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Apprentice Q&A · #110

What is a "doghouse" on a roof, and how do I flash duct penetrating the side of it?

3rd YearRoof Work & CurbsYELLOW · Check First

A Doghouse is a vertical sheet metal enclosure built on a roof to house large horizontal duct transitions entering the side of a mechanical penthouse or building wall.

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Plain-English answer

A Doghouse is a vertical sheet metal enclosure built on a roof to house large horizontal duct transitions entering the side of a mechanical penthouse or building wall.

To flash it, install an overhanging counter-flashing hood (shingle-style) above the duct penetration point. Run the lower sheet metal edges out over the roofing membrane so water sheds away from the opening like an umbrella canopy.

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Hey boss, I’m checking roof work & curbs: What is a "doghouse" on a roof, and how do I flash duct penetrating the side of it? I found the likely issue and want to verify the next step before I lock it in. Do you want me to adjust it now or check the drawing/detail first?

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Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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