Detached Garage Conversion Project

Project Overview

At a Glance:

• Total Cost: $29,000-$34,000 (DIY) to $77,000-$82,000 (contractor approach)
• Timeline: 4-5 months (professional) or 6-12 months (DIY)
• Size: 884 sq. ft. finished interior space
• Layout: Open-concept living/kitchen area, two bedrooms, one bathroom, laundry nook
• Major Features: Modern minimalist finishes, luxury vinyl plank flooring, mini-split HVAC system

Financial Perspective:

• Monthly Rental Income: $1,200-$1,500 per month
• Annual Return: $14,400-$18,000 per year
• Investment Payoff: 2.0-5.7 years (depending on DIY vs. contractor costs)
• ROI: 18-50% annual return on investment
• Property Value Increase: Estimated 20-30% boost to overall property value
• Additional Benefits: Flexibility for multi-generational living, home office space, or short-term rental income
• Tax Considerations: Potential depreciation benefits and rental income tax implications (consult with a tax professional)

Existing Structure: A detached 36' x 28' concrete block (CMU) garage with a pitched roof. It currently has an overhead garage door at the front, a basic concrete slab floor (likely slightly sloped), plumbing rough-in for a bathroom, and a dedicated electrical sub-panel (amperage TBD). There is no gas service to the garage.

Conversion Goal: Transform this garage into a fully finished 2-bedroom, 1-bathroom residential unit (approximately 884 sq. ft. of finished interior space). This unit will function as an Accessory Dwelling Unit (ADU) – a self-contained living space with its own kitchen, bathroom, and sleeping areas, separate from the main house.

Major Challenges:

1. Permitting & Compliance: Rapid City limits ADUs to 800 sq. ft., but our plan is 884 sq. ft., requiring potential variance or design adjustment.
2. Garage Door Replacement: Converting the large garage door opening to a proper insulated residential wall with entry door and windows.
3. Floor Leveling: The existing concrete slab is sloped for drainage and requires building a raised, level subfloor system.
4. Window Installation: Installing proper egress-compliant windows in the existing CMU wall openings to meet code requirements and ensure weathertightness.
5. Climate Control: Designing adequate insulation and heating/cooling for Rapid City's extreme temperature ranges without gas service.
6. CMU Wall Repair: A damaged corner of the exterior CMU wall is warped/compromised (likely from vehicle impact) and requires structural repair before conversion.

Critical Design Elements:

• Open-Concept Living Area: A combined living room and kitchen for a spacious feel. The kitchen and bathroom will be positioned near existing plumbing lines to minimize new plumbing runs.
• Two Bedrooms: Each will comfortably fit a queen bed and have a closet. Both require code-compliant egress windows for safety and emergency exit.
• One Full Bathroom: Standard 3-piece bathroom (toilet, sink vanity, tub/shower) utilizing the existing plumbing rough-in.
• Laundry Nook: Space for a stacked washer/dryer unit near plumbing connections.
• Finishes & Fixtures: High-traffic luxury vinyl plank (LVP) flooring with a wood-look finish for durability and easy maintenance. Modern but mid-range cabinetry and fixtures will be installed throughout.
• Climate Comfort: The unit will feature robust insulation (R-13 to R-15 walls, R-38 to R-49 ceiling) and an efficient electric heat-pump mini-split system for heating and cooling.

In summary, this project represents a significant investment in property value, converting an underutilized garage into a comfortable, modern living space suitable for family members, rental income, or guest accommodations. The following sections provide a comprehensive breakdown of all construction tasks, detailed cost estimates, timeline expectations, permitting requirements, and recommendations for efficiency and durability.

Construction Scope and Tasks

1. Permitting and Design Planning

• Design and Drafting: Create a floor plan layout for the 2-bedroom unit, ensuring it meets building codes (e.g. room sizes, egress, window sizes, etc.). Professional drafting may be needed to submit with permits. (Consider hiring a residential designer or architect for plans; some ADU projects budget ~$5,000 for professional design , though simple projects can use contractor-drawn plans.)
• Zoning Check: Confirm that an ADU is allowed on the property. Rapid City's ADU ordinance permits such units in residential zones, but typically limits ADU size to 800 sq ft in SD's definition . (At ~884 sq ft, a minor variance or exception might be required, or the design may be adjusted to comply with the 800 sq ft limit. This should be clarified with the city planning department.)
• Permit Applications: Prepare and submit a building permit application with construction plans to the Rapid City Building Services Division. Because this is a change of use (garage to dwelling), the plans must show compliance with residential codes (framing, egress, insulation, electrical, plumbing, HVAC, etc.). Multiple permits will likely be needed (or one building permit that encompasses sub-trades):
  • Building Permit – for structural changes, insulation, drywall, general construction.
  • Electrical Permit – for wiring, panel changes, and fixtures.
  • Plumbing Permit – for supply, drain, waste, vent lines, and fixtures installation.
  • Mechanical Permit – for HVAC installation (if adding a mini-split or other heating/cooling).
• ADU Registration: Complete Rapid City's ADU registration form (required since the city enacted an ADU ordinance). This typically involves a small fee and documentation to officially register the unit as an ADU with the city  .
• Historic Review (if applicable): If the property is in a historic district or older neighborhood, an additional review may be needed for exterior changes. (This may not apply, but worth checking given the address.)
• Planning for Utilities: Coordinate with utility companies if upgrades are needed (for example, ensuring the water supply line and sewer connection can handle an additional dwelling, and checking if the electrical service to the garage needs upgrading).

Estimated Permit Costs: In Rapid City, permit fees are generally based on project value. For a project of this scope, expect a few hundred up to around $1,000+ in total permit fees. (Nationally, building permit costs for garage conversions average about $1,350, and can range $1,500–$3,000 in more complex cases . Rapid City's fees are likely on the lower end of that range, but budgeting around $500–$1,000 for all permits and inspections is prudent.)

