To report the 5-year outcomes of autogenous bone block grafts fixed at a distance (BBG-D) versus a resorbable poly-D-L-lactide foil fixed at a distance (SonicWeld Rx shell technique SWST) randomised controlled trial, for lateral alveolar ridge augmentation. Thirty patients with a buccopalatal bone width of ≤ 3 mm were randomised into the following treatment groups: BBG-D and SWST. The implant survival, changes in bone morphology visualised in a cone beam computed tomography scan and periodontal parameters were assessed. Thirteen patients in the BBG-D group and seven in the SWST group could be included in the analysis. All implants that osseointegrated initially (BBG-D = 13 and SWST = 7) were functional at the 5-year re-evaluation. The buccopalatal bone width significantly (P < 0.001) decreased over time regardless of the study group. A bone loss of 0.00 mm was observed at the distal implant shoulder in the BBG-D group and 0.29 mm (SD 0.49 mm) in the SWST group (P = 0.04). The mean buccal bone loss was 2.56 mm (SD 3.65 mm) in the BBG-D group and 1.71 mm (SD 4.11 mm) in the SWST group (P = 0.64). The mean probing pocket depth was within sound limits in both groups without significant differences (P > 0.05). Bleeding on probing was low. Within the limitations of this study, a similar implant survival rate was observed between the BBG-D and SWST techniques during the 5-year follow-up. The buccopalatal bone width decreased over time regardless of the augmentation method used.