Manholes, concrete inlet and outlet structures

General Requirements 6.10.1

The contractor must excavate, supply materials and construct all manholes in accordance with the Drawings, subject to the tolerances specified in Tolerances. N25 Grade concrete must be used, unless otherwise shown on the Drawings.

Outside formwork must be used where the excavation exceeds the tolerances specified.

An outside formwork must be used when forming the shaft of the manhole. No slip forming will be permitted.

The contractor is permitted to use precast concrete manholes conforming to AS 4198-1994 on the basis all of the requirements of this section are met.

Tolerances 6.10.2

The contractor must construct manholes which meet the following requirements:

  • the invert levels of inlet and outlet pipes must be within the tolerances for pipe laying specified in Pipe-laying tolerances - backfall across the manhole channel won't be permitted
  • the level of the cover must be within five millimetres of the level specified on the Drawings or as directed by the Superintendent

  • variations of manhole dimensions mustn't exceed the limits specified in AS 3600-2009.

Tolerances for precast manholes shall conform with AS 4198-1994.

Surface finish of manhole walls 6.10.3

The surface finish of all manhole walls must be Class 2 or better, as described in AS 3610-1995. If the Contractor fails to achieve the required finish, the concrete must be repaired in accordance with the requirements of AS 3600-2009 or as directed by the Superintendent. If directed by the superintendent, the manhole must be rebuilt at the contractors expense. Bagged mortar mustn't be applied to manhole walls.

Manhole stepirons and ladders 6.10.4

Stepirons and ladders must conform with AS 1657-1992 and be located and fixed in manholes in accordance with the Drawings.

Manhole access stepirons must be cast in situ. Stepirons used for other purposes may be installed in drilled holes using a dry packed mortar or epoxy compound.

Manhole covers

Manhole covers must conform with AS 3996-2006 and be Heavy-duty Gatic Type BV or equivalent and fixed flush with the pavement or finished surface level, or in accordance the Drawings and Tolerances.

The Contractor must prevent distortion of cast iron frames during fixing and replace any distorted cover or frame. Cast iron covers must be filled with N25 Grade concrete. The identification, cover locating marks and numbering pad must be left exposed.

The covers and frames must be cleaned and greased after completion of the section of the Works.


Where site conditions require the use of weepholes, they shall be placed in accordance with Drawing 7251/8/403. The holes must be a minimum diameter of 38 millimetre. The outlets must be clean and flush with the outer face of the structure.

Weephole formwork must be set in place before concrete is poured. Hollow weephole formwork must be temporarily filled and covered with bituminous paper or plastic film before pouring to prevent concrete entering the cavity.

Placement of bolts and stepirons 6.10.5

All bolts must be placed in the formwork before pouring the concrete. Care must be taken to ensure stepirons remain in place and are properly aligned after pouring.

Bellmouth inlets to pipes 6.10.6

The surface finish of bellmouths must be Class 1 or better.

Public warning signs 6.10.7

The contractor must supply and install warning signs on the structures above the pipe with approved bolts. The signs must conform to the size, layout and print type in accordance with AS 1319-1994. 


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