When designing precast stairs, special consideration needs to be taken when locating the units on to a suspended floor. Often, ground floors are of beam and block construction. These can be procured through the groundworkers package and therefore not necessarily designed and supplied by same precast company as the stairs. Special attention to collaborate in design at an early stage is vital!
One of the main issues we come across in the precast industry is the note on architect and engineers’ drawings ‘design by specialist precast contractor’.
Common problems
- Stairs do not locate correctly on beams
- Correct stair loading not considered in beam and block design.
- Calculations not provided although normally worst-case scenario for loadings.
Solutions
- Design Collaboration
- Single source provider
Design collaboration is key throughout a project. Combining the necessary information and ensuring each element links seamlessly on site is a big task for principal designers and main contractors. With multiple sub-contractors and varying levels of design input, communication is paramount.
In many cases, this indicates little consideration for the orientation and supports for the precast units. In these cases, often, additional supports or enhanced precast products are likely to be required.
During the purchasing and contracting stage, we would always suggest you utilize one precast supplier for each element. This gives you much easier communication and collaboration but also allows the precast designer to ensure cohesion between each product.
Due to lead times, many stairs are designed after the ground floor has been delivered and installed. The beam and block may well have not allowed for a precast stair or only made an assumed allowance for the dead load to be applied. Therefore, little or no design calculations have been carried out to ascertain the validity of the supporting structure.
The staircase needs to be designed to ascertain the location and loading to be applied. Then the ground floor beams can be designed, and calculations assessed. If the stair loadings cannot be supported, it may be possible to increase beam specification or introduce additional substructure support.
In any case, the sooner this is ascertained, the sooner the potential issue can be eliminated.
PSS provide a single source solution to your precast requirements. We are dedicated to offering value in collaboration, design and service.