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ADU / Backyard Cottage in Castle Rock
Licensed adu / backyard cottage services for Castle Rock and Douglas County. Build an income-producing unit in your backyard.
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Local Service
ADU / Backyard Cottage Services in Castle Rock, Colorado
Autotelic provides professional adu / backyard cottage services throughout Castle Rock and the surrounding Douglas County area. Accessory dwelling unit construction across the Denver metro — detached new builds, garage conversions, and basement conversions compliant with Colorado HB 24-1152. One veteran-owned design-build team runs the full Denver sequence under a single contract: zoning verification and concept design, municipal zoning and building permit reviews, then construction and inspections through certificate of occupancy. Whether you're in Castle Rock (Douglas County seat) or nearby communities, our team delivers quality workmanship backed by Colorado licensing and full insurance coverage.
Permit Thresholds
Castle Rock permit thresholds
- Code reference
- Exempt work follows the Town’s adopted amendments to the 2024 International Residential Code (IRC) and International Building Code (IBC), per Ordinance No. 2026-017 (effective around June 30, 2026).Ordinance No. 2026-017
- Code reference
- One-story detached accessory non-habitable structures (tool sheds, playhouses, etc.) ≤ 120 sq ft, ≥ 10 ft from the nearest occupiable structure.
- Code reference
- Fences ≤ 6 ft high (swimming pool barriers of any height are *not* exempt).
- Code reference
- Shingle repair or replacement not exceeding one square (100 sq ft) of covering per building.
- Code reference
- The adopted codes (2024 IRC/IBC and related) govern when alterations trigger permitting.
- Code reference
- See Title 15 of the Castle Rock Municipal Code (and amendments in Ordinance 2026-017) for the full adopted code language on work exempt from permit (primarily amending IRC R105.2 and equivalent IBC sections).Ordinance 2026-017
- Building use tax
- 5.2% applied to 50% of the project’s valuation (materials estimated at half the valuation).
- Code reference
- This comprises the Town’s 4.2% use tax rate + Douglas County’s 1% use tax rate.
Codes are amended regularly — verify current requirements with **The Town of Castle Rock Building Division (part of Development Services) issues residential building permits within the town limits.
Zoning & ADU
Castle Rock zoning & ADU quick facts
- Code reference
- R-1 Single-Family Residence District (primary/most common single-family district; Chapter 17.18) and R-2 Single-Family and Duplex Residence District (Chapter 17.22) are the relevant standard single-family zones.
- Max lot/building coverage
- R-1 and R-2 references indicate standards such as 40% building coverage in certain contexts or related districts (e.g., older or specific provisions); exact R-1/R-2 figures not uniformly detailed in accessible summaries without full code access.
- Max building height
- R-1/R-2: Principal buildings 35 feet; accessory buildings/structures (including garages) 20 feet (Chapter 17.22.040 for R-2; consistent descriptions for R-1).
- ADU permitted
- Yes in R-1 and R-2 (and other single-family residential zones/PUDs designated for single-family use), as an accessory use to single-family detached dwellings.
- Code reference
- One ADU per lot; administrative review/building permit (updated per state HB requirements and local Chapter 17.61).
- ADU max size
- Interior/attached ADUs up to 50% of primary dwelling or 750 sq ft (whichever greater); detached ADUs generally ~800 sq ft (per 2025 code update summaries; exact code limits in 17.61).
- Setbacks (R-2 example, consistent with R-1 descriptions)
- Front yard (all buildings) 25 feet; rear yard principal buildings 25 feet, accessory 10 feet; side yard per dwelling 5 feet (accessory buildings 2 feet if in rear one-third of lot, otherwise 5 feet).
- R-1
- Principal front/rear typically 25 feet.
Codes are amended regularly — verify current requirements with **The Town of Castle Rock Building Division (part of Development Services) issues residential building permits within the town limits.
