Medmenham Residence
A double-height, free-spanning helical post-tensioned staircase, gravity-defying structural engineering realised in natural stone with absolute precision.
Project Details
Commissioned to deliver a central feature of absolute grandeur, AFJONES designed and constructed a spectacular double-height, free-spanning helical staircase.
Originally conceived in glass and timber, the client ultimately chose the timeless permanence of natural stone. This project merges advanced structural engineering with craftsmanship, resulting in a gravity-defying architectural sculpture.
Design, Engineering & Material Science
Specifying for
Strength
Driven by structural calculations and client requirements, AFJONES specified a hard Portuguese limestone from the Fatima region. Chosen for its uniformity and high compressive strength, the raw blocks were meticulously selected to be entirely free from natural vents or soft beds.
Two flights — 22 and 24 treads, each rotate 270–280 degrees in a double-height void without wall supports. A "gull-wing" tread soffit was designed to balance structural mass with visual slenderness.
Structural Engineering
Calculating
the Helix
Working with structural engineers Price & Myers, AFJONES used heat mapping and predictive bending diagrams to calculate the required compressive stress. Nine months prior to installation, a full-scale mock-up was built to test bespoke solutions including proprietary rubber gaskets.
Comparing real deflection data against structural models guaranteed absolute certainty before a single stone was installed on site.
Because these structures are unstable during intermediate phases, installation required meticulous sequencing. Every tread was fixed under the direct supervision of AFJONES engineers, with each step post-tensioned before the next could be placed.
Precision Installation
Masterminding
the Build
The result is a staircase that appears to float, its structural logic completely concealed within the elegance of the form.
The result is a staircase that appears to float, its structural logic completely concealed within the elegance of the form.
Gallery
Medmenham Private Residence
Gravity-Defying Form
A Staircase That
Appears to Float
The completed staircase is a testament to what becomes possible when engineering ambition and stonemasonry craft are brought together. Slender treads in Portuguese limestone appear suspended in space, their structural logic hidden within the precision of the construction.
AFJONES involvement from structural design through installation ensured every decision, material, geometry, sequencing, served both the engineering requirements and the visual ambition of the project.
A gravity-defying helical staircase in natural stone — the art and science of stonemasonry at its most ambitious.
AFJONES involvement from specification through installation, including a full-scale mock-up nine months before build, ensured that structural certainty and architectural beauty were achieved simultaneously.
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