We plan an ADU project in Longmont at 3–6 months from signed contract to move-in. Here is what happens in each phase, and what each one depends on.
This is the "kitchen table" phase. No commitment until you sign.
Longmont's ADU permit process is well-established. Pre-approved plan elements help. Typical review is 4–6 weeks; 8 weeks is conservative.
Panelized construction significantly compresses the framing phase. You get weekly photo updates throughout.
Longmont has one of the most straightforward ADU ordinances on the Front Range. Here's what makes it work:
ADUs in most residential zones are approved administratively — no public hearing, no neighbor notification, no planning commission. You apply, they review, you build.
500–800 SF by right, whatever the size of your house — larger only if the ADU stays within 50% of the home's finished, above-ground floor area. All accessory buildings together are capped at 75% of the home. 5' side and rear setbacks. No closer to the street than the house. No ambiguity.
Unlike some Colorado cities, Longmont does not require the property owner to live on-site. You can rent both the main house and the ADU.
Longmont does not require additional off-street parking for ADUs. One less thing to solve.
Most Longmont properties have sewer, water, and electric available at the lot line. Connection distances are typically short — reducing one of the biggest cost variables.
The building department has reviewed hundreds of ADU applications. They know what to look for and the process is predictable.
The property finder shows your lot, setbacks, and which plans fit — in 30 seconds.
Keep exploring
ADU rules by city
Cited, city-by-city ADU rules across the Front Range.
Questions answered
Allowed, how big, what it costs, how long — answered from the adopted codes.
How the finder works
What to type, what you get back, and what it deliberately will not tell you.
Rental income potential
Rent, resale value, and what a permitted second unit adds to your property.
ADUs for family
Aging parents, multigenerational living, childcare.
How to finance an ADU
HELOC, construction loans, and CHFA options.
Floor plans & pricing
Five plans, three finish grades, five architectural styles.
About Addwell
Who we are and how we build.