Large shed at builders' yard ('John Graham Construction'), Lagan Mills, off Lower Mount Street, Dromore, Co Down, BT25 1AS

Large single storey builders' store at Lagan Mills, off Lower Mount Street, Dromore, dating from approximately 1935-40. The building features a Belfast Truss roof, a design developed in the mid-nineteenth century to provide efficient, lightweight, long-span structures for industrial use. The Belfast truss employs bowstring girders with internal bracing members meeting on the top curved member rather than at the bottom, as was conventional. The design was pioneered by Belfast felt-makers McTear & Co., first referenced in an 1866 advertisement in the Dublin Builder. After McTear & Co. ceased business in 1908, Anderson & Co., another Belfast felt supplier, produced trusses from 1886 onwards. Anderson's Mark II version, launched in 1896 and designed to maximise long spans while maintaining light weight, became widely adopted and established the model known as the Belfast truss.

The building is rectangular in plan, measuring approximately 31.3 metres by 11.9 metres, and is constructed in brick with later alterations in breeze block. The north elevation retains original brownish brick on the far left side, with the remainder in later breeze block, possibly replacing boarded cladding or large doors. Two large timber vehicle doorways with sliding double doors and high-level glazed panels are positioned on this elevation, along with a boarded window opening at the far left.

The east (gabled) elevation is in original brick with a tall stepped parapet rising into a shallow gable. Two large doorways occupy this elevation, both appearing to be redundant loading bay doorways set slightly above ground level. The left doorway retains a timber and glazed door similar to those on the north elevation, while the right doorway is boarded up.

To the west, the store abuts a separate building. The south elevation is in brick and features a long row of large windows with mullioned and transomed frames, each separated by a pier. The curved roof is felt-covered with a central row of relatively large gabled skylights.

The building is of industrial archaeological interest and lies within a conservation area. Its front elevation has undergone significant later alteration, though it remains a relatively rare example of a large Belfast Truss-roofed builders' store of this period.