Why is a garage floor expected to slope toward the vehicle door?

A garage floor collects things the rest of the house does not: fuel and oil dripping from vehicles, washing water, and in cold climates a great deal of snow melt carried in on a car. All of it needs somewhere to go, and the design answer is a slope toward the vehicle door so the liquid runs out to the driveway rather than pooling against the walls or migrating toward whatever is on the other side of them. The house side is the concern — a floor sloping inward carries fuel vapour and liquid toward the door into the dwelling and toward the wall assembly, and standing water at that junction rots the sill and bottom plate. The slope is also why the garage slab is typically poured below the house floor level. Where a floor slopes the wrong way, or is dead flat with standing water evident, the inspector reports it and notes the staining or deterioration that confirms it.

Fuel, oil, washing water and melted snow accumulate on a garage floor, and the slope carries them out through the vehicle door rather than letting them pool against walls or run toward the house.

Garage floors are sloped toward the vehicle door so spilled liquids and melt water drain outside rather than pooling or migrating toward the dwelling. The garage slab is typically set below the adjacent house floor.

Downhill and Out the Door. Whatever drips off the car should leave the way the car came in.

Check the sill and bottom plate at the house wall where the floor slopes inward. Decay there is the consequence that makes the finding worth reporting.

• •Reporting the slope direction without checking for consequent decay
• •Missing a flat floor with evidence of standing water
• •Treating the finding as cosmetic