ADU & Small House Plans · Castle Rock, CO
ADU and Small House Plans in Castle Rock, CO
Looking to buy ADU and small house plans in Castle Rock, CO? HousePlans USA draws ADU and small house plans from scratch for the Castle Rock, CO area. Two or more designers sketch concepts for your lot, you pick your favorite, and permit-ready plans arrive in as little as 24 hours.
From $1,050 · free customization · 30 days of free revisions · pay 75% to start
Why buy ADU and small house plans for Castle Rock, CO from us
Small homes work harder than big ones: every foot has to earn its place. A backyard ADU can house a parent, earn rent or become a home office.
We draw studios, one- and two-bedroom cottages, garage apartments and affordable starter homes to your city's size, height, setback and parking rules.
ADU rules handled
Size, height, setback and parking limits are checked for your lot before concepts begin.
Live large in less
Vaulted ceilings, lofts and built-in storage make small rooms feel open.
Build it again
PDF unlimited build rights for $395 let you reuse the plan on more lots.
What's included in your ADU and small house plans
- Studio, 1-bedroom and 2-bedroom layouts
- Garage apartment with fire separation details
- Utility routing from the main house
- Aging-in-place details on request
- Unlimited-build rights available for investors
Plan prices by size
| Up to 1,000 sq ft | $1,050 |
| 1,001 – 1,500 sq ft | $1,295 |
| 1,501 – 2,000 sq ft | $1,495 |
| 2,001 – 2,500 sq ft | $1,695 |
| 2,501 – 3,000 sq ft | $1,895 |
| 3,001 – 3,500 sq ft | $2,195 |
Colorado engineer stamp from $750. See every option on our pricing page.
Where to get your Castle Rock building permit
No permit is released without an approved erosion control plan. The 2025 Colorado Wildfire Resiliency Code took effect July 1, 2026.
Checked November 2026. Offices and rules change, so confirm with the office before you apply.
Building requirements
Building a house in Castle Rock, CO: what the code requires
Codes adopted locally (no mandatory statewide code)
- Building code
- No statewide residential code. Counties and cities adopt IRC editions with amendments (Denver has its own Denver Building Code).
- Energy code
- State law requires jurisdictions that update codes to adopt a recent IECC edition plus electric- and solar-ready provisions.
- Climate zone
- IECC climate zone 4–7. Insulation, windows and HVAC are sized to match.
- Typical frost depth
- 30–36 in (Front Range), 36–48 in+ (mountains). Footings must extend below the local frost line (confirm with your building department).
- Foundations
- Crawlspace or basement, depending on soil and lot slope.
- Who can draw the plans
- Single-family homes can generally be designed by a non-licensed home designer. A licensed engineer's stamp is often required for structural items, engineered foundations or special hazard zones, or when the local building official asks for it.
- Engineer stamp
- If your jurisdiction requires sealed drawings, add our Colorado Engineer Stamp / Permit-Ready package ($750).
Colorado-specific rules & hazards
- Mountain counties commonly require engineered foundations, high snow loads (often 50–100+ psf) and wildfire mitigation.
- Expansive soils along the Front Range often require a soils report and engineered foundation.
- Heavy roof snow loads and steeper, well-braced roof framing
- Wildfire-resistant materials and defensible-space detailing
Summary for planning only. Codes, editions and local amendments change, so always confirm current requirements with the building department that will issue your permit. Our designers check your jurisdiction before drawing.
Cottage homes we can draw for Castle Rock, CO
Style inspiration photos, not homes built in Castle Rock, CO or by HousePlans USA.
How ordering works
- 1
Get inspired
Pick the exterior styles and interior looks you love, or paste links to plans you've seen online.
- 2
Design & instruct
Choose rooms, size, basement, garage and your state, and tell our designers exactly what you want.
- 3
Compare 2+ concepts
Two or more designers each sketch a concept. Pick your favorite designer to draw the full plans.
- 4
Download & revise
Plans arrive by email and in your dashboard by your deadline. Revisions are free for 30 days.
Full guide: ADU and small house plans in Colorado
ADU and Small House Plans in Castle Rock, CO: FAQ
Can I build an ADU in Castle Rock, CO?+
In many cities, yes, but size, setback and parking rules vary. We check your lot's rules before we sketch.
Do you draw garage apartments?+
Yes. We draw one- and two-bedroom apartments over garages, including the required fire separation.
How much do ADU and small house plans cost in Castle Rock, CO?+
Custom plans start at $1,050 for homes up to 1,000 sq ft and are priced by size. Most family homes come to $2,000–$3,000 all-in, with free customization and 30 days of revisions.
How fast can I get ADU and small house plans for Castle Rock, CO?+
Standard delivery is 10 business days. Priority, Express, Rush (48 hours) and Super Rush (24 hours, up to 3,000 sq ft) are available at checkout.
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Let's design your home for Castle Rock, CO
It takes about 10 minutes, and we save your answers as you go.