Cover, seating, reducing and landing slabs

Cover Slabs

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

These slabs come in a range of dimensions, however non-standard slabs 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.

Seating Slabs

Cover frame seating rings are reinforced 70mm 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’.

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.

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 675x675 access
600x600 675x675 750x600 750x750 1200x675
675 140 960 C C X X X 0.13 t
900 150  1160 C C X X X 0.16 t
1050 150 1240  E C X MTO X 0.28 t
1200 150 1400  E C E MTO X 0.40 t
1350 150 1570  E E E MTO MTO 0.54 t
1500 180 1770  E E E MTO MTO 0.90 t
1800 180 2100  E E E MTO MTO 1.43 t
2100 190 2500  E E E MTO  MTO 2.18 t
2400 190 2760  E E E MTO MTO 2.60 t
2700 240 2980  E E E MTO MTO 4.00 t
3000 240 3300  E E E MTO MTO 4.70 t
3500 275 3850  MTO MTO MTO MTO MTO 7.40 t
4000 275 4500  MTO MTO MTO MTO MTO 10.50 t


C - Denotes central position
E - Denotes eccentric position
X - Unavailable
MTO - Made to order

Seating Slabs

Opening size Overall size Depth
mm mm mm
600x600 750x750 75
675x675 850x850 75
750x600 880x750 75

Reducing + Landing Slabs

For shaft / chamber section Approx. depth including DN1200 shaft ring Approx. overall diameter
DN mm mm
1500 250 1770
1800 250 2100
2100 250 2480
2400 250 2780
2700 250 3000
3000 250 3300

More Information

AG operates a Quality Assurance Scheme to these standards to cover all aspects of production.

All units are manufactured and tested in accordance with 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 products and sizes. 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 0121 747 0202 in UK and on +44 (0)28 8778 8112 in Ireland.




Have you considered...

Sign up for our newsletter to get the latest updates on AG's products and services.