The concrete raft is poured and is tidied up ready for the bricklaying to commence.
Reinforced concrete raft
The timber formwork is made, the steel reinforcing is in place and connected to the piles themselves.
There are two sheets of mesh held apart with spacers. The layout of the steel reinforcing is designed by our structural engineer.
Beneath the steel mesh is a void former, this is a collapsable material, such as Claymaster, which is strong enough to support the weight of the concrete, but will disintegrate over time to leave a space beneath the raft. This space will allow the ground to swell without affecting the new structure.
The piles tubes come in two metre sections and have to be welded together as they disappear into the ground. The piles typically stop at about seven metres, although on some jobs they have gone down over twelve metres! The hollow tubes are then filled with concrete.
In this job we have had to reconfigure a lot of drainage so there is more mess than usual, normally the piling is quite a neat and tidy process.
In his youth, Dave used to weld undersea oil pipelines in the Gulf, wearing full diving gear, so this is a piece of cake for him! Apparently they could only be underwater for a limited amount of time each shift due to decompression issues, so they had to spend the rest of the day lounging around the boat in the sun, drinking G&T. It doesn’t look quite as glamorous in the photo, but it’s still an important job.
Orangery Foundations – Piling
The ground conditions dictated that deep piled foundations were required on this job. The access at the side of the property was limited, and the clients has a relatively new patio, so using a mechanical excavator wasn’t really an option.
Our preferred method in this situation is to use bottom-driven piles. We have used them on enough jobs over the years to warrant investing in the equipment and training ourselves. The piles are specified by a geotechnical engineer in conjunction with our own structural engineer.
The piles are typically placed about two metres apart and connected with steel reinforcing. We use either a reinforced-concrete groundbeam or a reinforced-concrete raft depending on the situation. On this job we will use a raft.
The equipment is heavy but portable, the power is provided by a compressor which can be left at the front of the property and connected to the piling hammer by air hoses.