2. Site Preparation and Demolition

• Clear-Out and Prep: Remove any stored items and non-structural elements from the garage. If the walls have interior finishes (unlikely in a bare garage), remove drywall or paneling to expose the block and framing.
• Garage Door Removal: Carefully remove the large garage door and its hardware. This leaves a large opening to be filled in with a new wall structure.
• Concrete Slab Evaluation: Check the slab for cracks or elevation changes. Garage slabs are often slightly sloped toward the door for drainage – this will need to be addressed when creating the level interior floor (see next section). If any trenching or slab cutting is needed for new plumbing lines (e.g. for a kitchen drain or relocating the bathroom layout), do this now:
  • Excavate and cut the concrete where new underground plumbing or electrical conduit is required. (For example, running a new drain line for the kitchen sink to tie into the existing bathroom drain might require opening a trench in the slab, unless an above-floor plumbing solution is used with the new subfloor.)
• Old Fixtures and Utilities: If any existing light fixtures, old plumbing pipes, or wiring will be in the way of new construction, remove or relocate them at this stage. Shut off power to circuits in the garage before demolition of electrical components. Cap any old plumbing lines temporarily if needed.
• Site Grading Check: Verify drainage around the garage. Since it will become living space, it's important the ground slopes away from the foundation. Plan for improvements if water tends to pool near the slab – e.g. regrading or adding gutter downspout extensions – to keep the interior dry long-term.

3. Foundation and Floor Construction

• New Footing (if required): Once the garage door is removed, the opening at the front will be filled with a framed wall (with a door/window). If the existing slab edge at that opening has no frost footing (many garages have a thickened slab edge or minimal footing under door opening), you may need to pour a concrete footing or curb below the new wall for support and code compliance. This involves digging a trench at the opening, tying into existing slab edges, and pouring concrete to the required depth (local frost line in Rapid City is around 32–36 inches). An alternative allowed by code could be a frost-protected shallow foundation using rigid foam insulation around the perimeter, but this should be designed per code. Consult the building inspector to see if the existing condition is acceptable or a new footing is needed for the converted exterior wall.
• Raise and Level the Floor: Build a raised subfloor over the existing slab:
  • Install a moisture barrier (plastic sheeting) on the slab to prevent vapor transfer.
  • Attach pressure-treated sill plates around the perimeter where interior framing will sit on the slab.
  • Frame a grid of floor joists or sleepers (e.g. 2x4 or 2x6 lumber) across the slab to create a level floor. These can be shimmed to account for any slab slope so that the top is perfectly level. Joist spacing 16" on-center is typical.
  • Insulate between joists with rigid foam or batt insulation. This will keep the floor warmer in winter – important since concrete slabs can be very cold. (E.g. R-13 to R-19 insulation in the floor cavity if using 2x4 or 2x6 framing.)
  • Install subfloor sheathing (3/4" plywood or OSB) on top of the joists. Glue and screw it down for a solid, squeak-free floor.
• Repair/Fill Concrete Cuts: If any trenches were cut for plumbing, backfill them with gravel and patch the concrete (or fill with gravel and cover with the new subfloor above, as long as structurally sound). Ensure any penetrations through the slab for plumbing are sealed or tight to prevent pest entry.

4. Structural Modifications and Framing

• CMU Wall Repair: Before proceeding with additional framing, the damaged corner of the exterior CMU wall must be repaired. This involves removing compromised blocks, installing new reinforcement if needed, and rebuilding the corner with matching CMU blocks. Depending on the extent of damage, this may require temporary bracing during repair. The repair should be completed by someone experienced with masonry structural work to ensure the wall's integrity is fully restored before interior finishing begins.
• Infill Front Wall: Frame a new exterior wall in the former garage door opening:
  • Use 2x6 or 2x4 studs (2x6 allows more insulation depth, recommended for external walls in this climate). Anchor the bottom plate to the slab/footing and tie the top plate into the existing header or ceiling framing. If the garage door header is too low and you have height to spare, you might remove it and reframe that section for a full-height wall.
  • Frame in the rough opening for a new exterior entry door (typically 36" wide) and possibly additional window(s) as desired for light in the living room. Ensure proper headers above the door/window per structural requirements.
  • Sheathe the exterior of this new wall with plywood/OSB, and weatherproof it (housewrap or felt).
• Window Installation in Existing CMU Openings:
  • The garage already has window openings in the CMU walls that will be utilized for the new living space.
  • Frame the rough window openings with pressure-treated lumber attached to the block (fastened with anchor bolts or masonry screws). This provides a surface to mount the new windows.
  • Ensure openings for bedroom windows meet egress requirements (minimum net clear opening of 5.7 sq. ft., with minimum height of 24" and width of 20"). If any existing openings are too small for egress, they may need to be enlarged.
  • Install the new vinyl windows in these openings, shim and level them, and seal the perimeter with spray foam and flashing tape on the exterior for water tightness.
• Interior Partition Walls: Frame the new interior walls for the two bedrooms, the bathroom, and any closets:
  • Use 2x4 lumber for interior partitions. Standard practice is 16" on-center stud spacing.
  • Include headers above interior door openings and install horizontal blocking where things like wall-mounted cabinets or heavy shelving might go.
  • Bedrooms: likely will be along one side or at the back – ensure each has a door and a closet framed in. Bedroom walls should run all the way up to the ceiling framing.
  • Bathroom: Frame walls to enclose the bathroom. If space is tight, consider pocket doors (framed with a pocket door kit) to save room. Ensure enough width for fixtures (minimum ~5' for a bathroom to fit a tub along one wall).
  • Laundry Nook: Frame a closet or niche for the stacked washer/dryer. Include backing for dryer vent installation and an access panel if needed for plumbing.
• Ceiling and Attic: Determine ceiling approach:
  • If the garage has open rafters or a truss roof, you'll likely install a flat ceiling at ~8' or higher. Frame a ceiling by adding ceiling joists or using the bottom chords of trusses if present. This creates an attic space above for insulation.
  • Provide an attic access hatch (required by code for service, usually 22"x30" opening minimum).
  • Ensure the roof structure is sound. If any upgrades are needed (e.g. hurricane ties, rafter reinforcing) have those done now.
• Blocking and Backing: Install any extra blocking in walls for things like wall-mounted TV brackets, bathroom grab bars (if planning for aging-in-place), towel bars, etc., to ensure they have solid anchorage.
• Exterior Work (Concurrent): As framing is completed, also:
  • Install the new exterior entry door (pre-hung unit). Include proper flashing around it and a threshold pan if possible to prevent water ingress.
  • Frame and attach any exterior stairs or landing if the new door is elevated due to the raised floor. (Likely a single step or small landing outside the door will be needed to meet code for egress; any platform over 30" high would need a railing by code, but a 6"–8" step usually doesn't.)
  • Begin exterior finishing on the new wall section: for example, install siding or exterior veneer to match the house or a complementary material. If the existing garage exterior is bare block, a common approach is to stucco over the block or paint it. The new framed wall could be covered with fiber-cement siding panels or stucco to blend in. We'll detail finishes later, but at this stage ensure it is weather-tight (sheathing and housewrap in place).

