You can buy deeper pre-stressed concrete lintels to suit your needs.
Just found out I coulld just buy a 900 x 600 cover; that would mean no need for lintels. As said, would cover with gravel. Any reason why not to use the bigger sized cover?
Cheers
You can buy deeper pre-stressed concrete lintels to suit your needs.
No reason, saves you a ton of work, just make sure it is well supported on all edges.
Thats plenty, I would crack on.