The Guest Street scheme is part of the New Islington project and as such was included as part of the sitewide masterplan, which included a large-scale ground treatment and remediation strategy. The site itself has had canal-related development stretching back over 150 years and most recently was a parking and maintenance depot for trucks and wagons. These operations caused some ground contamination, largely in the form of infilled canal arms with limited amounts of residual hydrocarbons. The New Islington framework contractor undertook site remediation to pre-agreed standards and the contractor supplemented these measures to higher standards as the design for the project became clearer.
For example, when the extent of gardens became fixed, these areas were treated to a higher standard. Once the site had been prepared, foundations consisting of piled ground beams were installed, stepping up from the lowest level at the Stubbs Mill end of the terrace up to Carruthers Street. There was also a need to retain and protect the local clinic building and Carruthers Street itself at the east end of the site. These elements are appreciably higher, at approximately 1.3-1.5m high, than the ground-floor level of the affected terraces. This involved some additional mass concrete retaining walls along the interface with the clinic. A reinforced and tanked concrete upstand was installed where the structure abutted Carruthers Street, upholding the carriageway and integrated into the fabric of the end terrace itself. The ground floors were constructed from precast beam-and-block units, with the building envelope consisting of an internal load-bearing masonry leaf with cavity and brick outer leaf. There was a desire to keep the ground-floor plate open-plan, and this meant designing a centrally positioned brick pier with steel joists spanning to perimeter walls to carry first-floor partitions and floors. The flat roofs are simple timber joists with a plywood skin, which carry a sedum covering to create green roofs.