Private basement entrances for apartments & ADUs

A private basement entrance is a complete exterior and interior access project including

• Excavation beside the foundation
• Cutting a door opening into the concrete foundation wall and other interior layers
• Installation of a structural header
• Construction of stairwell or landing with retaining walls and drainage
• Setting the exterior door
• Interior and exterior finishing work

The goal is a separate, direct, external basement apartment entry. In Lehi, this is the key step that turns an ordinary finished basement into a true secondary living unit with its own front door.

You likely need a private basement entrance if

• You want to rent your basement as a long-term apartment, and tenants currently have to walk through your house.
• You are creating an internal accessory dwelling unit (ADU) or mother-in-law suite for parents or adult children who want their own door.
• Your basement has the bedrooms and a kitchen but no separate, code-legal way in and out.
• You want to separate your household from a basement unit for privacy, noise, or security.

A separate entrance is what makes a basement function as its own home rather than a shared downstairs.

Basement-apartment entrance construction in Lehi must take into consideration local laws and local conditions.

1. The law: Utah's HB 82 (2021), codified at Utah Code 10-9a-530, makes an internal ADU a permitted use in most residential zones, and Lehi's ordinance allows one ADU per qualifying parcel on a lot of at least 6,000 square feet, with owner-occupancy required and no short-term (under 30-day) rentals. A basement apartment created in an existing basement must have its own emergency escape-and-rescue opening under IRC R310.1.
2. The ground: Lehi's clay-heavy valley soil holds water and the March-to-May snowmelt drives moisture toward foundations, so a new entry stairwell must be built with proper drainage or it can flood. We design the entrance for both the law and the water.

Confirm current ADU rules with Lehi Planning at 385-201-1030 before you build.

We do not quote a price until we see your home due to the many factors specific to your site. These factors include:

• How deep your basement sits below grade (deeper means more excavation)
• Whether your foundation is poured concrete or block (poured concrete takes longer to cut)
• Your soil and how hard it is to dig
• The height of the retaining walls needed for the stairwell
• The door and any landing or patio you want
• The drainage system required to keep the stairwell dry
• Interior finishing (framing, drywall, trim, paint)
• City permit and engineering fees

For general context, we've seen basement entrances priced between $5,000 and $35,000 (averaging around $20,000). Every project is unique in some way, which is why we give a firm number only after a site visit.

Homeowners often ask whether they need a stairwell entrance or if their sloped lot can accommodate a walkout basement. If your lot is flat, the only option is to install a stairwell (areaway) entrance with a below-grade landing and steps up to the yard. Walkout basements require a sloped lot with the basement foundation at or near grade within a reasonable distance. We will confirm which one your lot supports and give the best result for your budget.