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| A TYPICAL STAIR LAYOUT WOULD CONSIST OF THE FOLLOWING
COMPONENTS: |
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Reinforced Precast Stringers |
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Precast Landing Slabs |
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Stingers are made up in riser heights 166mm, 170mm and 184mm, with a
250mm, 280mm, 300mm tread. All stringers are 150mm wide and the number of
risers per stringer vary from 3 to a maximum of 12.
Stringers are designed to carry brick balustrade walls if required, it is
therefore possible to design stairs with the minimum of restriction as far as
supporting walls or columns are concerned.
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Midway landings and walkways can be supplied if required. As a rule Precast
Staircases pre-stressed T-beams will be used for these applications.
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Reinforced Precast Landing
Beams |
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Reinforcing Bar / General |
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Landing beams used with the stringers are the key to obtaining various
configurations of stairs i.e. dogleg stairs, quarter turn stairs and open
well stairs, The maximum span allowed for a standard landing beam is
3500mm carrying a full load of stringers. All landing beams are cut to size
prior to installation.
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After erection of the components a reinforcing bar is placed into a hole in the
stringers and grouted in through the aperture provided on the treads. Care must
be taken to ensure that the reinforcing bar runs through the full width of the
stair. The grout mixture should be made up of relatively dry river sand and
cement. If all the voids, on the appropriate tread, are properly grouted to
capacity it will result in a monolithic structure which in turn will prevent
micro movement of the stringers to ensure a crack free finish on the stair.
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All conventional finishes can be applied to treads and risers. The following
suggestions will ensure a maintenance free stair:
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Treads and Risers |
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If the stair has been installed with minimum adjustment to levels it can be
tiled with ceramic tiles without any additional screeding, otherwise a 15 /
20mm screed is recommended.
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If the stair is open to the elements, it is advisable to use a waterproofing
membrane on the treads and risers before final finishing of the stair.
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In the case of vinyl or carpeting of the stairs, we recommend a 15 / 20mm
screed on the treads and risers before final finishing.
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The surface finish of the components are such that a substantial mechanical
bond is obtained by tile adhesives or cementitious screeds.
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Midway landings and walkways can be supplied if required.
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Landing Slabs |
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A 30 - 50mm cementitious topping is required on all landing slabs prior to
final finishing. |
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Soffits of Stringers and
Landing Slabs |
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Depending on the required aesthetics and the location of the stairs, the soffit
finish can vary between a 12mm plaster, a cementitious tyrolean, a sprayon
textured paint finish or the stair can be left as is.
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Balustrades |
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Brick balustrades can be built directly on the precast stringers in the
conventional manner.
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Steel, wood or aluminum balustrades can be fixed into the edge stringer by
drilling a hole to suit and filling the aperture with a non-shrink grouting
material.
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The same can be fixed onto the side of the edge stringer by means of drilling
holes and using expanding bolts or screws.
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Stringers and landing beams are designed to cater for 5Kn/m2 superimposed live
load, which also provides adequate reinforcement for handling.
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Concrete Design Strength - 40Mpa |
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Steel Reinforcing - Reinforcements as per sketches below |
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Landing beams are positioned on load bearing supports, set out to the correct
levels and positions, in accordance with the layout drawings.
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Stringers are lifted into position on the bearing nibs of the landing beams and
placed side by side to make up the required stair flight width.
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When a required flight width is not a multiple of the 150mm stringer width, a
makeup strip may be formed between two or more convenient stringers or the edge
stringer and the wall and filled solid with in-situ concrete.
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Landing slabs are now placed into position.
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When all components have been adjusted and aligned, a reinforcing bar is
introduced into the hole on the side of the stringers, midflight, and grouted
solid through the semicircular aperture in the tread above.
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A dry mix of river sand and cement grout is then thoroughly brushed into all
the gaps on the surface of the risers, treads and landing slabs.
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