Leveling and Plumbing Steel Stair Stringers During Installation

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Leveling and plumbing steel stair stringers means setting each stringer vertically true and horizontally level before anything is fixed permanently. Work from a reference line, shim and adjust at the anchor points, and check both stringers against each other so the treads and risers line up across the full run.

Why stringer alignment matters

The stringers carry the whole staircase, so any error in their position shows up in every tread and riser above it. A stringer that leans or sits out of level can make treads rock, risers vary in height and handrails fail to line up along the run.

Accurate alignment also protects the finish. Glass balustrades, wall-mounted handrails and tread nosings all depend on the stringers being true, so correcting them early saves rework later.

Preparing before you set the stringers

Start by confirming the opening, the landing levels and the reference lines from the drawings. Check that the floor or landing structure is level and that the anchor locations are clearly marked on both walls or beams.

Verify the drawing dimensions against the site
Mark a level reference line at the top and bottom landings
Clear the path and confirm the lifting and positioning plan
Have shims, wedges, a spirit level and a plumb line ready

Setting the stringer level

Position the stringer on its supports and check it along its length with a long spirit level or a laser. Adjust the packing under the base plate or bearing point until the stringer runs at the correct slope and matches the reference line at the landing.

Do not force the stringer into place with fixings. Packing should carry the load so that the stringer is supported, not pulled into position by bolts that may later loosen.

Plumbing the stringer vertically

Plumbing means checking that the stringer is vertical or at the correct angle to the wall it fixes to. Use a plumb line or a digital level on the face of the stringer, and check at the top, middle and bottom.

Checks to make

Compare the readings at each anchor point. If one end reads differently from the other, adjust the anchors or shims until the stringer is true before tightening any fixing.

Aligning the two stringers together

Once both stringers are set, measure the distance between them at several points along the run. The width should be consistent from top to bottom, and the diagonals across the staircase should match, which confirms the frame is square.

Check that the tread positions on each stringer line up at the same height. Small differences here can be accepted only if the design allows adjustment at the tread connections.

Fixing and final checks

When the stringers are true, fix them permanently through the anchor plates into the structure, using the specified fixings. Tighten evenly and recheck the level and plumb after tightening, since movement can occur.

Finally, confirm the handrail line, the landing connections and the first and last risers. Record your checks so the finish trades can rely on the alignment.

Frequently asked questions

What tools do I need for leveling steel stringers?

A long spirit level, a plumb line or digital level, a laser if available, a tape measure, and shims or wedges. A string line helps confirm the run is straight.

Should I level the stringer before or after fixing it?

Level and plumb it first, using packing and temporary support, then fix it permanently. Re-check after tightening because the stringer can shift slightly.

Can packing be used to correct a stringer that is out of level?

Yes, shims and packing are the usual way to correct small differences at the support points. The packing should be solid and properly bearing, not loose or stacked haphazardly.

How do I know the stair alignment is correct?

Check that the stringers are level and plumb, the width is consistent along the run, the diagonals match and the risers are uniform. Exact tolerances are confirmed with the engineer.

Common mistakes to avoid

A common error is fixing the stringer tight before it is level, which locks in misalignment and makes later correction difficult. Another is trusting one reference point without checking the full length of the run.

Our recommendation

Take readings at the top, middle and bottom of each stringer and recheck both sides together before any permanent fixing. Confirm any tolerances or fixing details with the project engineer before finishing.

Summary

Level and plumb each steel stringer against a reference line, adjust with solid packing, and confirm the two stringers match before fixing them permanently.

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