Waterfront Development Requires Specialist Skills

Now in its fourth year the awards cover the entire property industry with Regatta Quay, redeveloped by City Living Developments, one of four winners within the Best UK Development category. Other categories included interior design and architecture, with Regatta Quay named as one of 20 winners in total.
For 160 years the site, originally known as Albion Wharf, echoed to the sounds of the malting industry, and Paul's Maltings, alongside the Old Customs House, was at the heart of this industry, which dominated the town of Ipswich during the 19th and 20th centuries.
In its heyday it produced 30,000 tons of malt a year, which was exported around the world, but with the development of newer and larger maltings the industry moved away from the Ipswich waterfront, which lapsed into disrepair. The area is now in the process of regeneration as new restaurants, bars, marinas and homes spring up.
Albion Wharf itself, which was the last malting to close in November 2004, is being sympathetically redeveloped as Regatta Quay by City Living Developments to reflect both the history of the wharf and the aspirations of a modern waterside residential development at the centre of the current regeneration.

When the developer took over the site, Block A was an old yard area and Block B was a modern brick building sitting on strip foundations. Block C was occupied by relatively modern concrete silos which were in good condition and had massive piled foundations whilst Block D, which was the malt house, was in a poor state of repair with cracked and defective brickwork, rotten timbers, crumbling roof etc.
Blocks B and C were demolished for the new development, but the old 19th century malt house is being carefully restored to preserve the character of the area and provide modern residential accommodation.
The redevelopment of the site has provided Glanville Consultants, the engineers, with a number of challenges. There were no records of the old foundations, which have had to be removed to allow the construction of foundations for the new buildings. It was not viable however to remove the existing piling and consequently the new foundations have had to be designed and constructed around them with eccentric loads, and the moments taken out in the pile caps and ground beams.
The site, standing adjacent to the old dock wall, has a high water table, which is tidal and varies between 1m and 2.5m below ground level. Soil conditions at the site consist of made ground overlying soft alluvial deposits which in turn overlay the chalk bedrock. For these ground conditions it was decided to use piled foundations and a continuous flight auger rig was the preferred method of installation. An 800mm piling mat was installed using the hardcore from the demolition of the old buildings and their foundations with layers of geo-textile fabric to give it stability.

To avoid additional costs due to pumping of groundwater one of the design criteria was to maintain the new foundations above the highest water level on the site and in general this was achieved with the exception of certain lift pits and their associated pile caps and ground beams where some tidal working was necessary. The mat was also laid to appropriate levels to allow the construction of ground floor slabs and external courtyards.
The soil and groundwater conditions on the site are not particularly aggressive and no additional measures were considered necessary to protect the new foundations. Any contaminated material was removed as part of the remediation programme.
The old Victorian sewer which runs across the site was protected with steel sheets during the piling operation but otherwise no protective measures were considered necessary because dock traffic had run across it for 150 years.
Blocks A, B and C are all new build construction and each consists of a series of interlinked buildings of varying height, the tallest buildings, in each block being 17, 6 and 15 floors respectively. External cladding to the buildings is a mixture of brick, terra cotta and stonework.
For the new buildings a steel frame and metal decking would have provided an economical solution but the downstand beams in shallow ceiling voids present problems for the service runs. Also modern noise and vibration regulations make detailing of steel frames in flats difficult and with the irregular shapes of these buildings it would have led to a complex arrangement of steelwork.
The preferred solution was therefore a concrete frame with a flat slab, giving better sound and fire installation and also less hindrance to the installation of building services. A number of factors predicated a series of compromises that resulted in slab depths at 275mm with spans at up to 8m. Deeper slabs save on reinforcement costs but increase foundation loads and building heights, which offsets the savings.
Modern finite element computer analysis facilitates the decision making process. But in practice the limiting factor often tends to be the punching shear around the columns.

Concrete strengths for the columns in the new blocks were raised from C40 to C60 to accommodate the higher loading. This was not necessary in all cases but was used across the site to avoid any confusion and at little extra cost.
Transfer slabs 915 mm deep were introduced at first floor to span over the 14m wide access road, and ground beams were added to carry the road over the old 1200 mm diameter Victorian sewer.
Stability for the tall blocks is provided by 215 mm shear walls around the cores. The design of the shear walls was complicated by the need to provide service penetrations through the walls. The lower floors will be used for commercial purposes, whilst the upper floors will be purely residential. The internal finishes are currently being finalised.
Within the residential areas there is a suspended plasterboard ceiling allowing a 100 mm void for services distribution. Floor finishes consist of a 40mm self-levelling screed cast directly onto the structural slab with electric under-floor heating cast in. Other services provided include telephone and cable TV, and these also provide internet access.
Block D is the old malt house, which is being maintained and refurbished to provide accommodation on five floors including the mezzanine level. The existing structure consists of cast iron columns and mild steel beams with generally timber floor construction. Block D1, at the front is being fully refurbished and most of the timber floors are being renewed. Block D2, at the rear is being stripped out, the external walls are being retained and a new steel frame with concrete slabs on metal decking, to give better fire and sound insulation, is being built inside.
A new lift and staircases core has been introduced to service the apartments and improve lateral stability. The new core is carried on mini piles going down 16 to 17m.
These changes to the structure result in a small reduction in overall foundation loading. Block D also incorporates a new single story storage block with concrete ground and mezzanine floors and a timber flat roof. The floors are carried on masonry walls down to ground beams and onto piles. Block A includes a small theatre which will provide facilities for local professional and amateur companies.

An unusual feature of the development is the inclusion of car stackers within Blocks A and C to provide one car parking space for every apartment. Other alternatives considered were a single-story basement across the site and a multi-storey, aboveground, car park.
A single story basement car park would be the normal choice for a development of this nature, however this was considered to be both impractical and uneconomic with the tidal groundwater, the soft nature of the upper stratum, the presence of the piling from the existing buildings and the old Victorian sewer. The existing malt house, sitting across the middle of the site, further complicated the basement option.
A multi-storey above ground car park was also investigated but the circulation space required to give access would reduce the number of apartments that could be built and thereby reduce the viability of the development. A further advantage of the car stacker is that it will provide added security for parked cars.
Looking back over the planning and design stages of this project, Glanville’s Nigel Porter says “The developer’s objective was to create an attractive marina and dock-side environment through the combination of tastefully converted original buildings and new-build using a variety of complementary materials. As is common in waterside developments, a number of interesting challenges had to be surmounted and we are delighted with the final scheme. Building is progressing well and some flats are now on the market and ready for occupation.”
Over recent years, Glanville Consultants have become accustomed to the challenges of dealing with the problems presented by waterside developments. The company currently has major residential projects on site in Oxford adjacent to the canal and the River Thames, in Norwich on the bank of the River Wensum and in Worcester where the redevelopment of the old Porcelain works is situated at the junction of the Birmingham and Worcester canal with the River Severn.