5. Utility Rough-Ins (Plumbing, Electrical, HVAC)

This phase involves all the behind-the-walls mechanical work, which will later be inspected before closing up the walls. It's often done by licensed subcontractors. Coordination is key so they don't conflict (e.g. plumbing and electrical trying to use the same wall space).

• Plumbing Rough-In:
• Drain-Waste-Vent (DWV): Using the existing bathroom plumbing stub as a starting point, layout and install all drain lines:
• Connect the toilet, shower/tub, and sink drains in the bathroom to the main sewer stub (likely there is a 3" or 4" waste line from the garage floor that ties to the sewer). Vent these through the roof (a vent stack pipe will run vertically from the bathroom up through the roof to allow sewer gases to escape and assure proper drainage).
• For the kitchen, run a 2" drain line from the sink location to tie into the existing sewer line (this might run through the wall and join the main drain under the slab or at an accessible point). The kitchen sink will also need a vent (which can often tie into the bathroom vent if nearby, or use an AAV air-admittance valve if allowed by local code).
• Laundry drain: a standpipe and trap for the washer, typically 2" drain tying into the system (possibly joining the kitchen or bath line if close, or directly into the main).
• Water Supply Lines: Run hot and cold PEX or copper pipes to all fixtures:
• Likely tie into the main house water supply line or a dedicated line if one was run to the garage. Ensure a separate shutoff valve for the ADU's water supply.
• Cold water and hot water lines to the bathroom (sink, toilet (cold only), shower). Lines to the kitchen sink (and dishwasher), and to the laundry washer hookup.
• Install a water heater. Since no gas line exists, an electric water heater is planned (e.g. a 40-gallon electric tank). Frame a small water heater closet or use part of the laundry area or bathroom for it. It will need a 240V circuit. Alternatively, a tankless electric could save space but might require a very high amp draw – likely stick to a tank for simplicity.
• Don't forget a pressure relief valve line from the water heater (often run to the exterior or a drain).
• Exterior Hose Bibb: Optionally, install an exterior faucet on the garage for convenience, tying off the cold line (with a frost-proof sillcock type faucet).
• Once all pipes are run, cap lines and perform a plumbing pressure test (air or water) for inspections. Also test DWV with water or air (inspectors may require a water or air test to ensure no leaks).
• Electrical Rough-In:
• Power Supply and Panel: Evaluate the existing sub-panel in the garage. It must support the new loads:
• If the existing feed is, say, 60 Amp and the new unit will have an electric range, water heater, and heat/AC, this may be insufficient. Consider upgrading to a 100 Amp sub-panel feed from the main house, or even a separate service meter if needed (though separate meter likely not required if ADU is accessory).
• Upgrading may involve running new underground cable or overhead wire from the main service to the garage and installing a new breaker in the main panel. Consult a licensed electrician for load calculations.
• Circuit Wiring: Install wiring per code (Romex NM cable or in conduit if required):
• Kitchen: At least two 20-amp small-appliance circuits for countertop outlets, a dedicated circuit for the fridge (often 20A), a 240V 50A circuit for an electric range, and possibly a dedicated circuit for a microwave if it's a large one or a range hood combo.
• Laundry: dedicated 30A 240V circuit for an electric dryer (if using electric dryer), plus a 20A circuit for the washer (or this can share with general).
• HVAC: a 240V circuit for the mini-split heat pump (or 120V if using a smaller unit or baseboard heaters – but likely a 20A or 30A 240V for a 12,000-18,000 BTU heat pump).
• Water heater: dedicated 240V (likely 30A) circuit.
• Lighting and general outlets: Typically one or two 15A or 20A circuits for lighting, and 15A or 20A circuits for general outlets in rooms. Bedrooms and living area outlets must be on arc-fault protected circuits (AFCI breakers or combo devices) per code.
• Bathroom: 20A circuit for bathroom outlets (must be GFCI protected) – can be shared with lighting in bathroom or separate.
• Outlets & Switches: Rough-in all electrical boxes:
• Place outlets along walls to meet code spacing (no more than 12 feet apart, and an outlet on any wall 2 feet or wider).
• Special boxes for stove, dryer, etc. as needed.
• Switch boxes for lights (e.g. switches for overhead lights in each room, for exterior light at entry, for bathroom fan/light, etc.).
• Wiring for smoke detectors: Hard-wired smoke alarms with battery backup must be installed in each bedroom and in the hallway/common area (and usually interconnected). Since this is a separate unit, these can be on its own circuit or tied to a lighting circuit (but must be interconnected within the unit).
• Include a carbon monoxide detector in the unit per code (usually required outside sleeping areas in dwelling units, even if all-electric, for safety).
• Rough-in for any low-voltage or cable needs (Internet, TV coax) if desired.
• After running all cables and before installing devices, call for electrical rough-in inspection. The inspector will check that wire size, anchoring, box fill, etc., are correct.
• HVAC Installation:
• Heating/Cooling Solution: Given no gas, an electric heat pump is ideal for efficiency. Plan for a mini-split system:
• Likely a single-zone ductless mini-split with one wall-mounted indoor unit in the living area could heat/cool the open living/kitchen and some air will flow to bedrooms. However, to ensure bedrooms stay warm, you may add electric baseboard heaters in bedrooms or use a multi-zone mini-split (with two or three indoor units). For simplicity, one 18,000 BTU mini-split head in the living area plus perhaps 1-2 baseboard heaters as backup is a cost-effective approach.
• Installation: Mount the mini-split's interior air handler high on an exterior wall (for example, in the living area). Install the exterior condenser on a slab or wall bracket outside. Drill through wall for refrigerant lines and wiring. (This is typically done by a qualified HVAC technician. DIY-minded owners sometimes install pre-charged DIY mini-split kits to save cost.)
• Run the needed electrical circuit to the condenser unit disconnect.
• If using baseboards, rough-in those on exterior walls and run their wiring from the panel (thermostats for each).
• Ventilation: Install a bathroom exhaust fan vented to the outside (through roof or sidewall). This is crucial for moisture control. Also, plan a kitchen range hood that vents outside (recommended for full kitchens). If a dedicated range hood isn't in plans, an OTR (over-the-range) microwave with exhaust or a recirculating hood can be used, but external venting is better for smoke/odor.
• Dryer Vent: If using a vented dryer, install a 4" dryer exhaust vent through an exterior wall, with a backdraft damper and hood.
• Ensure adequate attic ventilation if you created an attic space (install soffit vents and roof or gable vents, or use a ridge vent, to prevent moisture buildup in attic insulation).
• Consider an ERV/HRV (energy recovery ventilator) for fresh air if the unit will be very tightly insulated – though not typically required for such a small unit, it's an optional efficiency upgrade.
• Utilities Coordination: At rough-in stage, inspectors will check plumbing, electrical, and mechanical rough installations. Ensure all trades coordinate so, for example, a plumbing vent isn't placed where the electrical needs to run, etc. After rough inspections pass, you can proceed to insulation and closing up walls.

