Speeding up social housing delivery in the Western Cape
The Portland Group, the holding company of Portland Hollowcore, which is a family-owned business, has been in existence since 1988 and in 2000 purchased the Portland Quarry. The company is well known for the quality of aggregate their quarry produces. Portland Hollowcore manufactures precast concrete panels at their Durbanville premises in a purpose made factory. The panels are reinforced with pre-stressed cables and are formed in an extrusion process with machinery and technology supplied by Elematic, Finland.
Social housing, which is defined as rental units aimed at low income households, which are administered by Independent Social Housing Institutions, who are granted state-subsidies to build the units. The backlog in the development and delivery of social housing in the Western Cape is estimated to be over 350,000, with a national figure for South Africa of over two million units. Social housing is one form of housing delivery that is aimed at enabling those who are not able to obtain traditional financing options, to rent a property.
“The demand for social housing in the Western Cape, like elsewhere in the country, is enormous. With the time and cost efficiencies that can be achieved by utilising precast concrete panels, I believe that once developers, who are used to traditional and historical methods of building houses and apartments, embrace this technology further, we can make a substantial and positive impact on budgets and delivery. The key to improving delivery of units, thereby reducing the backlog, is most certainly the precast concrete way, due to its faster and more financially competitive production time” said Nico Heyns, Managing Director of Portland Hollowcore.
“A critical factor to our improved production processes has been the Elematic technology. The new machinery enables us to cast at a faster speed and in more lanes per day - we are able to produce more meters of concrete per minute - and the quality is better. The Elematic machines have resulted in substantially less factory downtime, due to the preventative maintenance scheduling which we adhere to. The machines offer us a lifecycle of between 15-20 years. At any given point in time we are supplying a number of clients whose projects are either on-going or where numerous houses are being constructed. Our precast installations are completed within one day” he said.
Nico Heyns continued “When we visited the BAUMA Expo in Munich in 2008 we were introduced to Elematic. We were impressed by their machines and technical support and how it could enhance our production processes and reduce costs; savings which we could pass on to the developers of social housing in the Western Cape”.
Projects and Awards
Portland offers a full turnkey solution of design, the manufacture of specified precast concrete panels at their factory and delivery to and installation at site. Portland Hollowcore is currently supplying over 150,000 square meters of panels to projects developed by Calgro M3 around the greater Cape Town area. They have also supplied decking and stairs to the Belhar social housing project.
The application for Portland’s precast concrete panels is not restricted to social housing. One of the projects the company is very proud of is the V & A Waterfront parking system – the first ever demountable parking deck in South Africa. The concept was developed by V & A Waterfront and LH Consulting. Due to its popularity in high season, the V & A Waterfront needed additional parking capability, without tying up valuable land space permanently. The demountable parking system gives the V & A the opportunity to either sell the parking to another party for re-erection or they can move the parking to another area.
Nico Heyns explained “We used 200mm thick slabs at an 8m span. There is no structural topping or screed done on top of the slabs as it is demountable. There was a special mix of 35Mpa developed by Portland’s technical team together with LH Consulting to do the grouting of the V joints. This mix design is being manipulated to bond the slabs together but also to ensure minimum broken panels when the parking is being dismantled. The super structure of this building was done in approximately 60 working days. It is a great way to build a parking deck and we are confident that no other system can compete with our erection speed”.
Portland Hollowcore joined the Concrete Manufacturer’s Association (CMA) in 2014 and submitted The Gene Louw Primary School Activity Centre in Durbanville, another of their projects, into the 2016 CMA Awards. The DF Malan High-School Multi-Purpose Centre project was a 2013 Fulton Awards Nominee.
More recently the company installed 200 mm precast concrete panels to the brand new Reddam House School in Durbanville; Nico said “It was an honour to be part of the construction of such an amazing building which is situated right on our doorstep. This school is a state of the art development with the latest finishes and facilities throughout”.
“Using precast concrete slabs definitely offers substantial savings in time. It is less labour intensive for the contractor and offers up to 30 days less standing time on one simple deck. When we install the panels, the client only has to fill the joints and put a screed on top – that takes one day. So while the cost of prefabrication is not necessarily cheaper, the trickle down on-site activities such as transportation, labour and time are all either eliminated or substantially reduced” said Nico Heyns.
Portland Hollowcore has two Elematic Extruders and an efficient Elematic saw assisting them to increase their production of precast concrete panels. “Due to a rising order book for our precast product, we chose to airfreight the new Elematic Extruder to South Africa. We needed more capacity and quickly. While the costs to do this were higher than sea freight, our return on investment was within one month of operation”.
Nico highlighted the fact that the new extruder enables them to manufacture 250 mm thick slabs, whereas before they could only manufacture 160mm and 200 mm thick slabs. The 160mm slabs are mostly utilised in residential housing. “Our experience on the V & A Waterfront parking project using our thickest sized slab highlighted the potential for greater applications for our precast concrete products. The thicker the slab the longer you can span, therefore making it suitable for use in high-rise building developments in Cape Town, as well as parkades and office blocks. The Elematic Extruder offers us extra capability and flexibility, which in turn enables us to look at these opportunities in addition to servicing the social housing sector” she said.
Portland Hollowcore’s investment into more advanced machinery enables them to manufacture concrete panels throughout the day, leaving the panels to cure overnight, and be ready for cutting and delivery all within a 24 hour window. Nico said “There is a better quality product being manufactured now that new processes have settled down. We hold weekly quality meetings and conduct quality tests in a controlled environment. In our line of work there is no room for error with our product, the consequences could be catastrophic. We are an extremely quality confident outfit”.
“We have a strong relationship with Portland Hollowcore. Their factories have a well-planned layout that will allow them to expand their production when needed. Our warehouse in Dubai ensures that we are able to assist our South African customer base quickly and efficiently”.” said Curt Lindroth, Area Sales Director for Elematic, Finland.
Nico concluded “We hope to expand our production facility shortly. We do intend to stay with Elematic, their machinery is high quality and their support and service is their key differentiator’.
ONE OF THE MOST SUITABLE PRODUCTS IN CONSTRUCTION: the hollow-core slab
Hollow-core slabs are precast slabs of pre-stressed concrete typically used in the construction of floors in multi-storey residential, commercial, office, and industrial buildings. It is also possible to use hollow-core slabs in vertical or horizontal installations as walls or noise barriers. The slab has been especially popular in Northern Europe, where the emphasis of home construction has been on precast concrete. There are different types of hollow-core slabs. Usually, the standard width is 1,200 mm.
Savings in concrete
The highly optimized and economical use of material makes hollow-core slabs one of the most sustainable products in construction.
The precast concrete slab has tubular voids running the full length of the slab, making it much lighter than a massive solid concrete floor slab of equal thickness or strength.
In the cross section of hollow-core slabs, concrete is used only where it is actually needed. Areas in which concrete acts only as ballast are replaced with hollows. For instance, in 200-mm hollow-core slabs, 49.9 percent of the cross section consists of voids. In 400-mm hollow-core slabs, this percentage may be as high as 55.6. This brings savings in concrete material costs, as well savings in vertical structures, foundations and reinforcement.
Freedom for individual design
When a building with hollow-core slabs is designed, the lightweight, long-span solution offers more possibilities compared to traditional massive short-span slabs. When hollow-core slabs are used in residential buildings, the partition walls inside flats can usually be non-load bearing. This gives freedom for the individual design of flats, as well as for modifications during the building’s lifetime.
In commercial and public buildings, long-span hollow-core slabs have enabled comfortable car parks to be built without pillars, with quick and easy access and exit.