If I am looking to extend off a house, which is built off piles and rc ground beams, is there a standard practise to dowel a new section of ringbeam to the old one?

 

If I have had an SE calculate for beams and provide bending schedule, should there be accompanying advice on anchoring old rc beam to new one?

It depends. Can be done either way. If you are keying together blockwork, roof structure etc then you'd pin the foundation together. But you can also have the new structure independent from the old one, I e. Have a gap between the blockwork and fill later with mastic. You then don't pin the founds as you want them to move independently. We did the latter as the new foundations needed to be deeper an lower than the original so wouldn't have worked anyway. 2 Speak to you SE.