Questions on bridging foundation gap for drains

[pilsbury]

Foundations poured with a gap left for the main sewer run to pass through. Will be starting the bricking below DPC this weekend and I'm aware to use concrete lintels to bridge the gap in the foundations.

My initial thoughts were to use 2 100mm wide lintels, but then cosidered I'll have an open gap underneath the cavity. How do I get around this? Shutter off underneath with ply when I do my weak mix fill for the cavity below DPC? Look for a 300mm wide lintel? Lay 3 100mm lintels side by side?

Also, what is the recommended thickness of a lintel for a single storey block extension?

 

[noseall]

Lay 3 100mm lintels side by side?

Seems sensible. 150mm wide fellas are available but not much better.

Also, what is the recommended thickness of a lintel for a single storey block extension?

Same length as that piece of string?

Usually 100mm deep concrete lintels will suffice on anything up to standard door sized openings - i.e. up to 1m wide etc. However, as with this type of lintel, it depends where it is located in terms or point loading and the amount of masonry going above it.