Energy Code
Castle Rock energy code quick facts
- Code reference
- 2021 International Energy Conservation Code (IECC), with local amendments, as adopted by Ordinance No. 2026-017 (adopted June 2, 2026; effective June 30, 2026), along with the Colorado Model Electric-Ready and Solar-Ready Code.Ordinance No. 2026-017
- Code reference
- This applies to Castle Rock (Douglas County, Climate Zone 5B).
- Code reference
- The adoption aligns with state requirements for jurisdictions updating other building codes by the June 30, 2026 deadline.
- Code reference
- Specific local numeric amendments to prescriptive requirements (e.g., R-values, U-factors, or air-sealing thresholds for remodels/additions) are not detailed in publicly available sources beyond references to the base 2021 IECC tables/sections (such as Table R402.1.2 for insulation/fenestration and
- Code reference
- The adopting ordinance incorporates the 2021 IECC by reference with amendments thereto but does not appear to alter the core prescriptive values in available excerpts.ordinance incorporates
Codes are amended regularly — verify current requirements with **The Town of Castle Rock Building Division (part of Development Services) issues residential building permits within the town limits.
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What an ADU or backyard cottage involves
An accessory dwelling unit (ADU), sometimes called a backyard cottage, is a secondary living unit on a lot that already has a primary home. Common forms include detached backyard cottages, garage conversions, and attached additions with a separate entrance and living space. In the Denver metro, feasibility usually turns on zoning and lot standards, utility capacity, access and parking rules, setbacks, height limits, and how the unit will be used (long-term housing, multigenerational living, or flexible guest space). Early planning should confirm what your city or county allows on your specific parcel before design is locked in.
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Design and site factors that drive the project
Strong ADU plans start with the lot, not just the floor plan. Key inputs include buildable area after setbacks, existing structures and easements, grading and drainage, tree and landscape impacts, alley or side-yard access, and where water, sewer, gas, and electric can connect. Interior planning typically covers a compact kitchen, full or three-quarter bath, sleeping space, storage, daylight, and code-required egress. Exterior design should fit the primary home and neighborhood context while meeting height, lot coverage, and exterior material standards set by the local jurisdiction. Detached units also need clear decisions on foundation type, insulation and energy detailing for Colorado’s climate, and durable exterior assemblies that handle freeze-thaw cycles and sun exposure.
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Permits, inspections, and trade coordination
ADU projects generally require building permits and may also need zoning review, utility permits, and separate trade permits. Requirements vary by city and county across the Denver metro, so the submittal package should match the rules for the property address. A municipally licensed Denver general contractor coordinates the overall project and works with licensed specialty trades for work such as electrical, plumbing, and mechanical systems. That coordination covers sequencing, inspection readiness, and keeping architectural, structural, and MEP details aligned as the unit moves from plans to construction.
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Typical build path
Most ADU projects follow a clear sequence: feasibility and code check, measured site review, schematic design, construction documents, permit submittal, procurement, construction, inspections, and closeout. Detached cottages often involve site work, foundation, framing, roofing, windows, insulation, drywall, finishes, and final utility tie-ins. Garage conversions and attached ADUs can reduce some site work but may add structural, fire-separation, moisture, and existing-condition challenges. Conversion projects need careful assessment of foundation, framing, insulation, head height, and whether the existing shell can support a comfortable, code-compliant dwelling.
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What influences cost without a one-size price
ADU cost is project-specific. Major drivers include unit size, detached versus attached or conversion scope, foundation and site work, utility run lengths and capacity upgrades, kitchen and bath layout, finish level, structural complexity, energy detailing, access constraints, and local permit requirements. Soft costs also matter: design and engineering, survey or site documentation when needed, permit fees, and longer lead times for selected materials. A clear scope and early utility/site review usually reduce redesign and change orders later.
FAQ
Common questions
What is the difference between an ADU and a backyard cottage?
