The original sedion of the four-storey building was designed by Dublin archived Mr. Charles Geoghegan to accommodate one hundred pupils (see relevant perspective drawing/painting). It was built by the building firm Beardwood at a cost of £11,000. It comprised a centre block (three windows wide) with adjoining four window wide wings on each side.The Builder a professional journal published in 1857 describes the plan of the building as:

“An elongated parallelogram having a centre projection beyond the limits of the wings at front and rear appropriated to the use of the ‘Christian Brothers’. In the wings which are connected to the centre by corridors, having glass doors are contained the schools chapel refectory dormitories, playroom kitchen, staircase and interior offices…”

The five acre lands of St. Joseph’s School were formerly part of over 94 acres of Cabragh property owned by the Segrave Family, dating back to the mid-seventeenth century. Thanks to the great efforts of Fr. Mc Namara C.M. (Member of Catholic Institute for the Deaf), a lease forever was secured from the landlord Captain ONeill Segrave for the school. Br. J.S. Galvin of St. losephs school wrote an interesting history of the Cabragh district which can be read in the
Centenary Record 1857-1957 of St. Joseph’s School.

Several reports were published in ‘The Builder’ highlighting the building-works being carried out on the site of St. Joseph’s School e.g.

‘The building is ofgothic Tudor style erected of rubble, masonry limestone pebbledashed having the quoins cornices windowdressings etc of red bricks from Wexford and windowsills corbels, gable crosses copings, etc of County Dublin granite..’

In 1869 the east wing of the main building was built comprising the refectory and chapel at a total cost of £5,000. Later additions took place in the 1870s including the imposing west wing which housed an assembly hall/school-room. The school room being 154 feet long by 40 feet wide was described as: “One of the finest halls in the British isles at that time, appropriated to educational purposes.”

Also the grounds around the building were improved and extensively landscaped. Other extensions and renovations took place over the years. These included the Front Lodge and Model farmyard buildings.

Major alterations/renovations were carried out to the building around 1934/5. They included a new intermediate floor-level in the west wing consisting of new classrooms (see relevant drawing-plans). ln the midseventies a new school building was built opposite the old Infirmary.

ln the mideighties the famed old Navan Road entrance to the school had with much sadness to be relocated to the Ratoath Road to facilitate the ever busy volume/movement of traffic at Cabra Cross.