The Carriage Works is one of the main facilities of Boston Lodge works. In it vintage carriages are restored and new ones built for the Ffestiniog and Welsh Highland Railways. Contract work is also carried out for other railways and organisations. The carriage works is also home to the railways' painters.
The new Carriage Works building in Glan y mor yard was started in the late 1970s and by Sept 1977 had the main roof on but no north wall or doors, but could be used to shelter vehicles. In 1980 doors were fitted and some woodworking machinery installed and in 1981 all equipment from the previous Carriage Works in the old Carriage Shed Paint Shop was moved in and four carriages could now be worked on simultaneously under cover.
It has subsequently been extended with a new three road workshop building at the rear. This new building is known as the Heritage Lottery Fund (or HLF) shed after the source of its funding.
The HLF shed at the rear is generally used for major construction and restoration projects and is where the woodwork is completed for new carriages (the metal frames are usually built in the erecting shop). The older shed is generally used as a paint shop and for more minor works.