They often describe the same idea: a secondary dwelling on a lot with a primary home. “Backyard cottage” usually means a detached unit behind the main house. “ADU” is the broader planning term and can include detached units, attached units, or conversions, depending on local definitions.
Who handles the trade permits and licensing on an ADU project?
A municipally licensed Denver general contractor coordinates the project and the permit path. Licensed specialty trades perform regulated trade work such as electrical, plumbing, and mechanical, and those trades pull the permits required for their scopes where applicable.
Can every Denver-metro lot add an ADU?
No. Eligibility depends on local zoning and lot standards, including use rules, setbacks, height, lot coverage, parking, and utility constraints. The right first step is confirming what the jurisdiction allows for the specific address and lot configuration.
Is a garage conversion simpler than a new detached cottage?
Sometimes, but not always. Conversions may reuse an existing shell and reduce some site work, yet they can require structural upgrades, insulation and moisture improvements, fire separation, ceiling-height solutions, and new utility routing. A detached cottage adds foundation and full exterior scope but can offer a cleaner layout when yard space and setbacks allow.
How long does an ADU project usually take?
Timeline depends on design complexity, utility work, permit review duration, material lead times, weather, and inspection scheduling. Projects with clear feasibility, complete drawings, and fewer existing-condition surprises generally move more predictably than conversions discovered midstream to need major upgrades.
What decisions should homeowners make early?
Confirm intended use, target size, detached versus attached or conversion, access and privacy needs, parking implications, budget range as a planning input, and whether the unit must function independently year-round. Those choices shape site layout, utility design, and the permit strategy.
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How to start planning
Begin with parcel realities: zoning path, buildable envelope, access, and utility capacity. Then define the unit type and must-have program so design and budgeting stay aligned. From there, construction documents and permit coordination can proceed with fewer revisions. If you are comparing options, bring basic lot information, any prior survey or improvement location certificate if available, rough size goals, and notes on how the unit will be used. That preparation helps a general contractor and design team give a clearer read on scope and sequence.
Service Area
Serving Castle Rock and Douglas County
We serve Castle Rock, CO and all surrounding Denver metro communities. Our team is based in Denver and operates throughout the Front Range, from Castle Rock to Longmont and everywhere in between. Contact us for a free estimate on your Castle Rock project.
FAQ
Common questions
Is an ADU allowed on my lot?
It depends on your city’s zoning — lot size, setbacks, and parking rules vary across the metro. We run the zoning check as the first step and tell you what your lot supports before you spend money on design.
Do you handle ADU permits and inspections?
Yes — ADU permitting is municipal, and we manage zoning review, permit application, and every inspection through certificate of occupancy.
Detached, attached, or garage conversion — which is right?
Each has different zoning, cost, and site implications. We design all three and recommend based on your lot, budget, and how you plan to use the unit.
What does an ADU cost?
Getting a real answer costs less than most people expect: an ADU feasibility consultation is $350, and the full ADU feasibility package — zoning check, site analysis, and concept direction — is $950, both listed at fixed prices on our booking page. Construction cost depends on the path: garage and basement conversions reuse existing structure, while a detached backyard cottage is new construction from the foundation up. After feasibility we quote the build itself as a fixed-price proposal, so you know the number before work starts.
How long does an ADU project take?
Three phases run in sequence: design (site measure, concept, construction documents), permitting (zoning and building review, which move on the municipality’s calendar), then construction. Conversions generally move faster than detached new builds because the shell and foundation already exist. We lay out the phase-by-phase schedule in your proposal, and you track progress on our operations platform once work starts.
How small a lot can support an ADU?
Smaller than most people assume — many Front Range single-unit lots that owners write off can carry a detached unit, and each city sets its own minimum lot size, setbacks, and building coverage. Whether your district’s standards leave room for a backyard cottage — or point you toward a garage or basement conversion instead — is exactly what the feasibility check answers for your address.
What is the ADU permit process?
