The short answer: The lip at a garage can reflect movement of the driveway panel, the garage floor or both. Show the full approach, doorway and drainage so the lift target does not create a different step or send water toward the building.
The ground at the garage was dug up once
When the house was built, a trench was dug for the garage footing and stem wall, the concrete was poured, and the trench was filled back in. That backfill is loose compared with the ground beside it, and it keeps packing down for years. The garage floor rides on the footing or on a pad that was compacted on purpose, so it stays put. The apron sits on the trench.
That is why the step shows up right at the door. The garage side is held up, the driveway side rides on soil that is still settling, and the joint between them is where the difference shows. A driveway poured months after the house, over fill that had barely begun to settle, often drops the most.
Where the water comes from
Settling backfill drops a slab slowly. Water drops it fast. The roof edge over a garage door often has no gutter, or a downspout that quits a foot from the wall, so every storm puts a sheet of water on the joint. On many lots the driveway slopes toward the door, so the apron is also the low point it drains to.
New Mexico ground makes this worse two ways. Caliche near the surface does not soak water up, so it runs sideways and scours loose soil from under a slab edge. Dry, loose soils do the opposite: they hold up until a monsoon soaks them, then compact and drop. Either way the apron loses its footing first.
Reading the lip at the door
The shape of the drop says a lot. A lip that is even across the door means the whole panel settled, usually backfill. A corner lower than the rest points to washout on that side, often under a downspout or a dripping hose bib. A crack across the apron with one side lower means the panel broke and the pieces move on their own.
Look at the garage side too. If the floor inside has a crack running from the door, if the door no longer seals evenly against the floor, or if the floor feels out of level, the garage slab may have moved as well. That turns a driveway lift into a foundation question, and we would rather know before anyone drills.
What a lift does at the door
The target at a garage is the floor inside. We measure the lip, check which way the panel should fall so water keeps running away from the door, and mark injection points along the low edge and out across the panel. The holes go near the joint first, where the gap under the slab is deepest.
The foam goes in a little at a time. It fills the washed-out space under the edge before anything moves, then begins to raise the slab. We watch the lip close against the garage floor and stop at the floor rather than pushing past it. The holes get patched, and the written estimate says when cars can use the apron again.
What lifting will not fix at the garage
A lift puts the apron back where it was. It does not stop the roof water that moved the soil, so a downspout that empties at the door still needs to be carried away from the slab, and the joint between apron and floor is worth sealing afterward so storm water stops running into the gap. Hardware-store joint sealant does it.
If the garage floor is the piece that moved, lifting the driveway only changes where the step is. That is a foundation question, and we check for it at the visit. An apron broken into many small pieces is a replacement, not a lift, and we say so rather than drill it.
What to have ready before you call
A few photos tell us most of what we need before we come out. Shoot the step straight on from outside with the garage door open, then along the joint from the side, then the roof edge and downspouts above it. A tape laid across the lip gives us the height.
Add a line about the history: roughly when the step appeared, whether a wet summer made it worse, and whether the driveway was poured with the house or added later. Then the visit confirms the plan instead of starting from scratch. The short list:
- A wide photo showing the driveway and garage threshold together.
- Close views of the joint, cracks and any gap at the garage door.
- A note about water flow, downspouts or known leaks near the panel.
- The vehicles using the slab and any pipes or drains you know are beneath it.
In short
- The apron drops because it sits on the backfilled footing trench while the garage floor is held up.
- Roof water at the door and soils that scour or collapse speed the drop up.
- An even lip means settling; a low corner means washout; a crack with a step means a broken panel.
- A lift targets the garage floor, fills the washout first, and keeps the fall away from the door.