Context
User is building a 24’x40’ garage with a loft apartment (A-frame style roof). The structure will be finished outside (roof, siding, windows, doors) but the interior will remain unfinished for later work. Plans include radiant slab heating downstairs and a future mini-split upstairs. Bathroom, kitchen, and laundry appliances will be upstairs and require proper venting and rough-in planning.
Key Points
- Best to install a main plumbing vent stack through the roof during initial build, even if capped inside for now.
- Vent pipe can run horizontally in the triangular attic cavity above fixture flood level with slope back to drain.
- Only the roof vent stack is essential now; other vents (bath fan, dryer, kitchen hood) can be stubbed or planned for later.
- Grouping appliance vents on the gable end wall is preferred over roof or soffit penetrations.
- Each vent (dryer, hood, bath fan) must have its own duct/termination with proper spacing and backdraft dampers.
- Dryer vent must use rigid metal duct, terminate outside (not soffit/attic), and stay within length limits.
- Stub-outs and sleeves (water, sewer, gas, electrical, conduit) should be run through slab during pour.
- During framing, consider hose bibbs, exterior outlet boxes, conduit for future solar, and mini-split refrigerant line sleeves.
- Temporary capping of roof vent inside is acceptable; rainwater is minimal and will drain once tied into sewer.
Actions
- Install 3” roof plumbing vent during initial build (capped inside until tie-in).
- Plan gable end terminations for bath fan, kitchen hood, and dryer vents (individual ducts, spaced ≥3’). — stage:: 5
- Rough-in hose bibbs on exterior walls. — stage:: 3
- Add exterior electrical box for mini-split and sleeve for line sets. — stage:: 3
- Leave conduit stubs for future data, solar, and low-voltage wiring. — stage:: 3
- Document framing, slab penetrations, and PEX layout for future work. — stage:: 2