Hi. You have the option to chop as to access the irons but this will not give you rigidity or monolithism in the structure. Where do you want to get hooked is an existing building well set? Do you already have your time? In this case and to avoid cracks and achieve monolithism in the structures you must use a special product that is a transition between already set or existing concrete and a new one. I leave the link of the sticker. With this you will be sure of a good job, there will be no cracks and you will have mechanical continuity in the concrete. regards https://arg.sika.com/dms/getdocument.get/843c455f-934c-3d51-b0ba-b3fbf6298f08/Sikadur-32%20Gel.pdf