The standard Utilihab stairs have the conventional staircase elements of treads, side-supporting stringers, risers, and hand rails and are designed to fit within a single panel floor grid space and so are normally 1m or 2050mm wide. The standard stairs do not use winding steps and rely on platforms for turns. Stringers are based on 50mm profiles supporting treads from the sides along two or more slots and are attached between the side face of Primary horizontal beams or the top face of main floor joists reinforced with a spacer or a special extra-wide spacer with side-tightened tension plugs between main floor joists. Normally, at least one side of the stairs will run parallel to Primary framing. The stringers with basic stairs are exposed, running over the surface of wall panels and optionally bolted along flush Secondary frame members. The handrail likewise mounts to the Secondary frame members. If the opposite side of the staircase is ‘open’ it then uses 50mm posts and balusters over the floor deck joists and spacers. This allows the standard wall panels to slip behind the stringers, needing no modification, and allows the standard partition panels to easily conceal a staircase.
The most basic staircase uses all off-the-shelf profile components including ready-made tread profiles attached by tension plugs tightened from beneath. These are open stairs without riser plates, though optional alloy risers may be added by attachment of ‘L’ profile shapes. Nosing along the edge of the tread is accommodated with snap-in wear strips or bumpers where it is not formed into the tread profile. These wear strips or slot cover strips may also be used to cover exposed slots along the stringers as well.
For a more domestic appearance, A routed pre-finished wood cover plate is added over the alloy stringers and treads are made of pre-finished wood with routed channels to host a pair of thinner supporting alloy profiles. Hand rails and Secondary framing balusters may likewise employ a channeled wood finishing cover over a smaller (20mm-25mm) profile while lighter balusters may use pre-finished wood shapes attached by counter-sunk bolts or pins. For closed stairs, the treads are designed to accommodate pre-finished riser plates fitted with small alloy angles to bolt to the back and underside of the concealed tread profiles.
A concealed or flush stringer approach is achieved by mounting the stringers behind or flush to specially modified wall panels and running them right along the planes of the Primary and Secondary framing where they attach by angles to available profile slots. Secondary frame members are modified to mount in-line with the stringers. A slightly wider form of the wood covered tread is used and attaches to the stringers through holes in the wall panels or along and through a flush mounted wood cover plate.
Under-slung stringer stairs offer yet another options with potentially greater simplicity in construction, at the compromise of some heavier components. This form of stairs employs stringers that support treads from beneath rather than from the sides and is particularly attractive where open treads are used. One or more Primary frame profile (usually 100x200mm or larger) stringer-beams are mounted between the side faces of Primary frame horizontal beams or main floor joists. At the base of the stairs, the beams descend below floor panel level and so specially modified floor panels must be made to conceal them. The treads -either profile based or pre-finished wood over concealed profiles, attach to the top of the stringer beam on angles, consoles, or specially cut profile wedges. Handrails, where necessary, are independent of the stringers and would be mounted to Secondary wall studs or to balusters and studs (optionally wood covered) along the treads. Normally, these forms of stairs use open tread designs but where this is used as a simpler approach to conventional staircases the same pre-finished riser plates can be used. While this is a much simpler stair structure and works well at avoiding modification to standard wall panels, it is more dependent upon integration with Primary framing members and, where this is not directly available, may require the stringer beams be supported by their own foundation footings or the floor joists/spacers they interface to be reinforced.