Two municipal reviews run in order: a zoning review confirming the unit fits your district’s standards, then a building permit review of the construction documents, with inspections during the build and a certificate of occupancy at the end. Colorado HB 24-1152 now requires most Front Range municipalities to allow ADUs on single-unit lots, and we confirm how your city implements it as the first step of feasibility.
How It Runs
01
Survey
02
Design
03
Build
04
Verify
DESIGN SERVICES
Discovery & Site Analysis
Needs + preference programming, site survey, as-built documentation, feasibility.
We walk, measure, and photograph your property — existing conditions, utilities, structure, and constraints. You get the as-built documentation and feasibility read that every later decision rests on.
Learn more →Concept Design & Space Planning
Schematic design, floor plan studies, layout options.
Your scope becomes schematic floor plans you can compare side by side — circulation, daylight, adjacencies, and what each option does to the budget. Layout decisions happen on paper, where changes are cheap.
Learn more →Architectural Design & 3D Renderings
Design development, materials + finishes, photorealistic visualization.
The chosen concept resolves into materials, finishes, fixtures, and lighting — with the automation layer drawn in. Photorealistic renderings let you walk the space and adjust before anything is priced.
Learn more →Construction Documents & Permitting
Full CD sets, structural + MEP engineering coordination, permit-ready drawings.
Approved designs become coordinated architectural, structural, and MEP sheets — the set your jurisdiction permits from and trades build from. We submit, track, and answer review comments.
Learn more →CONSTRUCTION
New Construction & Custom Homes
Ground-up homes and light commercial, dirt to keys.
Ground-up residential and light commercial builds — foundations through finishes, including modular and steel construction. One accountable builder from dirt to keys.
Learn more →Remodels & Additions
Kitchens, baths, basements, pop-tops, whole-home.
Kitchens, baths, basements, pop-tops, and whole-home renovations that respect the house you already have. We handle structure, permits, and the dust.
Learn more →Commercial Tenant Finish & Build-Outs
Shells to working spaces — retail, office, restaurant, school.
Raw shells become working spaces — showrooms, offices, restaurants, schools. Dealer-spec finishes, code compliance, and opening dates held.
Learn more →ADUs & Modular Construction
Backyard cottages, garage conversions, factory-built homes.
Backyard cottages, garage conversions, and factory-built homes — zoning, design, permits, and set. Denver’s ADU rules are a specialty, not a surprise.
Learn more →Outdoor Living & Patio Structures
Decks, pergolas, and dining patios built for Colorado weather.
Decks, pergolas, and dining patios engineered for Colorado sun, snow, and hail — structure, shade, and drainage done right the first time.
Learn more →TECHNOLOGY
Smart Home Automation
Lighting, shades, climate, audio, security — one interface.
Whole-home control of lighting, shades, climate, audio, and security from a single interface — Crestron, Lutron, Savant, and Control4 designed in, not bolted on.
Learn more →A/V Systems
Theaters, distributed audio, video walls, commercial sound.
Theaters, distributed audio, video walls, and commercial sound — designed, installed, and tuned by the same team for over 20 years.
Learn more →Control Systems
Custom programming — scenes and schedules that fit the space.
Every subsystem brought into one elegant interface — custom programming for homes and venues, with scenes and schedules that match how the space is actually used.
Learn more →Networking & Edge Compute
Enterprise Wi-Fi, structured cabling, racks, on-prem compute.
Enterprise-grade Wi-Fi, structured cabling, racks, and on-premise compute — the backbone that makes everything else reliable, including our own Barbot platform.
Learn more →Solar & Energy Storage
Solar arrays, Tesla Powerwall, EV charging — certified install.
Solar arrays, Tesla Powerwall, and EV charging designed and installed by a Tesla Energy Certified team — roof, electrical, and app in one scope.
Learn more →TRUSTED TO BUILD FOR
- Punch Bowl SocialFirst four locations
- Spectrum RetirementSenior living communities
- Denver HighlandsFirst modular custom home
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