A client in Lake Cathie (NSW 2445) decided to renovate and extend a 1960’s beachside shack. The renovation was in two stages. Stage one was the total gutting of the home and rebuilding with all new materials and adding a small extension for a second bathroom, which when Stage 2 was complete, would form an ensuite to a new master bedroom.
The two methods of building a foundation base for the two spaces were a traditional concrete slab 5m x 4m approx (see gallery below) and the second part of the extension utilising screw piers 7m x 4m approx (see photo gallery 2 below). In summary the concrete slab (20sq metrres) took around 5 days, many tradesmen (over 10) and around $10,000 in costs. The screw piers for a larger foundation, 28sq metres, used one small backhoe with one installer, 1 hour 10 minutes to install and cost $2,000.
CONCRETE SLAB METHOD:
A tale of an expensive unsustainable building method. A trench was dug by large backhoe to cater for the concrete footings with rubbish deposited on a once perfect lawn (destroyed in the process); concrete mixer arrived followed by concrete pumper and footings poured, pump cleaned over front lawn and ruined; bricklayers arrive and build retaining wall; some rubbish put back into the bricked lined hole, levelled out and tamped down with machine; termite spray, orange plastic sheeting laid, metal strengthening grid cut to size ; formed up; concrete mixer arrived for the second time followed by concrete pumper and the concrete is poured and levelled off, pump once again cleaned on-site and further destruction of lawn which the large pumper had already done some damage to the front garden. Total time: completed over 5 days. 9 tradesman on site over the 5 days: builder and offsider for form work; backhoe driver; 3 brick layers; concrete mixer driver; concrete pump and offsider. Work actually completed finished in a 9 day period as two days ‘lost’ for bad weather and two for a weekend. Cost: just over $10,000. Just to get a foundation of 20 sq metres
SCREW PIER FOUNDATIONS:
Truck and trailer with small backhoe and screw piers, arrived at 10.30am . The screw piers walked around the side of the home by the driver/operator, followed by the backhoe (an even smaller backhoe is available for tight access; the ground already marked for the position of the screw piers and with an assistant (the owner) the 12 screw piers were piled into position within 50 minutes. (Fewer piers could have ben used 9 – but the owner wanted more room under the floor for storage so the floor beams could be of a lower depth.) No rubbish to remove; low impact on the environment. Start to finish, including loading and unloading of backhoe 1 hour 10 minutes. Cost: under $3,000. Builder then laser marks the screw piers to get a level, cutes piers and welds a top L bracket (pre-made and holes drilled to piers), primes and paints the exposed piers and bolts on the floor-beam s and fixes floor joist on top. Time for builder to put in floor base – less than a day, so could be completed on the day of installation. Compared to a concrete slab (20sqm) the screw piers take 1 day as opposed to 5 working days and were a third of the cost for larger space (28sqm) and screw piers are not weather affected as they can be installed in the rain. And screw piers are so much kinder to the environment as well as the wallet.