Basement Finishing
Family rooms, guest suites, home offices and legal basement apartments
Make the most of the space you already have
An unfinished basement is often the most affordable square footage you can add to your home. We plan the space around how you’ll actually use it, handle the permits, and build it to code, from egress windows to insulation and moisture control.
Thinking about rental income or room for family? A finished basement can become a legal accessory dwelling unit (ADU). In Longmont, an ADU in an existing basement isn’t subject to the ADU size limit. Learn more on our ADU page.
St. Vrain Construction is a second-generation, licensed general contractor (Longmont license C01009653) serving Longmont, Boulder County and Weld County.
We get to you fast. We typically return calls the same or next business day, come out for an estimate within 3 business days, and get you a written estimate within 2 business days after that. Most projects start within 2 to 3 weeks of signing.
Basement work we do
🛋️ Living Space
- Family and rec rooms
- Home offices
- Guest bedrooms
- Home gyms
🛁 Baths & Kitchens
- Basement bathrooms
- Wet bars and kitchenettes
- Laundry rooms
- Basement apartments (ADUs)
🧱 Safety & Comfort
- Egress windows for bedrooms
- Framing and insulation
- Drywall, flooring and trim
- Lighting and outlets, wired by a licensed electrician
How a basement finish works with us
- We start with how you’ll use it. A place for the kids, a guest suite, an office, or a rental unit. That decides the layout, the bathroom, and whether you need egress windows.
- We talk honestly about budget. Knowing your budget lets us decide where to spend and where to save.
- We look for ways to get more for less. Placing a bathroom near existing plumbing, framing smartly around ductwork and mechanicals, and choosing durable, budget-friendly finishes.
- You get a clear, itemized estimate. Every room and line item is broken out so you can choose what to include now and what can wait.
- We handle permits and inspections. We pull the permits and schedule every inspection.
- We build it and walk it with you. Framing, rough-ins, insulation, drywall, flooring and finishes, followed by a final walkthrough.
What affects the cost of a basement finish
- Size and layout. More rooms and walls mean more framing, drywall and finishing.
- Bathrooms and kitchenettes. Plumbing below the main sewer line can require an ejector pump.
- Egress windows. Bedrooms need an emergency escape window, which can mean cutting the foundation.
- Moisture. Any water issues need to be fixed before finishing.
- Ductwork and ceiling height. Low beams and ducts take extra framing to work around.
- Finishes. Flooring, trim, doors and fixtures.
How long does it take? [Typical timeline for a basement finish]
Frequently asked questions
Usually quickly. We typically return calls the same or next business day, visit for an estimate within 3 business days, and send your written estimate within 2 business days after that. Most projects start within 2 to 3 weeks of signing, depending on materials and permits.
Yes. We pull the permits and schedule the inspections.
Yes. Building code requires an emergency escape opening in basement sleeping rooms, and we can install one.
Often, yes, as a legal ADU. See our ADU page for Longmont’s rules.
We take a 50% deposit to start, which covers materials. Larger jobs include a progress payment, and the balance is due when the work is done.
Ready to finish your basement?
Tell us how you want to use the space, and we’ll give you a clear, itemized estimate.
Or call (720) 310-0783