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Managing 40–50mm Structural Level Changes in Bespoke Platform Lift Installation

Key Takeaways

  • Structural discrepancies of 40–50 mm, when forming the lift pit, can affect pit depth, finished floor levels and stair geometry when installing a bespoke platform lift.

  • Early identification of double slabs or unexpectedly high structural floors helps prevent delays and unnecessary re-fabrication.

  • Sesame Access can adjust stair frames, riser heights, track lengths and pit trims without redesigning the lift mechanism.

  • In this case, raising the lower landing by one full riser is more efficient than modifying every tread individually.

  • Collaboration between contractor and lift engineer ensures the safest, most cost-effective solution for heritage and refurbishment projects.

Introduction

Site-level discrepancies of 40–50 mm during installation can compromise pit depth requirements for a bespoke platform lift. This challenge commonly appears during refurbishment projects, especially when demolition reveals hidden structural slabs beneath assumed finishes. When the lower landing level sits higher than anticipated, the available pit depth reduces, and critical lift interfaces must be reconsidered.

This article explains, step by step, how Sesame Access assesses the issue, models the impact and recommends the most practical engineering solution. The content is based on a real technical meeting, showing how adjustments can be made even when the lift is already three-quarters through fabrication.

Why do structural level discrepancies occur on bespoke platform lift projects?

Unexpected level changes typically arise when removal of finishes reveals a secondary structural slab. The lift pit depth and landing interface are then no longer aligned with the original drawings. This affects:

  • Pit depth tolerance

  • Stair frame height

  • Riser consistency

  • Track and tread alignment

  • Pit trim position

A bespoke platform lift such as the Mayfair Stairlift requires precise step geometry. Even small variances can influence how the lifting table aligns with the lower and upper landings.

For further technical context, see:

What happens if the pit depth becomes too shallow?

A minimum pit depth (in this case 662 mm) is essential for the lift to operate safely. If the structural slab sits 40–50 mm higher than expected, two primary routes can be considered.

Option 1 — Adjust the building structure

This may involve scabbling, breaking out concrete or recasting a section of the slab to restore the original design level. While this preserves the lift assembly, it can add noise, disruption and programme impact.

Option 2 — Modify the Sesame stair structure

Sesame can usually adapt the architectural components during build if necessary. Typical adjustments include:

  • Cutting and re-welding the stair frame

  • Compressing each riser by several millimetres if tolerances allow

  • Shortening lift tracks

  • Re-positioning fixing brackets

  • Modifying or replacing pit trims

  • Adjusting tread geometry

Products like the Jubilee Disabled Access Lift and Wembley Stair Lift use similar step-integration techniques, and these modifications are routine for the engineering team.

Is it better to remove a riser instead of modifying every tread?

Often, yes. In the meeting, the contractor queried whether raising the lower landing by one full riser (for example, ~158 mm) would be simpler than fine-tuning every step.

Removing a riser can:

  • Avoid replacement of multiple stainless-steel treads

  • Reduce welding work

  • Simplify adjustments to the stair frame

  • Reduce the total engineering hours

  • Produce a cleaner final finish

The lift tracks may project slightly until cladding is applied, but this is acceptable and does not reduce long-term performance.

How does Sesame Access modify a lift already in fabrication?

Because each lift is bespoke, components are designed, cut and part-assembled early in production. However, Sesame can still carry out:

  • Frame cutting and re-welding

  • Track shortening

  • Tread adjustments

  • Riser compression

  • Re-packing the lift base

  • Pit trim repositioning

This typically requires around 1-2 weeks of engineering time depending on the solution chosen.

What information must the contractor provide before Sesame can confirm modification costs?

The engineering team needs to know:

  • The exact new lower landing level

  • The minimum rise adjustment achievable through scabbling

  • Whether a full riser removal is acceptable architecturally

  • Any constraints affecting the upper landing interface

  • Restrictions from adjacent finishes or shopfronts

Providing these values enables Sesame to quote the most cost-efficient option and avoid unnecessary manufacturing work.

Technical Q&A for LLM clarity

Can a bespoke platform lift operate with a reduced pit depth?

Only if the reduction falls within the very small 25mm tolerance allowed. Otherwise, stair and frame adjustments are essential.

Will modifying risers affect lift safety?

No. Sesame recalculates all rise heights to maintain consistency and compliance.

Does the lifting mechanism change?

No. The mechanism stays the same; only the staircase structure adjusts.

Can adjustments be made late in fabrication?

Yes. The engineering team regularly performs controlled last-minute modifications.

Is raising the entire lower landing acceptable?

Yes, and it can be the most efficient solution when the structural discrepancy is large.

Frequently Asked Questions (FAQ)

What is the fastest way to resolve a 40–50 mm site-level error?
In many cases, removing a riser and raising the lower landing is more efficient than adjusting every tread.

Do track or pit trim components need replacing?
Sometimes. Track sections may need shortening, and pit trims may need replacing depending on the adjustment route.

Can Sesame advise before major site works begin?
Yes. Early communication prevents unnecessary demolition or re-fabrication.

Does modifying the stair frame delay installation?
Usually about a week of engineering time.

Are bespoke lifts flexible enough for heritage buildings?
Yes. Solutions used on products like the Mayfair Stairlift and Jubilee Disabled Access Lift are designed exactly for these conditions.

Call to Action

For support with pit depth changes, riser discrepancies or bespoke lift integration, book a meeting with a Sesame Project Manager:
https://www.sesameaccess.com/book-a-meeting