Portishead Marina is a major redevelopment of the former dock area, which involves a variety of two and three- story houses and six storey apartment block on the harbour front. The town houses in some of the phases were constructed using Corus' Surebuild system.

The six storey block was originally designed in reinforced concrete but the developer, Crest Nicholson, wished to reduce the piled foundation costs. 

A value engineering exercise was used to evaluate various alternative schemes, of which included Slimdek®. The design also included a below ground car park and a by slight adjustment tocolumn positions, the Slimdek design was able to eliminate the expensive transfer structure at ground floor, as well as reducing foundation loads by 30 percent. The overall savings were significant and led to the final choice of Slimdek. 

A range of apartments of 46 to 62 m² floor area each have large panoramic windows and some have prefabricated balconies. Columns were designed to fit in the separating walls and façade walls. The chosen cladding was brick work to create a more traditional ‘feel' for this riverside perspective. Other builders used an insulated render system above first floor and brick work at ground floor.

Floor spans of slimdek ranged up to 5.5 metres, which allowed the use of two bay car parking below ground. The one hour fire resistance was achieved by the partially encased ASB beams and bar reinforced placed in ribs of the deep decking.

A further six storey building in this project is under way using slimdek, building on the success of this phase.

Construction Details

The steel structure consists of 280 ASB 100 sections spanning up to 5.5 metre between steel columns, which are located in separating walls. The 300 mm deep composite slab spans between cross-walls and did not require temporary propping. Plasterboard was fixed on resilient bars directly attached to the decking.

A heavy duty mineral wool layer and flooring board provided the impact sound insulation (the slab ceiling on its own was sufficient for airborne insulation). The completed floor depth is only 400 mm.

The discrete columns and flat soffit meant that the non-load bearing walls could be placed to suit the required floor plan of the apartments. Large window bays were located between the column. The column spacing was carefully selected in order to suit an efficient layout for car parking which eliminated the need for a transfer structure at ground floor. The car park area was sufficiently well ventilated in order that it could be designed for one hour fire resistance without additional protection. Stability was provided by bracing stairwells and lifts.

The self weight of the structure and imposing loading was only 70 percent of that of the original 250 mm reinforced concrete slab which, with the loss of the transfer structure, meant that the foundation loads piling costs were reduced by 30 percent. Speed of construction was also improved by some 30 percent, which led to associated savings in carnage costs and site preliminaries. Pre-fabricated balconies were directly attached to the perimeter of the slab to improve the speed of insulation further.

Key information

Number of storeys	6
Living area (m2)	46 - 62 m2
New-build home

    High Quality Apartments Using Slimdek at Portishead marina