6. Insulation and Building Envelope

• Wall Insulation: Now that rough wiring/plumbing is in, insulate all exterior walls. For block walls, you have a few options:
• If you framed furred walls inside the CMU (e.g. 2x4 framing along the interior side of block), fill those stud cavities with batt insulation (e.g. R-13 fiberglass or higher density R-15). Use faced batts (vapor barrier facing inside) or unfaced batts with a separate vapor retarder if required by local code. In a cold climate like Rapid City, a vapor retarder on the warm side is often recommended.
• Alternatively or additionally, some choose to attach rigid foam insulation directly to the interior of the block (e.g. 2" XPS for ~R-10) and then frame a wall inside that. If that approach was taken, it should be done prior to running electrical (since foam would sit behind the studs).
• Ensure corners and narrow spaces are also insulated – cut pieces to fit as needed.
• Ceiling Insulation: insulate the ceiling to meet code (typically R-38 to R-49 for attics in this climate). The easiest method is blown-in insulation (fiberglass or cellulose) in the attic after drywall is up, but if doing before drywall you could staple batts between ceiling joists. Blown cellulose to ~R-40 (about 12-14 inches) is cost-effective and can be done after the drywall is installed (with an attic access).
• Don't forget to baffle around soffit vents and keep vents unblocked if using blown insulation, and to insulate the attic hatch or use an insulated cover for it.
• Floor Insulation: If not already insulated during subfloor construction, ensure any gaps around the floor framing are sealed. If there's space at the rim or edges, spray foam or caulk to seal out drafts.
• Windows and Doors Sealing: Foam around window and door frames (low-expansion foam around windows to avoid bowing the frames). Check that all exterior penetrations (wires, pipes, vents) are sealed with caulk or foam.
• Sound Insulation (interior): As an optional step, you can add insulation into interior walls for soundproofing (e.g. around bathroom or between bedrooms and living area). This could be inexpensive fiberglass batts for noise dampening.
• Inspection: The city may require an insulation inspection or energy code inspection at this stage, to verify R-values and installation before covering. Ensure all insulation is in place and any required air/vapor barriers are correctly installed.

