This week’s Finer Details of Interior Stone is about the key differences between a traditional cantilever stone staircases and natural stone post-tensioned staircases. Understanding the differences between the two is more than knowing two types of construction: accounting for the differing project and planning needs for each is essential.
Cantilevered vs. Post-Tensioned Staircases
The elegant shape of a free-standing post-tensioned staircase in natural stone.
The earliest known cantilevered staircase in England is the Inigo Jones Tulip Stairs at Queen’s House, Greenwich (1635) and the elegance of his architectural style and construction technique remains a benchmark of elegance in staircase design. Whilst post-tensioned stone staircases have similar building blocks (i.e. formed from interlocking solid treads), they are structurally completely different and require an even higher level of sophistication in design and construction techniques. However, free-standing post-tensioned staircase will create an astonishing and elegant centre piece for any project, more than additional input of planning and design required.
Whilst a traditional cantilever staircase can be progressively built and remains in a stable condition, firmly attached to the wall and gaining integrity with each tread added, a post-tensioned staircase requires temporary supports in all intermediate construction states. Until it’s fully complete and tensioned up, this temporary support system for a post-tensioned staircase needs careful planning, building and unbuilding through the project process.
Natural Stone Post-Tensioned Staircases – technical detail
The technical aspects of post-tensioned staircases demand the development of specific expertise from the specialist stonemason, including: 3D geometry generation; tread & hole trajectory drilling; strand curvature and loading sequence; steel anchorages and stone enclosures; specialist mortars and grouts; load testing and deflection monitoring; support frame technology & options – and many other nuances in the practical achievement of these projects.
Post-Tensioned Staircase Specialists
A design for a statement-piece, two-level natural stone post-tensioned staircase.
As a result of these technical aspects, it is even more important that the specialist stonemason team (such as AF Jones Stonemasons) is fully integrated into the Project & Design & Contracting overall team from the very earliest concept design stage onwards, including the careful planning of logistics and site-sequencing to completion.
At AF Jones we take responsibility for the design integrity as well as complete manufacture and installation works as part of our service for post-tensioned staircase projects. By integrating with the Client, Contractor as well as Design Team, we joint the dots across the project team and bring the project to life, from inception right through to after care.
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