The plan call for the construction of new additions under the existing buildings and the sinking of 125 new piles driven 29 feet onto the soil under the existing foundation, with all the walls being set on new re-enforced rail foundations. This was because the unstable nature of the earth had allowed the building to sink.
The whole layout was changed to isolated the main block from the goods shed and other building.
The booking, parcels and station master's offices all under went extensive alterations, and the men's waiting room was shifted to the middle of the building, plus new general waiting room and new women's waiting room; while the refreshment room was refitted to an improved standard.
The existing main entrance was closed and moved to the new booking office entrance built so it was no longer required to enter via the platform. The cantilever veranda was estended to go around the sides of the building. This brought the station in line with the railway's standard construction. It was estimated that about 16 Horsham workers were kept occupied for six months on the job. Approximately £1800 was spent in labour costs alone.
The plans, followed on from the new truck yards. The work was completed in 1940 including painting of the building.