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Builders work holes within the riser

Scenario 1 – Single Builderswork Hole within Riser- Criteria for Maximum Hole Size

G must be greater than 300mm or greater than the half the width of the builders work hole.

I must be greater than 150mm or greater than half the depth of the builders work hole.

If a situation occurs where it is not possible for enough material to be left in place once services holes have been cut, entirely remove the section shaded in yellow OR

If this results in the width of I being less than 150mm unistrut (designed by a structural engineer) should be installed to support dura tread from underneath.

Scenario 2 – Multiple Builderswork Holes & Minimum Spacing Requirements

Minimum Value of Left Material:

The minimum amount of dura tread left between two builders work holes must be greater than 100mm. If the residual amount of dura tread left after cutting the holes is less than 100mm, it should be removed (shaded area above).

Scenario 3 – Multiple Builders Work Holes where Additional Support is Required

This situation has 2 problems:

The yellow shaded areas are less that 100mm wide and therefore they are not safe to stand on.

If the areas are removed they will create a cantilever situation and areas F & G will fall out.

Unistrut/ steel underneath the dura tread grating (designed by a structural engineer) bracketed onto riser walls will allow Scenario 3 to be achieved safely and the yellow shaded areas can be left in place (see scenario 3A.)

Scenario 3A – Arrangement of Additional Support

Scenario 4 – Support of Dura Tread Riser Panel Joints

Risers greater than 1220mm wide:

When a riser is wider than the panel width a supporting beam (designed by a structural engineer) must be fixed underneath where the panels join. Bearing surface must have an overall width of 100mm. This will allow enough flange width to fix down through.

In the above case, position AA or BB can be used for the reinforcement beam. Position AA in this case is preferable.

Scenario 5 – Minimum Spacing Between Adjacent Builders Work Holes

Material in between small services holes that is less than 100mm wide should be removed, unless the holes are less than 60mm diameter.

Scenario 6 – Arrangement of Multiple Builderswork Holes Requiring Additional Support

Where a large number of cut outs are required in a riser, a premade frame (designed by a structural engineer) should be supplied to support the Dura Tread This frame should be installed prior to any holes being cut out.

It may be easier to completely remove a larger area of Dura Tread (see scenario 8A) and barrier off.

Scenario 6 A