Cracking at junction of extension and main house

I have cracking on one side of a single floor extension at the junction with the main house from settlement, that has cracked internal plaster at the corresponding wall junction. Job will be to fill in external crack with flexible filler and re-point and also rake out and fill internal crack before plastering/skimming small room...what type of job should I post this up as, and is Builders the right category? Thanks