine Uniform Building and Energy Code. §9722 charges the Technical Building Codes and Standards Board (established under 5 M.R.S. §12004-G) with adopting, amending, and maintaining MUBEC from the national model codes — and, since 2021 legislation, with adopting and maintaining a more stringent stretch code as an appendix. §9724 governs application and enforcement: MUBEC applies statewide, and municipalities meeting the population threshold must enforce it.
Title 25, chapter 314 places the Bureau of Building Codes and Standards within the Department of Public Safety (the State Fire Marshal's Office administers MUBEC). Title 30-A, §4451 establishes the training and certification of municipal code enforcement officers and of the certified third-party inspectors that towns may use to conduct MUBEC inspections.
The adopted code itself lives in the board's rules: Chapter 1 (administration, scope, enforcement, exemptions), chapters adopting the building, residential, and existing-building codes with Maine amendments, and Chapter 6, the Maine Uniform Energy Code (MUEC), which adopts the IECC with Maine amendments and designates the stretch code. These rules — with every Maine-specific amendment — are published by the State Fire Marshal's Office at maine.gov/dps/fmo/building-codes.
What's inside MUBEC
The model codes Maine has adopted — 2021 editions, effective April 7, 2025
MUBEC is a package of national model codes and standards adopted by reference, with Maine amendments. State law (10 M.R.S. §9722) requires Maine to stay within two editions of the current model codes, and in 2024 the board voted to update from the 2015 editions. Since April 7, 2025, the following editions are in effect statewide:
| Code / Standard | Edition | What it governs for a Maine home |
|---|---|---|
| International Residential Code (IRC) | 2021 | One- and two-family dwellings and townhouses — structure, framing, and (in Chapter 11) energy provisions mirroring the IECC |
| International Building Code (IBC) | 2021 | All other buildings, including larger multifamily |
| International Energy Conservation Code (IECC) | 2021 | The energy code: insulation R-values, air leakage, ducts, ventilation-related energy provisions — for new work and for additions, alterations, repairs, and changes of occupancy (Chapter 5 [RE]) |
| International Existing Building Code (IEBC) | 2021 | Repair, alteration, addition, and change of occupancy of existing buildings — including when energy compliance is required (§§708, 809, 907) |
| International Mechanical Code (IMC) | 2021 | Mechanical systems in buildings other than 1–2 family dwellings |
| ASHRAE 62.1 / 62.2 | 2019 | Ventilation — commercial (62.1) and residential (62.2), the "ventilate right" half of build-tight-ventilate-right |
| ASHRAE 90.1 | 2019 | Energy standard for buildings other than low-rise residential (alternative commercial path) |
Maine also adopts referenced ASTM standards and maintains Maine-specific amendments to each code — always check the Fire Marshal's published amendment chapters. Radon (Appendix F) and other Maine appendix choices apply as designated by the board.
The stretch code
Under 10 M.R.S. §9722, the board also maintains the MUBEC Stretch Code — currently the 2021 IECC's efficiency appendices (RA/RB/RC residential; CA/CB/CC commercial) — a more stringent option that municipalities may adopt as their base energy code. Portland, South Portland, and Freeport were early adopters of stretch-level requirements; if you build or renovate in a stretch-code town, the bar is higher than the base numbers on our new construction page. No municipality may enforce any building code other than MUBEC or the MUBEC stretch code — that's the "uniform" in the name.
Where and to whom it applies
MUBEC applies to every Maine building — enforcement varies by town size
This is the most misunderstood point in Maine construction, so here it is plainly:
- MUBEC applies statewide. It is the legal construction standard for buildings constructed or renovated anywhere in Maine, regardless of the town's size.
- Enforcement is mandatory in municipalities with 4,000 or more residents. Those towns must inspect and enforce, using trained code enforcement officers or certified third-party inspectors (30-A M.R.S. §4451).
- Towns under 4,000 may choose whether to enforce. But choosing not to inspect does not repeal the code — the MUBEC standard still applies to the building. Builders remain obligated to build to it, insurers and lenders may require proof of it, and it becomes the reference standard in disputes and at resale.
- Certain buildings are exempt from parts of MUBEC. Notably, MUBEC Chapter 1 exempts qualifying seasonal dwellings (small, owner-occupied camps meeting strict limits on size, heating, and services) from the energy code's requirements. Converting such a camp to year-round use ends the exemption — one of the classic code-triggered upgrade scenarios we cover in depth.
Who your "AHJ" is
Your Authority Having Jurisdiction is your municipal code enforcement office (or its contracted third-party inspector). They issue permits, choose inspection methods allowed under MUBEC Chapter 1, interpret gray areas, and sign off on compliance — including the energy certificate and blower door documentation on new homes. Every project on this site, from a simple attic top-up to a gut rehab, should start with a conversation with the AHJ; a good installer coordinates this on rebated and permitted work.
Timeline at a glance
2008–2010: Legislature creates MUBEC; first statewide code takes effect. July 2021: 2015 editions in force. 2024: Board votes to adopt the 2021 I-codes and 2019 ASHRAE standards. April 7, 2025: the 2021-edition MUBEC — including the 2021 IECC and its R-60 attic / 3.0 ACH50 requirements — becomes enforceable statewide. Projects permitted since that date are reviewed under the new editions.
Building or renovating under the new code?
Our recommended installers insulate and air-seal to the 2021 MUBEC editions and document compliance for your code enforcement officer — R-values, air barrier details, and blower door results included.
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