A sinking or sloping concrete stairway is a common structural issue that can compromise both the safety and aesthetic appeal of your property. Whether the soil underneath has settled or washed away, leaving the steps tilted to one side, leveling the concrete can often save you the time and expense of a full demolition and replacement. Lifting heavy concrete components requires a careful approach, an understanding of the hidden structure, and patience.
Understanding Concrete Stair Construction
Before attempting to lift any concrete slab, you must evaluate how the stairs were originally constructed. Stairs are typically poured in a few different ways, which directly impacts their structural integrity during the lifting process. Some stairs consist of separate concrete components, such as a bottom step resting independently against a larger concrete deck. In these cases, you must be incredibly careful, as lifting one section without the other can cause immediate cracking at the joint.
More commonly, residential stairs are poured as a single monolithic unit. The strength of this single unit relies heavily on whether steel reinforcement, or rebar, was installed during the initial pour. Rebar acts as the structural skeleton of the concrete. If the stairs contain an adequate rebar grid, they will likely have the tensile strength required to withstand the lifting process without breaking.
If the concrete is unreinforced, attempting to raise one side can easily snap the entire structure in half. Furthermore, many poured concrete steps are hollow underneath or filled with a core of gravel and soil. You will only be able to backfill the accessible perimeter once the stairs are lifted, which can result in a slightly hollow sound when walking on them later.
The Jacking Process And Dealing With Soil Suction
To begin the leveling process, you need to create an access trench along the sunken side of the stairway. By digging a strategic trench underneath the edge, you can position heavy-duty equipment like a hydraulic jack or a screw jack. It is highly recommended to place your jack on top of a wide, solid wooden block to distribute the heavy load and prevent the jack from simply driving itself deeper into the dirt.
As you begin to apply upward pressure, you might find that the stairway refuses to budge. Do not force it. Heavy concrete structures resting on damp earth often develop a strong suction effect against the soil. If you continue to aggressively pump the jack, you risk cracking the concrete or blowing out the soil beneath your jack base. Instead, apply firm, moderate pressure and simply walk away. Allow the structure to sit under tension for anywhere from fifteen minutes to an hour. Over time, the continuous pressure will slowly break the suction, and the stairs will often pop upward on their own.
Backfilling And Allowing For Settlement
Once the stairway breaks free from the soil, continue to slowly raise it to your desired height. However, experienced contractors know that newly introduced backfill material will inevitably compress. Therefore, it is wise to lift the concrete slightly higher than your final target elevation, usually by a quarter of an inch to three-eighths of an inch.
Pack your chosen backfill material tightly underneath the raised edges of the concrete. Rather than filling every single hole immediately, leave the trench partially open for a couple of weeks to observe how the structure settles back into place. If the stairs settle perfectly level, you can finish backfilling the landscape. If the concrete cracks extensively during any part of this process or simply crumbles due to a lack of internal reinforcement, the structure has failed, and full replacement will be necessary.
Three Key Tips For Lifting Concrete Stairs
Respect The Suction Effect: Never force a stubborn concrete slab. Apply moderate jack pressure and wait for the concrete to naturally release its suction from the soil to prevent catastrophic cracking.
Over-Lift For Settlement: Always raise the sloping end slightly higher than perfectly level, ideally by about a quarter of an inch. This accounts for the natural compression of the new backfill dirt or gravel once the weight of the stairs is lowered back down.
Account For Unreinforced Concrete: If you suspect your older stairs lack interior steel rebar, proceed with extreme caution. Unreinforced slabs have incredibly low tensile strength and are highly susceptible to snapping under uneven jacking pressure.
Frequently Asked Questions
Do I Need A Building Permit To Repair Or Lift Concrete Stairs?
Depending on the scope of your work, a permit may be required by your local municipality. According to the International Residential Code, minor cosmetic repairs and leveling often do not require a permit. However, if the lifting process fails and you are forced to demolish and pour a brand new set of concrete stairs, a building permit and subsequent inspections are almost universally required to ensure the new structure meets modern safety standards.
What Is The Maximum Allowable Slope For Exterior Concrete Stairs?
While a severe slope is obvious, even minor settling can violate safety codes. The International Building Code and International Residential Code state that the maximum allowable cross slope for stair treads is two percent. This slight slope is required to shed rainwater and prevent ice buildup, but anything exceeding this two percent threshold becomes a tripping and slipping hazard that must be leveled.
What Is The Best Material To Backfill Underneath Lifted Concrete Steps?
While you can reuse native soil for the perimeter, the primary void created by lifting the stairs should be filled with a stable, non-expansive material. Crushed gravel or crushed stone is excellent because it compacts well and allows for proper water drainage. Alternatively, professional concrete lifting companies utilize high-density structural polyurethane foam, which is injected under the slab to precisely raise it and cure into a waterproof, permanent base that will not wash away over time.
