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Students Zone

Case Study Ten

Upper floors and stairs

Formation of suspended timber floors

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Floor joists may be built directly into the inner leaf of the external walls. Where they are supported by internal walls they are placed directly onto the wall as shown. It is often necessary to use bricks to adjust the height of the floor as blocks are too large. This can be clearly seen here.

Joists may also be supported using galvanised steel joist hangers. These are built into the walls as work proceeds. The joists can then be positioned later, thus speeding up the construction process. The metal straps that can be seen running along the sides of the joists are lateral restraint straps. These ensure that the external walls are tied to the upper floor to resist lateral loads.

	Here we see the bracing that is provided to the floor at mid-span to resist twisting of the joists. The opening created for the stairs is created by the use of trimmed, trimmer and trimming joists. The connections are made using joist hangers.

Stairs

Here we see a typical timber stair installed in a new dwelling. The nature of the stair construction is clearly visible with the various braces, wedges and glue blocks seen from beneath. Note that the string of the stair is propped above the floor slab at a level that coincides with the finished floor level of the ground floor. The structural performance of the stair relies on the string spanning from top to bottom. It is not fixed to the adjacent wall.