Home Addition Cost Summary — Denver, Colorado
Use this table to quickly scope your home addition budget. Costs below reflect Denver metro pricing as of April 2026.
| Project Scope | Low End | Average | High End |
|---|---|---|---|
| Bump-Out Addition (100–200 sq ft) | $22,000 | $55,000 | $95,000 |
| Room Addition (400–600 sq ft) | $75,000 | $155,000 | $260,000 |
| Second Story Addition (800–1,200 sq ft) | $130,000 | $280,000 | $500,000 |
| ADU / Accessory Dwelling Unit (400–600 sq ft) | $80,000 | $160,000 | $280,000 |
| Typical Home Addition (Denver) | $50,000 | $155,000 | $380,000 |
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4 Factors That Affect Home Addition Cost in Denver
Understanding what drives cost helps you make smarter decisions and negotiate with contractors more effectively.
- Snow load and insulation — Denver additions require R-38+ attic insulation, R-19+ wall insulation, and structural framing sized for snow loads; adds $8,000–$18,000 to mechanical and framing costs
- ADU demand — Denver has one of the fastest-growing ADU (accessory dwelling unit) markets in the US; ADU additions command premium rents ($1,600–$2,800/mo) and strong resale premiums
- Labor market tightness — Denver construction labor has risen 30–40% since 2020 due to population influx; GC overhead and profit typically runs 25–35% on Denver addition projects
- Altitude energy code — Colorado Energy Code requires high-performance windows (U-factor ≤ 0.30) and air sealing in additions; quality window packages add $4,000–$12,000 over minimum-code options
How to Keep Home Addition Costs Down in Denver
Getting competitive bids is the single most effective cost-control strategy. In Denver's active construction market, price spreads between contractors can be 20–40% for identical work.
- Get at least 3 written bids — verbal quotes are not bids
- Check contractor licenses with the Colorado Department of Licensing and Regulatory Affairs
- Use our Markup Calculator to verify contractor margins are reasonable (25–35% overhead + profit is fair)
- Schedule work in off-peak months when contractor calendars have openings and rates dip
- Separate materials from labor in your contract — buying materials direct can save 10–20% on markups
Frequently Asked Questions
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How much does a home addition cost in Denver, CO?Home additions in Denver range from $50,000 for a small bump-out to $380,000+ for a large second-story addition. The average 400–600 sq ft room addition runs about $155,000 fully finished — among the higher costs in the Mountain West. Denver's labor shortage, strict energy codes, snow-load structural requirements, and surging real estate demand all push costs higher. Per-sq-ft addition costs in Denver run $230–$310 all-in for mid-range finishes.
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Should I add an ADU in Denver?ADUs (accessory dwelling units) are a particularly strong investment in Denver right now. Denver's ADU-friendly zoning (most residential lots are ADU-eligible since 2022 reforms) and sky-high rent market ($1,800–$2,800/mo for a quality ADU) mean you can often achieve 6–8% cap rates. ADU construction in Denver runs $180–$260/sq ft all-in. With financing options like HELOCs, the cash-on-cash returns are compelling. Check Denver Community Planning and Development's ADU resources before designing.
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How long does a home addition take in Denver?A Denver home addition takes 5–9 months total from first architect meeting to completion. The City and County of Denver plan review for residential additions takes 4–10 weeks (expedited review is available for a fee). Construction runs 12–20 weeks depending on size. Factor in 6–10 weeks of pre-permit design work. ADUs follow a similar timeline but benefit from Denver's dedicated ADU permit pathway, which can reduce review time to 2–4 weeks for pre-approved plans.
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