The Impossible Duplex Conversion

Duplex Conversion Case Study | Trueline Repair & Remodeling

Project Spotlight

The "Impossible" Duplex Conversion

How we turned a failing 1900s farmhouse into a high-revenue, code-compliant duplex rental.

1,800 sq ft Full Gut Remodel
Code Update Structural & Fire
Revenue +$3k/mo Income

The Starting Point: A 1900s Nightmare

When we walked in, this property was a disaster waiting to happen. Built in the early 1900s, it had been "added onto" four separate times by different people, resulting in a confusing layout and serious structural failures.

The heating system consisted of a single gas unit meant for a trailer—with no ductwork. The windows leaked air, the floors heaved, and one section of the home was heated by a pellet stove alone.

The Surprise Discovery: Behind the drywall, we found walls made of mud and straw bricks. One wall was failing so badly the roofline was sagging. We had to jack up the roof, remove the mud bricks, and reframe the entire exterior wall to modern 2x6 standards.

Demolition phase showing exposed framing Detail shot of structural issues

We stripped the interior down to the studs to correct structural failures hidden for decades.

Engineering the Split

Fire, Sound, and Separation

Converting a single-family home into a duplex isn't just about adding a door. It requires strict adherence to fire and safety codes.

The "Staggered Stud" Wall

To separate the two units (1,100 sq ft and 700 sq ft), we went above and beyond code. We built a staggered stud wall insulated with Rockwool. This design disconnects the drywall on one side from the studs on the other, significantly reducing sound transmission between tenants.

Fire Safety: We installed 5/8" Type X Fire-Rated drywall on both sides, used rockwool insulation, and built a "draft stop" in the attic to slow the spread of a fire. Safety was priority #1.

Demolition phase showing exposed framing Detail shot of structural issues

Framing the new separation wall required attention to details to meet fire code.

Smart Utilities & Safety

We removed the gas lines entirely, converting the home to a safer all-electric build. This eliminates the risk of carbon monoxide poisoning for future tenants.

  • Heating: Dedicated electric baseboard heat gives tenants room-by-room control.
  • Cooling: Roof-mounted evaporative coolers (swamp coolers) provide cost-effective cooling perfect for the dry Montrose climate.
  • Moisture Control: We wired the bathroom fans to the light switches. If the light is on, the fan is on. This prevents mold growth from tenants forgetting to vent the room.
New electrical rough-in

Updating the electrical to handle two modern units safely.

The Result: A High-Value Asset

The transformation was total. We installed new vinyl siding, new windows, and built a second kitchen from scratch. To ensure durability for a rental, we chose materials wisely:

  • Flooring: A mix of stained concrete (indestructible and cost-effective), tile in high-traffic wet areas, and easily replaceable carpet in bedrooms.
  • Fixtures: We used Delta faucets throughout—reliable, easy to service, and timeless design.
  • Baths: Single-piece bathtubs set on a mortar bed foundation to prevent cracking or movement.

Client ROI

The property now generates approx. $3,000 - $3,500/month in rental income. The equity increase was so significant that the owner was able to refinance, pull out cash to invest in a new property, and still maintain positive cash flow.

Project Gallery

Scroll to Top