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How to Conduct a Technical Pit Inspection for a Hidden Wheelchair Lift Installation

Key Takeaways

  • A technical pit inspection prevents costly alignment and structural errors before installation begins.
  • Hidden wheelchair lifts require exceptionally precise beam, riser, and pit measurements.
  • Engineers use verification drawings, laser measurements, and structural exposure checks to confirm accuracy.
  • Early detection of inconsistencies avoids rework, delays, and on-site safety issues.
  • Proper inspection ensures that hidden lifts operate smoothly without affecting surrounding architecture.

Introduction A hidden wheelchair lift is a platform lift that disappears seamlessly into a staircase or landing, preserving the architectural integrity of the building. These lifts must fit perfectly within their structural surroundings, meaning every millimetre of the pit must match the engineering drawings. A technical pit inspection is the stage where engineers verify that the site is prepared correctly before lift manufacturing or installation begins. It protects the project from unexpected clashes, misaligned beams, structural inaccuracies, and delivery complications. For further general installation guidance, you can refer to the Lift-installation, as well as the Sesame Access Global Installs article showing how these engineering principles apply worldwide.

What Is a Technical Pit Inspection? A technical pit inspection is an on-site engineering review that checks whether the builder’s preparation aligns with the lift design. Because hidden lifts rely on tightly controlled tolerances, the inspection covers everything from beam positions to riser offsets and temporary support requirements.

Why Hidden Lifts Require Precise Verification Hidden lifts like the Kensington Stairlift, Westminster Equality Act Lift, and Knightsbridge Stair Lift rely on precise integration between structural steel, stair geometry, and gate assemblies. Even a 20 mm deviation can affect:

  • gate swing
  • lift travel path
  • ability to deliver the lift into the building
  • the alignment of risers and gates
  • the load distribution of the surrounding floor

This is why on-site verification is essential before the lift is shipped.

Numbered Steps: How Engineers Conduct a Technical Pit Inspection

1. Confirm Datum Lines and Reference Points Engineers begin by locating the site’s primary datums. These are compared against the lift drawings to establish true reference positions for:

  • centre lines
  • pit boundaries
  • upper landing finish floor level
  • beam edges A laser level is then used to recreate the drawing conditions on site.

2. Verify Beam Positions and Alignment Beams must be measured at multiple exposed points. Engineers check:

  • horizontal offset from the datum
  • vertical twist and level change
  • beam-to-beam spacing
  • whether concrete or fireproofing is concealing the true steel

If a beam is 20–90 mm out of position, the lift model must be updated before manufacturing can continue.

3. Measure Pit Depth Accurately Pit depth is taken from the upper landing finish floor level down to the top of the pit steel. Depth variations can affect:

  • lift resting height
  • flush integration
  • packing requirements Even small discrepancies must be recorded and fed back into the installation plan.

4. Check Riser Alignment and Step Geometry Risers often differ between drawing and site conditions. Engineers check:

  • whether left and right risers align
  • the actual distance between them
  • whether future cladding or bedding layers will alter these measurements If the risers are offset by 50–100 mm, gate alignment and usable entry space must be reconsidered.

5. Confirm Pit Boundary Steelwork Pit steel frames or box sections are checked for:

  • correct position
  • correct level
  • correct distance from the riser or beam
  • compatibility with the lift’s A-frame and stabilising brackets

If the pit boundary is misaligned, channel sections or spacers may be recommended.

6. Assess Temporary Support Requirements Many sites include suspended floors or incomplete mezzanine levels. Engineers check:

  • whether temporary props are required
  • whether the floor can support a two-tonne lift
  • whether access doors must be removed for delivery
  • whether road closures or specialist handling equipment are required

This step avoids structural damage and ensures project safety.

7. Record All Measurements and Map Them Into the Lift Model After the inspection, engineers adjust the 3D model with:

  • beam adjustments
  • pit offsets
  • riser changes
  • gate assembly corrections
  • temporary support notes
  • impacts to delivery routes

This updated model becomes the final pre-manufacture reference.

Common Issues Found During Pit Inspections Pit inspections frequently uncover issues such as:

  • misaligned box sections
  • risers offset by unplanned cladding thickness
  • beam positions differing from drawings
  • insufficient structural support under temporary floors
  • incomplete concrete removals
  • gate swing paths blocked by unexpected steelwork Identifying these issues early prevents installation delays.

Typical Applications and Related Products A technical pit inspection is required for all hidden lifts, including:

Each of these lift types relies on precise integration with existing architectural features.

Frequently Asked Questions How long does a pit inspection take? A typical inspection lasts 1–3 hours depending on site accessibility, steel exposure, and the number of structural elements needing verification.

What tools do engineers use during the inspection? Laser levels, digital tape measures, straight edges, and drawing overlays are common. For hidden steelwork, partial concrete removal may be requested.

Can the lift still be installed if the pit is not perfect? Yes. Most issues can be resolved using spacers, revised steelwork, or changes to gate assemblies. Critical issues are flagged early to avoid costly rework.

Why can’t the pit trim be fitted after the lift? There is not enough space beneath a suspended lift to safely fit trims. They must be installed before the lift arrives on site.

Do all hidden lifts require a technical pit inspection? Yes. It is mandatory for all Sesame hidden wheelchair lift systems to ensure the lift integrates properly with the building.

What happens if the floor cannot support the lift delivery? Temporary acrow props or structural steel may be recommended to protect the building during delivery and installation.

Call to Action If you would like expert guidance for your upcoming lift project, book a Teams meeting with one of our Project Managers using our online meeting scheduler.