7. Drywall and Interior Finishes

• Drywall Hanging: Hang drywall (sheetrock) on all framed walls and ceilings:
• Ceilings typically use 5/8" thick drywall (for better sag resistance, especially if trusses at 24" spacing, and it also provides a 1-hour fire rating separation from attic which might be code if garage was detached – though for an ADU it's not a garage anymore, fire separation is not the same concern).
• Walls can use 1/2" drywall. In the bathroom, use moisture-resistant drywall ("greenboard" or similar) on walls or cement backer board in wet areas (surround of a tiled shower, if you tile). If using a fiberglass tub/shower unit, regular drywall above it is fine but greenboard is a plus.
• Apply drywall to both sides of all interior walls (bedroom walls, etc.), and around any soffits or chases built for utilities.
• Taping and Mudding: Finish the drywall seams and screw holes with joint tape and compound. This is typically a 3-coat process (tape coat, fill coat, finish coat) with sanding in between. It can take several days to a week to complete due to drying time.
• If DIY, be meticulous to get a smooth finish. If hiring, a crew might do this in 2-5 days depending on methods (some use quick-set muds).
• Texturing (optional): Depending on preference, apply a texture to the walls/ceiling (e.g. a light knock-down texture or orange peel) or leave smooth. Texture can help hide minor imperfections and is common in many areas.
• Primer and Paint: Once drywall is finished and sanded, apply primer to all surfaces. Then paint the interior:
• Ceilings typically flat white paint.
• Walls with a durable washable paint (eggshell or satin finish) in the desired color palette (likely light neutral colors to make space feel larger).
• Apply at least two coats for even coverage. Don't forget to paint trim separately (or later) if it's paint-grade.
• Interior Doors: Install the 5–6 new interior doors:
• Pre-hung hollow-core or solid-core doors on bedrooms, bathroom, and possibly a door to close off the laundry nook (or use bi-fold/slide doors for closets, etc.).
• Shim and hang doors plumb, install door casing trim around them.
• Attach door hardware (handles, privacy locks on bathroom and bedroom doors).
• Interior Trim: Install baseboard trim along all finished floors/walls, and trim around windows and doors:
• A simple ranch or colonial casing (per the minimalist design) in paint-grade wood or MDF would suffice. Caulk and fill nail holes, then paint the trim.
• Ensure window sills and aprons are installed as needed (unless windows are flush mount that don't require interior wood sills).
• Flooring: After painting (to avoid paint on new floors), install the finish flooring:
• Luxury Vinyl Plank (LVP) flooring throughout the living room, kitchen, hallway, and bedrooms as specified for durability. This material is typically click-lock or glue-down planks that resemble wood. It is waterproof – good for kitchen and potentially bath too.
• If a different finish is preferred in the bathroom (e.g. tile floor), install cement board underlayment in the bathroom and lay ceramic tile flooring, or continue the LVP for simplicity (many LVP products are suitable for bathroom use and provide a seamless look).
• For a raised floor, ensure the transition at the entry door is properly weatherstripped and there's a solid threshold piece.
• Install matching transition strips or thresholds at doorways as needed (e.g. bathroom tile to LVP).
• Cabinetry and Countertops: Install kitchen cabinets and bathroom vanity:
• The kitchen likely has a modest layout (perhaps an L-shape or one wall of cabinets since space is limited). Secure base cabinets to the floor and wall, and uppers to the wall studs. Ensure proper alignment and level.
• Install a durable countertop (laminate for budget or a higher-end like quartz if desired – but laminate or butcher block fits the "modern but not high-end" spec).
• Cut out for the sink in the countertop and drop in the kitchen sink (but wait to connect plumbing until fixtures stage).
• Install the bathroom vanity cabinet and top. If using a standalone sink, secure it accordingly.
• Add any storage cabinets or shelving (e.g. a linen closet cabinet or shelving in bath if needed).
• Tile and Bath Surround: If the bathroom will have tiled tub/shower walls instead of a prefab unit, this is the time to waterproof (with backer board and membrane) and install tile. However, a prefabricated tub/shower unit is more cost-effective and easier – in that case, it should have been installed during framing or rough plumbing stage. Assuming a prefab fiberglass shower/tub was installed (often done before drywall to attach to studs), then now just finish the drywall edge around it and plan for trim if needed.
• Closets: Add rod and shelf hardware in closets, and install closet doors (sliding or bifold doors, or if walk-in closet, a swing door).

8. Fixtures Installation and Final Utilities Hookups

• Plumbing Fixtures:
• Set the toilet in the bathroom (on a properly sealed wax ring, bolt it down).
• Install the shower/tub fixtures (showerhead, tub spout, faucet handles – the mixing valve should have been installed during rough plumbing; now attach trim kit).
• Install the bathroom sink faucet and connect water lines and drain (P-trap) to the wall stub-out.
• Install kitchen sink faucet and connect plumbing. Hook up the dishwasher drain and supply if a dishwasher is included (likely a small 18" unit could fit if desired).
• Connect the water heater: attach cold water inlet and hot water outlet, and run the temperature-pressure relief (TPR) valve line down to a safe discharge point. Turn on power to it after filling.
• Set up washer hookup: install the washing machine valves and drain connection. Later, the washer will just be connected to these.
• After all fixtures are in, turn on water and check for leaks. Also test the drainage by running water in sinks, shower, flushing toilet, etc.
• Electrical Fixtures and Devices:
• Install all the receptacles (outlet plugs) and switches into their boxes with cover plates.
• Install light fixtures and fans:
• Ceiling lights in bedrooms (could be simple LED dome lights or ceiling fan/light combos if desired for air circulation).
• Living area lights (maybe surface-mounted fixtures or track lighting if style calls, or floor lamps on switched outlets if that was planned).
• Kitchen light and any under-cabinet lights if included. Also install the range hood or OTR microwave and wire it up.
• Bathroom: vanity light above mirror, and ensure the exhaust fan is wired and has its cover installed.
• Exterior: mount an exterior light at the entry door (and any back/side door if exists). Also possibly motion lights on the exterior for security.
• Install smoke/CO detectors and verify they are interconnected and functioning.
• If any electric baseboard heaters or thermostats were part of HVAC, hook those up now.
• Label the electrical panel breakers properly for the new circuits.
• HVAC Final Steps:
• For a mini-split, the indoor unit and outdoor unit should be connected and the refrigerant lines vacuumed and tested by a technician. Then test the system for heating and cooling. Set up the thermostat controls (some mini-splits use a remote).
• Test any baseboard heaters or other supplementary heat.
• Test the bathroom vent fan and range hood for proper airflow to outside.
• Appliances:
• Move in and install appliances: refrigerator, range/oven, microwave, dishwasher, washer, dryer.
• The electric range and dryer will need their 240V cords plugged in and secured. The washer and fridge just plug into outlets.
• Test all appliances.
• Exterior Finishes & Touch-ups:
• Complete the exterior wall finish at the old garage door area: for example, if using siding, install the siding, corner trim, caulk seams, and paint as needed. If stucco, complete the final coats to blend with existing.
• Install any missing exterior trim around new windows (and caulk edges) and paint the trim or the block wall to create a uniform look. A fresh coat of paint on the entire exterior (or at least the converted wall and touched-up areas) will improve appearance and durability.
• Ensure the roof is flashed properly around new vent penetrations (plumbing vents, exhausts). Patch and seal any roof penetrations made.
• Reattach or install gutters on the roof edge if not already to direct rain away from the foundation.
• Install the house numbers on the ADU's exterior if required for identification and any final site work (like a stepping stone path or small concrete pad outside the entry).
• Final Inspection and Certificate of Occupancy:
• After everything is complete, schedule the final inspections for building, electrical, plumbing, and HVAC. The inspectors will verify that all work meets code. They will check things like GFCI outlets in kitchen/bath, proper egress windows, smoke detectors, stair/step safety, etc.
• Once approved, the city will issue a Certificate of Occupancy for the new residential unit, legally allowing it to be inhabited.

