Cover, seating, reducing and landing slabs

Cover Slabs

AG manufacture Type 2 heavy duty concrete cover slabs suitable for manhole units.

They come in a range of dimensions, however non-standard  can be designed and supplied to order. Cover slabs with special access holes can be supplied as made to order products.

Contact us for more information on our four metre diameter cover slabs.

Slabs in situ

Seating Slabs

Cover frame seating rings are reinforced 75mm thick units manufactured to suit cover slabs with a 600 x 600, 675 x 675 and 750 x 600 opening.

These are used in place of engineering bricks to adjust the metal covers and frames to the required level.


  • They can be quickly and easily installed by semi-skilled labour.
  • There are fewer joints – reducing the likelihood of infiltration.
  • All concrete manhole units can be ordered from one source.
  • There is a reduced risk of on-site damage and pilferage.

Units are made in accordance with BS 5911-3: 2010 and in compliance with safety guidelines given in the HSE publication ‘Safe Work in Confined Spaces’.

Supporting Image

Reducing Slabs

Type 2 at various chamber sections.
Typical reducing slabs are supplied as Type 2 to suit the various chamber sections, from DN 1200 to DN 3000 and have a 1200mm circular access.

Supporting Image

Landing Slabs

For sections of DN 2100 and greater.

Landing slabs can be made to suit chamber sections of DN 2100 and greater, with an access opening to accommodate customer requirements.


Contact us for specification assistance and to check availability.


Cover Slabs

Ring diameter
Depth of cover slab (mm)Overall diameter of cover slab
Standard access sizes (mm)Weight for unit 675×675 access
900150 1160EE0.16 t
10501501240EE0.28 t
12001501400EEMTOMTO0.40 t
13501501570EEMTOMTOE0.54 t
15001801770EEMTOMTOE0.90 t
18001802100EEMTOMTOE1.43 t
21001902500EEMTOMTOE2.18 t
24001902760EEMTOMTOE2.60 t
27002402980EEMTOMTOE4.00 t
30002403300EEMTOMTOE4.70 t

E Denotes eccentric position
MTO Made to order

Seating Slabs

Opening sizeOverall sizeDepth

Reducing + Landing Slabs

For shaft / chamber sectionApprox. depth including DN1200 shaft ringApprox. overall diameter

Resting Slabs

1800 x 500mm
2100 x 500mm
2400 x 500mm
2700 x 500mm
3000 x 500mm


AG operates a Quality Assurance Scheme to these standards to cover all aspects of production.All units are supplied with suitable lifting points.A precast concrete manhole is a strong, durable structure with its own inherent strength and does not require a concrete surround at standard depths.

More Information

All units are manufactured and tested in accordance with hEN 1917: 2002 – with the exception of Cover Slabs which is BS EN 1917: 2002 – and BS 5911-3: 2002 which, in addition to specifying dimensional tolerances, etc., clearly defines all the performance tests necessary to ensure that the product will perform satisfactorily in service.

Minimum order quantities are required for certain sizes, depths, colours, etc. Before placing an order, please speak to one of our sales teams – they’ll be happy to advise on this and any other product questions you may have.

You can reach them on:
UK: 0121 747 0202   |   Ireland: +44 (0)28 8778 8112

Case Studies

Featuring Slabs

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