About Drennen Custom Contracting

Drennen Custom Contracting is a local, family-run Northern Colorado company serving the community since 1973. Today, roofing and radon are Drennen's two defining specialties. Each has its own trained team, regulated or technical scope, written documentation, and long-term service support.

Two Specialties. One Building-Wide Perspective.

Roofing

Complete roof systems, repairs, Class 4 and SBS materials, inspections, certifications, ventilation, flashing, warranties, and detailed project scopes.

Radon

Colorado-licensed measurement and mitigation oversight, existing-home systems, crawl spaces, passive activation, repairs, real estate work, new construction, and large-building testing.

Why the Combination Matters

A roof is not an isolated surface. It interacts with roof decking, attic ventilation, penetrations, siding, drainage, and the rest of the building envelope. Understanding those connections allows Drennen's roofing team to identify problems that a surface-only inspection would miss and to write scopes that account for the full system.

A radon system is similarly embedded in the building. It interacts with slabs, crawl spaces, framing, electrical work, siding, attic conditions, roof penetrations, and trade sequencing. Proper design and installation require understanding how the building is constructed, not just where the pipe exits.

Roofing and radon remain distinct specialties with separate teams, separate licensing, and separate documentation. What they share is a single company that understands the whole structure — which matters when a project involves both systems or when a problem in one area has a root cause in another.

How Drennen Works

Detailed scopes that identify what is included
Current licenses, insurance, warranties, and credentials available for verification
Real Drennen project photography and anonymized project examples
Post-work documentation and testing where applicable
A local office and long-term service presence
Clear communication with homeowners, Realtors, builders, and property managers

Meet the Team

Office review required: Biographies and photographs are pending office confirmation. Contact the office to verify current roles and credentials before publishing.

Arnold Drennen

Owner