Reducing Height Of Manhole Cover

[maharg]

Our patio was made of concrete 8 metres wide by 5 metres long and 0.2 metres deep.The concrete was laid 50 mm below the DPC.
I have removed the concrete and a further 0.2 metres of bricks,paving stones used as hardcore.
I intend to replace patio with decking.
My problem is there are 2 manhole covers in the area.These were raised by 450 mm above the original ground level by oversailing 5/6 courses of house brick and concrete to reduce the opening from 1200mm x1000 mm to 650mmx450mm.
I need to reduce the height of the inspection covers by 400mm.
Just taking of 5 courses will get me to level ground but I then have a 1200x1000 opening that needs an inspection cover.
The chamber is 1.5 metres deep.
I presume I could take a further 5 courses and oversail with engineering bricks up till I reach ground level or take of 2/3 courses and use a biscuit to reduce the opening but I am really looking for advice on whether these options are correct or there are better alternatives.
Any advice would be gratefully received

[welsh brickie]

to reduce the size of the opening use concrete lintols to span the manhole you dont need to oversail the brickwork.

[Sooze]

to reduce the size of the opening use concrete lintols to span the manhole you dont need to oversail the brickwork.

Your description of a manhole reduction problem does not provide enough clues to enable anyone to make completely useful comments but it has caught my attention. If the nearest manhole cover to your damp course is much higher then it sounds as though you are on sloping ground and other properties are likely to line up at the same level. Obviously you have considered who would be the unlucky recipient of a blocked drain if yours was 400mm below everyone elses? You did not explain if the manhole was of a professionally established brick, moulded concrete or rounded plastic construction so without enough information I would simply like to contribute a brief polite comment:
Consider ground level with adjacent properties and their drain covers
consider the age and professional standard of existing construction
Consider the reason why someone else built something that you now want to change
Consider that all properties need 2 bricks clear below damp couse to avoid damp problems
Consider that there are 1000's of experienced plumbers and ground worker who may offer
free advice if you simply want to call them out of the telephone directory? ? ?

[welsh brickie]

sooze. the information was posted a year ago,If the person wanted more information they could have asked for more clarification.If you have read half my posts then you would realise I am a proffesional qualifed builder with over 25 years experience.