Convent Lands, Portlaoise, Co. Laois

Summary

Sophia Housing engaged ROD to provide civil and structural engineering services for the redevelopment of the Presentation Convent and Sacred Heart National School lands in Portlaoise. Our design partners were: OBFA Architects, Reddy Architecture and Urbanism, Lotts Architecture and Varming Consulting Engineers.

In addition to providing much-needed housing in Portlaoise, the development incorporates a substantial public realm upgrade, making the town a more attractive place to live, work and visit.

Background

The Presentation Convent

The Presentation Convent is situated in Portlaoise town centre and forms part of a larger complex of community buildings on Church Avenue. The convent was established in 1824 and was later extended into adjoining buildings, including a historic stone tower that dates from 1548. Further extensions were added in the late nineteenth century and the twentieth century.

The Sacred Heart National School

The Sacred Heart National School is one of a group of buildings to the south of the convent building. The original national school dates from c.1880, and a new block and wing were added c.1930.

Solution

The project comprised the construction of a 50-unit residential development at the site of the Presentation Convent, Sacred Heart Primary School and adjacent grounds and buildings. It involved the alteration and refurbishment of the school and convent buildings and the demolition of ancillary buildings and prefabs.

A new three-storey apartment block replaced ancillary buildings to the south-west of the site. A five-unit terrace and a three-storey apartment block replaced existing prefabs to the north of the convent.

Complicated phasing was required to enable the existing convent building to be made safe for conservation and geometric surveys to be undertaken.

Approach

Our buildings group led this multidisciplinary project, with inputs from our ecology, traffic and water teams. Our ecology team took responsibility for the bats and invasive species on site, while our traffic and transport team provided a detailed traffic impact assessment. At the same time, our water team carried out complicated flood modelling on the site.

During the construction of the works, the main contractor, Bretland Construction, proposed a significant change to a fully precast solution. Our buildings team worked closely with them to bring this approach to fruition, allowing the blocks to be completed ahead of programme.

The project added contemporary, low-rise housing, in two blocks, overlooking the mature gardens.

Challenges

The Stage 1 and 2 Flood Risk Assessments (FRAs) identified that portions of the site were within Flood Zones A and B (1 in 100 and 1-in-1000-year flood extents). Our water team subsequently undertook a Stage 3 detailed FRA, including a 1D/2D hydraulic model of the River Triogue catchment within Portlaoise, to confirm the effects of extreme fluvial flood events in the existing and post-development scenarios.

As a result of our analysis work, the preliminary layout of the building was amended to ensure minimal impact on flow paths and flood water displacement within the floodplain caused by the proposed development. A structural solution for the building was developed that features a finished floor level, supported 1.5m above ground level by a series of concrete fins. The fins allow water to pass under the building during a 1–1000-year event.