Fort Collins, Colorado · Since 1973
Northern Colorado Roofing and Radon Specialists
Drennen Custom Contracting protects Northern Colorado homes from the top down and the ground up. Our roofing division builds complete, code-conscious roof systems for Colorado weather. Our licensed radon division tests buildings and designs mitigation systems for homes, real estate transactions, new construction, multifamily properties, schools, and commercial facilities.
Drennen has served Northern Colorado since 1973. Today, roofing and radon are our two defining specialties - each led by experienced people, supported by detailed documentation, and backed by a local company that understands the entire building.
Two Specialties. One Building-Wide Perspective.
Roofing
Roof replacement, repair, Class 4 and SBS systems, inspections, certifications, ventilation, warranties, insurance education, and local project pricing.
Explore Roofing ServicesRadon
Licensed testing, mitigation, crawl-space systems, passive activation, repairs, real estate support, new construction, large-building testing, and documented post-mitigation results.
Explore Radon ServicesDrennen is not a generalist claiming to do everything. Roofing and radon are established specialty departments with different trained teams, regulated scopes, and technical systems - connected by one local contractor that understands how the whole building works.
Why the Combination Matters
Roof and Ventilation Coordination
Roof performance depends on underlayment, flashing, decking, intake and exhaust ventilation, penetrations, drainage, and the building below - not shingles alone.
Radon and Building Coordination
Radon routes may intersect crawl spaces, slabs, framing, siding, electrical work, firestopping, attics, and roof penetrations. A building-wide contractor can plan those interfaces while keeping the radon work under the required licensed program.
Real Estate Documentation
Drennen provides roof inspections and certifications, licensed radon testing, mitigation proposals, post-installation results, warranties, and records that can be understood by buyers, sellers, brokers, and property managers.
New Construction
We can coordinate radon soil-gas control before concealment and roofing or ventilation decisions as the building takes shape, reducing expensive rework later.
Start With the Problem You Need to Solve
I Need a Roof Estimate
See Fort Collins roof-replacement cost ranges, Class 4 and SBS systems, project pricing, repairs, warranties, and service areas.
Learn moreI Have a Radon Result
Understand the number, licensing, mitigation options, cost ranges, post-testing, and what information to send for a proposal.
Learn moreI Am Buying or Selling
Access roof inspections and certifications, real estate radon testing, Realtor licensing guidance, insurance education, and closing coordination.
Learn moreI Am a Builder or Property Manager
Review new-construction radon requirements, licensed supervision, large-building testing, passive systems, roofing, maintenance, and portfolio documentation.
Learn moreProof, Not Just Promises
- Detailed scopes that identify what is included
- Current license, insurance, warranty, and credential information available for verification
- Real project photography and anonymized project examples
- Post-work documentation and testing where applicable
- Local office and long-term service rather than a storm-season or transaction-only presence
Featured Guides
2026 Roof Replacement Cost in Fort Collins
Transparent roof-planning ranges, project examples, scope comparison, and questions to ask bidders.
Read guide2026 Radon Mitigation Cost in Fort Collins
Planning ranges for passive activation, slab, crawl-space, mixed-foundation, complex, and service work.
Read guideColorado Radon Requirements for Realtors
Disclosure, licensed testing and mitigation, vendor verification, transaction timing, and documentation.
Read guideColorado Radon Requirements for Builders and Contractors
Who can legally perform radon work, direct supervision, new-construction standards, coordination, and common failures.
Read guideServing Northern Colorado
Drennen serves Fort Collins, Loveland, Windsor, Wellington, Timnath, and surrounding Northern Colorado communities. Service availability, travel, local permitting, and project type are confirmed for each address.
Talk With a Local Specialist
Tell us whether the concern is roofing, radon, a real estate deadline, new construction, or a project involving both building systems. The office will route the request to the correct specialty team.
Credentials, service areas, prices, warranties, and regulations can change. Verify current information in the written proposal and official licensing records.
608 East Trilby Road, Fort Collins, Colorado 80525 | [email protected] | 970-482-9100