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LONGMONT SERVICES

Pop-Top Addition in Longmont

Licensed pop-top addition services for Longmont and Boulder County. Go up, not out — add a full second story.

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Pop-Top Addition

Go up, not out — add a full second story

Local Service

Pop-Top Addition Services in Longmont, Colorado

Autotelic provides professional pop-top addition services throughout Longmont and the surrounding Boulder County area. Pop-top second-story additions across the Denver metro — add bedrooms, bathrooms, and living space without expanding your footprint. Structural engineering included. Whether you're in Longmont (north Boulder County) or nearby communities, our team delivers quality workmanship backed by Colorado licensing and full insurance coverage.

Permit Thresholds

Longmont permit thresholds

Code reference
The City of Longmont has adopted the 2024 International Codes, including the International Residential Code, effective July 1, 2026.
Code reference
Retaining walls over 48 inches.
Code reference
Accessory buildings over 120 square feet.
Code reference
Accessory buildings 120 square feet or less in floor area, though it is recommended to secure them against wind damage, and they must still meet setback requirements.
Code reference
Fencing below certain heights (commonly 6 feet).
Foundations
For one-story accessory structures greater than 120 square feet, foundations must be designed by a Colorado-licensed engineer, and the drawings must be stamped and sealed by that engineer.
Code reference
The City of Longmont enforces the 2024 International Codes, which became effective on July 1, 2026, along with the Metro Cohort Model Code.
Code reference
The Longmont Municipal Code incorporates by reference the International Residential Code for One and Two-Family Dwellings, 2021 Edition, including various appendix chapters.

Codes are amended regularly — verify current requirements with **The City of Longmont Building Services (Building Inspection division) issues residential building permits.

Zoning & ADU

Longmont zoning & ADU quick facts

Code reference
The most common single-family residential districts that permit ADUs are Rural Residential (R-RU), Residential-Single Family (R-SF), and Residential-Mixed Neighborhood (R-MN).
Code reference
ADUs are permitted as an accessory use in the R-RU, R-SF, and R-MN zoning districts, among others.
Code reference
General ADU standards are found in Longmont Municipal Code (LMC) Sections 15.04.040 and 15.02.080.E.
Code reference
An ADU cannot exceed one-half (50%) of the finished, above-ground floor area of the main house.
Code reference
An ADU may total up to 800 square feet regardless of the principal dwelling's size.
Code reference
An ADU can be larger than 800 square feet if it does not exceed 50% of the finished, above-ground floor area of the principal dwelling.
Code reference
If an ADU is part of a garage structure, the combined area of the garage and habitable ADU space cannot exceed 800 square feet or 50% of the finished, above-ground floor area of the principal dwelling, whichever is greater.
Code reference
(LMC Sections 15.04.040.C.2 and 15.02.080.E.3)

Codes are amended regularly — verify current requirements with **The City of Longmont Building Services (Building Inspection division) issues residential building permits.

Energy Code

Longmont energy code quick facts

Code reference
2024 IECC (Metro Cohort Model Code based on the 2024 International Energy Conservation Code, with local/regional amendments), effective July 1, 2026.
Code reference
Longmont adopted the 2024 International Codes (including the energy code) along with the Metro Cohort Model Code (MCMC, based on the 2024 IECC with regionally aligned amendments) via Ordinance O-2026-29 (adopted ~June 9, 2026; see Municode Chapter 16.22 for the energy conservation code adoption).Ordinance O-2026-29
Code reference
This aligns with Colorado state requirements for jurisdictions updating codes around this period (must meet or exceed 2021 IECC + electric/solar-ready provisions, with amendments not reducing stringency).
Code reference
Longmont follows its policy of adopting each new IECC version; it is not the Denver Green Code or Energize Denver program.
Code reference
Longmont is in IECC Climate Zone 5B.
Key prescriptive requirements (from the adopted 2024 IECC/MCMC base provisions,
Key prescriptive requirements (from the adopted 2024 IECC/MCMC base provisions, applicable to additions and alterations per the IECC scope for new construction elements in remodels/additions) relevant to remodels/additions in CZ 5B include (specific MCMC amendments may modify details; always verify
Ceiling/attic insulation
R-49 (or equivalent U-factor per Table R402.1.2/R402.1.3).
Adopting ordinance/reference
MCMC/2024 IECC Table R402.1.2 (or R402.1.3 component performance alternative) as adopted in Longmont Municipal Code Chapter 16.22.
Ordinance O-2026-29Source: longmontcolorado.gov

Codes are amended regularly — verify current requirements with **The City of Longmont Building Services (Building Inspection division) issues residential building permits.

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What a pop-top covers

A pop-top in the Denver metro raises or replaces the roof on the existing footprint to add a story or habitable attic. Walls usually stay; massing and bulk plane control the envelope. The existing foundation still has to take the new loads. A municipally licensed Denver general contractor coordinates the project, design professionals, and licensed specialty trades. Cost is project-specific and depends on roof structure, stairs, and how much of the first floor is opened.

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Bulk plane, height, and landmarks

Zoning height is measured in feet and stories from the front and rear base planes (DZC Sec. 13.1.2). Plans must show allowed versus proposed bulk plane, including roof overhangs. If the existing house already breaks height or bulk rules, elevations should distinguish retained structure from new work. Landmark Preservation lists pop-top/rooftop additions as a review type; designated properties need Landmark approval before zoning or building permits.

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Permits and who coordinates the work

City and County of Denver Community Planning and Development treats pop-tops like other second-story or attic work: structural review and a sealed structural-integrity letter from a design professional who inspected the existing foundation (DBCA 133.3), plus zoning, building, and typically SUDP. Cities and counties license general contractors. Colorado has no statewide general contractor license. Autotelic acts as a municipally licensed Denver general contractor and coordinates licensed specialty trades plus the design professionals required for the project.

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What buyers should prepare

Target rooms, roof and attic photos, known foundation issues, and landmark or historic-district status.

FAQ

Common questions

Is a pop-top different from a second-story addition?

A pop-top usually stays on the existing footprint and is controlled by bulk plane. A second-story addition may also expand walls. Both need structural review in Denver.

Who handles pop-top permits and licensing?

A municipally licensed Denver general contractor coordinates the project, design professionals, and specialty trades. Colorado has no statewide general contractor license.

Do historic houses need extra review?

Yes. Landmark lists pop-top/rooftop additions. Approval comes before zoning and building permits on designated properties.

Will the existing foundation work?

Only after a design professional inspects it. CPD asks for a sealed structural-integrity letter for second-story and attic work.

What information helps define scope?

Desired rooms, roof photos, landmark status, and city or county.

Service Area

Serving Longmont and Boulder County

We serve Longmont, CO and all surrounding Denver metro communities. Our team is based in Denver and operates throughout the Front Range, from Castle Rock to Longmont and everywhere in between. Contact us for a free estimate on your Longmont project.

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