Why are my concrete steps pulling away from the house?

Concrete steps pull away from a house because the ground under them has settled or shifted, not because the concrete has failed. The steps are a heavy block that usually rests on soil, while the house rests on footings, so when the soil moves the steps go with it and the house stays put. A narrow gap that is not growing is mostly a water problem you can seal. A gap that keeps widening, or steps that tilt, sink or crack, need a contractor.

The usual causes

Settling backfill. When a house is built, the soil dug out for the foundation is pushed back against the walls, and front steps are often poured right on top of it. Fairfax County's guide to problem soils says backfill next to basement walls normally settles after several years, leaving depressional areas for water to collect.^[1] Steps sitting on that backfill settle with it, and they often drop or tip on the side nearest the house.

Water at the foundation. Fairfax County also notes that surface water can accumulate against foundation walls where the backfill has settled,^[1] softening the soil further. Roof water is often the source: the Northern Virginia Soil and Water Conservation District says an average sized home can experience hundreds of gallons of runoff coming from the roof^[2] in a hard rain. A downspout that empties next to the steps can wash soil out from under them.

Clay that shrinks and swells. Some soils, such as the marine clays found in parts of Fairfax County, shrink and swell as their moisture changes. Fairfax County says building settlement caused by high shrink-swell clays is most noticeable in dry seasons of the year,^[1] which is why a gap can appear or widen after a dry summer. Its guide also says large trees should be at least 20 feet away from the house,^[1] because their roots draw moisture out of the soil.

Shallow support and frost. Steps are often poured on soil with little or no footing beneath them. Decks are held to a deeper standard; Fairfax County's deck details call for footings to reach a frost depth of 24 inches minimum.^[4] Steps resting on shallow soil can shift as the ground freezes and thaws.

A gap is not always a defect

Concrete steps are usually separate from the house, so some joint at the wall is normal. Quikrete describes expansion joints as cuts in slabs, or the joints between walls and concrete slabs, that go completely through the slab to the base material,^[3] and says their purpose is to allow the concrete slab to expand and contract with temperatures changes, without cracking the slab.^[3] A thin, even joint between the top step and the wall is not itself a problem. What matters is whether it is growing, whether the steps are tilting, and whether water is getting behind them.

How serious is yours?

Probably minor: a narrow, even gap that has not changed between measurements, with level treads and a top step still at the door sill.

Watch closely: a gap wider at one end, steps that lean toward the house, or a top step that has dropped below the threshold.

Get it looked at: a gap that grows each season, steps that crack apart or rock, cracks in the foundation wall behind them, or water in the basement near the steps.

Keep records. For foundation cracks, Fairfax County suggests you measure and keep a record of the width and extent of the cracks and the time of the year,^[1] and the same habit works for a gap at the steps. A few dated measurements tell a contractor far more than one look.

What to do about it

Fix the water first. The district advises that ideally, a 5% grade should be maintained for a distance of ten feet around your home,^[2] and Fairfax County's guide says gutters and downspouts should carry all roof water beyond the backfill or at least ten feet away from the house.^[1] When you fill low spots, use a silty or clayey soil rather than sand, gravel, or mulch,^[1] which let water soak straight down beside the foundation.

Seal a stable gap. Quikrete says joints between walls and slabs need a flexible sealant to prevent water from penetrating the joint and deteriorating the sub-base.^[3] Its instructions say backer rod should be used for joints over 1/4 inch,^[3] pressed in deep enough, leaving a sealant depth of between 1/8 inch and 1/2 inch.^[3] Rigid mortar in the gap tends to crack out as the steps move.

Lift or rebuild if they have moved a lot. A contractor can sometimes raise a solid set of steps that has dropped evenly; how slab lifting works explains the methods. Steps that are cracked apart, badly tilted or sitting on soil that is still moving are usually replaced on a better base. Why concrete slabs sink covers the soil side in more detail.

Stop and call a pro if

• The gap keeps growing between measurements or opens and closes with the seasons.
• The steps tilt toward the house, rock underfoot or have cracked into pieces.
• The top step has dropped below the door sill and creates a trip at the doorway.
• The foundation wall behind the steps is cracking or water is getting into the basement.
• A handrail has pulled loose as the steps moved.

Diagnosing soil movement properly usually requires an individual experienced in soils and engineering,^[1] in Fairfax County's words, and a rebuild may need a permit; Christiansburg, for example, lists front porches among the work that needs a building permit.^[5] Virginia's Board for Contractors suggests you insist the contractor applies for all necessary building permits^[6] in its own name. For costs, see what concrete steps cost in Virginia, and for surface damage on steps that are otherwise sound, how to fix crumbling concrete steps.

Getting help in Virginia

Loclis lists DPOR-licensed concrete businesses with their licence number and class. Look up concrete contractors in Blacksburg, browse slab lifting and leveling or sidewalk and step contractors, or see all concrete and hardscaping answers.

Describe your steps once and licensed local concrete businesses quote the repair.