Each of these tasks will involve materials and labor. Next, we break down the estimated costs for each major phase or component of the project, with "low" and "high" estimates to reflect DIY savings vs. hiring contractors.

Cost Estimates (Itemized)

Below is an itemized cost breakdown for the conversion. We provide a low-range estimate (assuming the owner does portions of the work DIY or sources affordable materials) and a high-range estimate (assuming most work is hired out to contractors at market rates and using mid-grade materials). These estimates are rough 2025 prices and actual costs can vary. All values are in USD.

Explanation of Estimates: This budget-friendly version makes strategic compromises on finishes and fixtures while maintaining quality on structural elements and code compliance. Key cost-saving strategies include:

1. Using RTA (ready-to-assemble) cabinets and laminate countertops instead of pre-assembled or higher-end surfaces
2. Choosing basic/budget appliances, possibly sourced from outlet stores or gently used
3. Installing economy-grade LVP flooring ($1-2/sq ft vs. $3-4/sq ft)
4. Simplifying electrical plans with basic fixtures and fewer recessed lights
5. Using a DIY mini-split kit with pre-charged lines rather than a professional multi-zone system
6. Selecting hollow core doors and simpler trim profiles
7. Opting for simplified drywall textures and basic finishes
8. Choosing budget-friendly windows while ensuring they meet egress requirements
9. Using more cost-effective exterior finishes and simpler design elements

These adjustments reduce costs significantly without compromising the core functionality or livability of the space. The CMU corner repair and other structural elements remain properly budgeted as these are essential for the integrity and safety of the conversion.

Timeline for Completion

The project timeline can vary significantly based on whether the owner is DIY-ing or hiring a contractor, and on factors like weather, permitting time, and subcontractor scheduling. Below is an estimated timeline for this conversion:

• Design & Permitting: Approximately 2–5 weeks. This includes drafting plans and city review time. In Rapid City, small project permits might be obtained in a few weeks if plans are straightforward, but allow extra time for any revisions the city might require (especially because it's a change of use to an ADU).
• Initial Site Work and Demo: 1 week. Removing the garage door, clearing the space, and any slab trenching can be done in a few days to a week.
• Structural Framing & Exterior: 2–3 weeks. This covers building the new front wall, cutting in windows, framing interior walls, and any needed structural work. Concurrently, the new subfloor and any footing work would be done here. (Much of this could go faster with a skilled crew – possibly in one week – but DIY may stretch it to several weekends.)
• Utility Rough-Ins: 3–4 weeks. Plumbing, electrical, and HVAC rough-in might take roughly a week each if done sequentially (with some overlap). Inspections are needed after each, which can add a few days scheduling. So allow about a month for all utilities roughed in and inspected.
• Insulation & Drywall: 2–3 weeks. Insulating is quick (a day or two), but drywall hanging, mudding, and drying times take up to 1–2 weeks. If a drywall crew is hired, they might finish in 1 week. DIY could take longer. Include inspection of insulation if required before drywall.
• Interior Finishes: 3–5 weeks. This phase includes installing flooring, trimming out, painting, cabinets, fixtures, etc. A contractor might do this in 2–3 weeks with various subs (painting 2-3 days, flooring 2 days, trim 2 days, cabinets 1-2 days, fixture installs 2 days, etc., some in parallel). DIY on nights/weekends could stretch this to a month or more.
• Final Wrap-Up: 1 week. Final adjustments, touch-up paint, hooking up appliances, cleaning the site, and scheduling final inspections. Inspections might not align perfectly, so there could be a little waiting.

In summary, a professional contractor team might complete this entire conversion in roughly 3 to 4 months of work time. Given some buffer for permit timing and any delays, 4–5 months is a fair estimate for a fully contracted job of this scale. On the other hand, a part-time DIY approach (where the owner works on weekends and maybe hires out only critical parts) could take on the order of 6 months up to a year to complete, depending on how consistently work progresses. It's not unusual for DIY renovations to extend due to the owner's available time.

Seasonal Considerations: In Rapid City, starting construction in spring or summer is ideal so that any exterior work (cutting openings, pouring a footing, etc.) can be done in good weather. The bulk of work is interior, which can proceed year-round (with temporary heat in winter if needed). Plan the timeline such that the structure can be closed up (windows/doors in) before the colder months to allow interior finishing in a climate-controlled space.

