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Apprentice answer

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

3rd YearRoof Curbs, Louvers & Exterior AirCheck 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.

Field checklist

Ask Foreman

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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