A flowline branch structure (10) has at least one inner branch assembly with an inner flowline branch and at least one inner flowline pipe attached to and communicating with the inner flowline branch. At least one outer branch assembly (12) of the flowline branch structure has an outer branch housing disposed around the inner flowline branch and at least one outer pipe (14) disposed around the inner flowline pipe and attached to the outer branch housing. A generally annular space is defined between the inner and outer branch assemblies. At least one wiring element including an electrical heating element is disposed in the sealed space on an outer side of the inner branch assembly. The, or each, wiring element extends in one continuous length across an interface between the inner flowline pipe and the inner flowline branch. This reduces the number of connections necessary to create the flowline branch structure.