Cast in Place Buildings
We are often invited to provide precast stairs in cast in place structures to help the contractor avoid non-compliance of stair dimensions. Non-uniform riser heights and spalled or dished treads and nosings create tripping hazards and liability for building owners. Castcon’s precast stairs, factory-cast for quality assurance, are shipped to your site and set into place within your formwork with splice reinforcement already provided in the ends of each stair unit. All you have to do is pour your landings to the stairs.
Castcon Value Added
Castcon solves your code compliance problem with precast stairs that are compliant, not only to the applicable building code, but also to PCI MNL 116 tolerance regulations for structural precast concrete. Therefore, Castcon is able to produce a dimensionally accurate stair that can be set immediately into your cast in place structure. During construction, the contractor gains safe access to active construction areas without having to purchase temporary stairs. Precast can also be designed for blast resistance, extreme wind, seismic areas, moisture resistance, sound suppression, and high durability. Also, Castcon not only meets the code for fire resistance but can exceed it. Castcon stairs are the right choice for quick, easy erection and long term benefit.
Separate Stairs & Landings
The landings will be supported on the side walls of the tower. The support can be shelf angles, a casted-in ledge, or even an RVK (a tube steel within tube steel embedded device that extends into a hole in the cast in place wall. Within a cast in place structure, we feel the separate stair and landing design may be the most ideal because it offers more joints between pieces which means greater flexibility during the erection process. Greater flexibility means that you can allow for the difference of tolerances from a precast landing (which is much more stringent than cast in place tolerances) as compared to the tolerances of cast in place walls. Having more pieces in this situation may actually reduce erection time if the cast in place stair walls are out of tolerance (dimension). Castcon is able to ease the joints at the design stage, taking the propensity of this situation into consideration early so as not to slow down the building of the project.
Single Run Stairs
The single run stair design is for applications up to 12’-0” height floor-to-floor elevations. Castcon can design the stair to bear on the poured floor slab or have exposed rebar from the stair spliced directly into the floor slab that is to be poured. This design is an economical alternative, in that you can have two stairwells in one shaft, separated by a fire wall. We see this design most commonly in cities where the real estate is mostly “vertical” (see Carillon case study). Using precast will save the contractor time (erect a piece in 20 – 30 minutes) instead of one to two days of forming the stairs out of wood, pouring, curing, and disposing of form materials. Another savings, if coordinated properly, is not having to procure temporary stair systems for the job. Finally, precast stairs are a code-compliant, aesthetically pleasing alternative to cast in place stairs. The building code inspector should be pleased with code compliance in the cast in place stairwell, which is not always the case with other materials.
Half-Z Stair Design
This design is similar to an Open Zee except that it only has one integral landing (at either the head or the foot), hence the term “Half-Z”. This design would usually have integral mid-level landings that are supported at the mid-level end wall and rest on either a separate precast slab or possibly a cast in place slab. This design saves the erecting of a separate mid-level landing (since it is integral to the stair). This design will cause a joint to be visible in the middle of the mid level landing. Should the architect or owner not wish to see the joint, Castcon can offer a rake finish recess (usually 2” recess on top of landings with rough rake-like finish) so that a cast in place topping can be poured over the joint for a seamless look.
Open Zee
An Open Zee stair design can also be used in a cast in place structure (this type of stair has an integral head and foot landing). The head landing of one stair will be connected to the foot of an ascending stair, which means only two pieces per level need to be erected. The landings need to be supported off the end walls (whether by shelf angle, cast ledge, etc.). As noted with the Half-Z stair design, there will be a joint visible in the middle of the landings (which acceptable in most applications). However, Castcon can provide a 2” recess rake finish for final topping in the field, should a seamless look be desired.