The front end of the locomotive was of a typical Garratt arrangement with a water tank mounted on the front engine unit's frame, while the rear end was constructed in the Modified Fairlie fashion with the coal bunker mounted on a rigid extension of the locomotive's main frame and with the pivoting rear engine unit positioned beneath the coal bunker.

The main frame therefore carried the smokebox, boiler, firebox, cab, coal bunker, as well as the underbelly water tank.

[1][2][5] The Class GH were massive and powerful locomotives and, having been designed for passenger service, were built for speed with their large 60 inches (1,524 millimetres) diameter coupled wheels.

One reason which was put forward for the construction of the rear end of the Union Garratts on the Modified Fairlie principle was to enable their coal bunkers to be rigidly in line with their boiler frames to ensure a satisfactory arrangement for the installation of mechanical stokers.

The overhang, laden with the coal bunker which extended completely beyond the rear engine unit's pivot centre was subjected to severe vertical oscillation while the locomotive was in motion and this led to structural weakening of the frame over time.

The service career of the Class GH had a rough start, however, since on the first trip it was discovered that it exceeded the loading gauge in width.

[1] The Class GH made several trips working the Union Express out of Cape Town and was capable of taking the train up Hex River Railpass without a banker, but they were not as successful as had been hoped and they were soon taken off that duty.