Permitting and Inspection Considerations (Rapid City, SD)

Converting a garage to a living unit involves several legal and safety considerations. Below are notes on permits and inspections likely required in Rapid City:

• Building Permit: Required for the change of use and construction. The city will examine plans for compliance with the International Residential Code (IRC) as adopted by South Dakota and local amendments. Expect to submit floor plans, wall details, insulation specs (to meet energy code), window and door specs (for egress and safety glazing where needed), etc.
• Trade Permits: Separate permits (or combined under a general permit if a GC pulls them) for:
• Electrical (upgrading panel, new wiring) – electrical work must generally be done or overseen by a licensed electrician.
• Plumbing (new DWV and water lines, fixtures) – to be done by a licensed plumber or the homeowner if allowed under a homeowner's permit (jurisdictions vary on whether homeowners can do their own plumbing/electrical – Rapid City might allow it for owner-occupied property, but confirm).
• Mechanical/HVAC (installing a mini-split and any ducting or ventilation).
• Accessory Dwelling Unit (ADU) Regulations: Rapid City's municipal code for ADUs (Section 17.50.219) sets certain requirements:
• Only one ADU per lot, and it must be on the same lot as a primary dwelling.
• It must provide the basic facilities for living – which this project does (kitchen, bath, sleeping space) .
• Size limit: As noted, ADUs in SD are defined as 800 sq ft or less . If the design exceeds this, discuss with Planning – sometimes a slight exceedance might be permissible based on structure footprint, or the city might treat it as a duplex unit if zoning allows. Most likely, you'll need to adhere to that size cap for it to qualify formally as an ADU.
• Parking: Some cities require an extra off-street parking space for an ADU, especially if you converted a garage that provided parking. Check Rapid City's requirements. If so, you might need to show a driveway space or pad for parking.
• Owner Occupancy: Verify if Rapid City requires the property owner to live in either the main house or the ADU (common in some ADU ordinances to prevent both units being rented out).
• Addressing: The ADU may need a distinguishable address or unit number (for emergency 911 purposes). The city or county will advise on how to label the unit.
• Inspections: Throughout construction, expect several inspection visits:

1. Footing/Foundation Inspection: If a new footing is poured, inspector checks depth/rebar before pouring concrete.
2. Framing Inspection: After structural framing (and before insulation/drywall), to verify proper construction, window installation, headers, etc. Often done in conjunction with rough-in inspections.
3. Rough-In Inspections: Separate inspections for electrical, plumbing, and mechanical rough-ins. The inspectors will verify everything is to code (e.g. proper wire gauge, plumbing slopes and venting, duct sizes, etc.).
4. Insulation Inspection: Many jurisdictions do an insulation or "energy" inspection to ensure the proper R-value insulation is installed and things like windows and door ratings meet energy code.
5. Drywall nailing (optional): Sometimes the framing inspection covers this, but if any drywall is part of a fire barrier requirement, they might inspect screw spacing before taping.
6. Final Inspection: At completion, the inspector(s) check that all finish work complies: GFCI outlets are in place, appliances functional, safety devices (smoke/CO alarms) installed, windows operate (and egress window well depth if needed), handrails/guards present where required, etc. After passing, a Certificate of Occupancy is issued for the new dwelling.

• Utilities and Impact: Because this is an ADU on an existing property:
• Electrical: If sharing the main house's electrical service, ensure the main panel can handle the additional load. Otherwise, utility might need to upgrade the service drop or transformer. No separate power meter is required unless desired.
• Water/Sewer: It will tie into existing lines. If the property is on city sewer/water, typically you won't need to pay separate connection fees since it's existing, but check if any impact fees apply for creating a new dwelling unit. (The permit office can clarify if any additional costs for utilities or system development fees are relevant.)
• Egress & Safety: By code, each bedroom needs one egress window (net clear opening 5.7 sq.ft., min height 24", width 20"). The new windows should be chosen to meet these dimensions . Smoke alarms must be hard-wired and interconnected. If any fuel-burning appliance was present (it's not, since no gas, but if later adding a fireplace or such), CO alarms required.
• Fire Separation: Since the ADU is detached, fire separation from the main house isn't an issue like it would be if attached. But ensure any walls close to property line meet fire-rating if applicable (likely not an issue on this lot).
• Final Documentation: Complete any required registration (the ADU registration with the city) and update property records. The ADU will be officially noted, which is important for future resale or rental.

Being diligent with permits ensures the project is legal and safe – unpermitted work can lead to issues down the road (and Rapid City, like most cities, will require all these conversions to be permitted and the ADU to be registered to be occupied legally).

Recommendations and Considerations

Finally, here are some optional recommendations to enhance the project's outcome in terms of energy efficiency, layout optimization, and long-term durability:

Energy Efficiency Enhancements

• Upgrade Insulation: If the budget allows, exceed code-minimum insulation. For example, use closed-cell spray foam in walls (costlier, but adds R-value and air-seals in one step), or add rigid foam on top of the subfloor before finish flooring for extra floor warmth. A well-insulated ADU will save heating costs in Rapid City's cold winters.
• High-Efficiency HVAC: Consider a high-efficiency mini-split heat pump with a good SEER and HSPF rating for lower electric bills. Also, install a programmable thermostat or smart controls for the unit to optimize energy use.
• LED Lighting & Efficient Appliances: Use all LED light fixtures to minimize power usage and heat. Choose Energy Star-rated appliances (fridge, washer/dryer, etc.) to reduce electrical load – especially important if the electrical capacity is limited. An Energy Star fridge and a high-efficiency water heater (possibly a heat pump water heater, though those are pricier) can make the unit cheaper to run.
• Solar-Ready: If interested in sustainability, you could have an electrician make the unit solar-ready by running conduit to the roof. Rapid City has decent sun – a small solar array in future could offset the ADU's energy use.
• Air Sealing: In addition to insulation, focus on air-sealing the building envelope. Use foam/caulk at all penetrations and double-check weatherstripping on doors and windows. A tight envelope improves efficiency and comfort.
• Window Quality: Opt for double-pane low-E windows (standard now) or even triple-pane if within budget, for better insulation. Also, install good blinds or curtains; they help with both privacy and insulation (closing them on cold nights).

Layout and Space Optimization

• Efficient Layout: Keep the kitchen and bathroom close together (which the plan does by using existing plumbing wall). This reduces long pipe runs and makes the best use of space. An open concept kitchen/living room not only feels larger but also simplifies HVAC distribution (one open area easier to heat/cool).
• Pocket Doors/Sliding Doors: In tight areas (like the bathroom or closets), consider using pocket doors or sliding barn-style doors. This eliminates door swing space, making small rooms more usable. For example, a pocket door on the bathroom can save wall space in the hall/living area.
• Built-In Storage: Maximize storage with built-ins. E.g., built-in shelves or cabinetry in any wall niches, or above the washer/dryer, will help tenants or occupants have enough storage in a small unit. You could also utilize the attic space (if one is created) for storage by finishing a small portion or at least having pull-down stairs for accessible storage of seasonal items.
• Bedroom Layout: Ensure each bedroom has at least one wall where a queen bed can fit without blocking a door or window. You might plan to put the closets between the bedrooms as a sound buffer. Also, placing the closets on interior walls (instead of taking up exterior wall space) keeps exterior walls free for windows and furniture.
• Multi-functional Furniture: Although not a construction task, consider the eventual furnishing – for instance, in the living area, a kitchen island that doubles as a dining table, or a built-in desk in a bedroom if it might be used as an office/guest room. Planning for these during construction (like providing outlets or lighting in those areas) can improve usability.
• Light and Ventilation: Strategically placed windows will provide cross-ventilation and natural light, making the space feel larger. Since it's an open living/kitchen, having windows on at least two sides (for example, one on the front and one on the back or side) will greatly improve the ambiance. A sun tube or skylight could even be added in a central area (optional) to bring light into the middle of the unit.
• Privacy: If the ADU will be rented, consider privacy from the main house – maybe install a fence or landscaping. For the interior, if bedrooms will be next to each other, that insulation in interior walls for sound damping is a good idea so occupants don't disturb each other.

Long-Term Durability and Maintenance

• Moisture Protection: Given the CMU construction, apply a masonry sealer or waterproofing coat to the exterior of the block walls before insulating inside. This prevents any moisture wicking through the block and into your insulation/drywall. Also, ensure good caulking at all exterior joints. In the bathroom, use cement backer board and a waterproof membrane (like RedGard or similar) behind any tiled areas to prevent moisture damage over time.
• Siding and Exterior Materials: Use durable, low-maintenance materials on the exterior. For example, fiber-cement siding or stucco (which is common on block) that can last decades. Avoid wood siding that needs frequent painting. If painting block, use elastomeric paint that can bridge hairline cracks and resist moisture. All exterior wood trim should be primed and painted or use PVC trim boards to avoid rot.
• Flooring Durability: The chosen LVP flooring is an excellent durable choice (waterproof and scratch-resistant). Use quality LVP that has a good wear layer so it holds up to tenants or heavy use. In the entry, consider a heavy-duty doormat or a tiled entry pad to handle water and dirt from shoes.
• Fixtures and Hardware: Choose plumbing fixtures with metal parts (avoid cheap plastic) for longevity. Mid-grade faucets (Moen, Delta, etc.) will last longer and have readily available replacement parts like cartridges. Similarly, for the shower, a pressure-balanced valve is code (prevents scalding) and good quality ones will last. Consider an elongated bowl toilet with a good flush rating (for tenant satisfaction and fewer clogs).
• Heating Back-up: While the mini-split will provide heat, Rapid City can be very cold, so it's wise to have a backup heat source. This could be the electric baseboard heaters or even just an electric plug-in heater kept in the unit for emergencies. Ensuring the insulation and tightness will keep it comfortable even if primary heat is out for a short while.
• Foundation and Pest Protection: Seal any gaps at the base of the walls or the new framing to prevent pests (mice, insects) from entering. Use foam or caulk at sill plates. Also, if termites are a concern in the area, consider treating the perimeter or using termite shields since you introduced wood framing inside a previously all-masonry structure.
• Fire Safety: Even though it's a small unit, a fire extinguisher in the kitchen area is a good addition. Also, using interconnected smoke alarms with the main house (if feasible wirelessly) could be an extra safety measure – though code will treat them separately since it's detached.
• Code Updates: The project as described meets 2025 code expectations, but remember that codes update over time. Building slightly above code (e.g., a bit more insulation or better windows) is future-proofing for both energy costs and any later inspection (for example, if selling the property, an inspector will appreciate that things were done well).

By following this plan and considering the above recommendations, the garage can be transformed into a comfortable, efficient, and durable 2-bedroom home. It will add significant utility and value to the property, whether used for family or rented out. The cost and timeline are substantial but in line with creating a full legal dwelling unit out of a bare structure. With careful planning, adherence to Rapid City's codes, and maybe some sweat equity, the project can be completed successfully – yielding a brand-new living space that should serve well for years to come.

Sources:

• Garage/ADU conversion cost ranges and considerations  
• Average permit costs and required permit types 
• ADU definition and size limit in South Dakota (800 sq.ft.) 
• Timeline variability for garage conversions (weeks to months) 
• Bathroom addition cost factors (midrange full bath ~$5k–$15k)