Dartmouth 2011 - Excavation of terraces & construction of stone wall retaining and natural stone paving
This proved to be a challenging but rewarding project. To the left is a photo of the site on the first day and below are two images of the 3D design provided by the client we were working to. The plan was to terrace the higher lawn area removing hundreds of tons of soil and create much more space on the lower level which was to become a large stone paved seating area. The terrace walls were to be built from local stone with planting beds on each terrace. On the left side were to be steps on to a small sun terrace and on the right hand side steps leading up to the lawn area above.
Within minutes of starting the excavation the first problem emerged; numerous services just below ground level including 2 water pipes, 2 mains supply power cables and an 2 underground phone lines. Progress was slow working carefully around all of these obstructions, the water pipes being quite simple to extend and re route, but the electricity lines requiring the power board to extend the cables. We then installed new ducting to take the phone lines and all the services were grouped together and redirected around the top of the excavation behind the top wall.
With the digging complete the next challenge was to deal with extraordinary amounts of water flowing from every level of the excavation which was soaking away into the back wall of the house and causing damp. The cause of this was an old stream bed running right through the middle of the site that had been diverted just above the site many years earlier. We laid extensive drainage on each level to catch this water which was then picked up by a central pipe following the old stream bed to the bottom level where the water was channeled away by a final trench dug into solid bedrock and taken round the side of the house. We then dug a final trench along the damp wall of the house, underpinned areas that had deteriorated with new stonework and finished by water proof rendering to just above where the new paving height was to be.
We were now ready to start building the stone walls. Firstly concrete footings were laid to form a solid base on which to build. The walls were then built using a local brown stone we brought in, supplemented by a small amount of stone dug up during the excavation. We finished the top of the walls with hand split and dressed large flat coping stones and the curved steps with specially selected stone with the required curve.
Once the stone walls and steps were completed we cleared all the stone from the bottom level which was to be a large paved sitting area. A simple pergola was then constructed using green oak timbers, braced on the corners with traditional pegged mortise and tenon joints. We then spread a 75mm layer of crushed limestone scalping's which was then plate compacted to produce a solid base for the paving. We laid large pieces of hand split local stone up to a square metre in size laid in crazy paving style with the minimum of cutting to preserve the natural edges.The paving was laid on a 50mm bed of mortar and then pointed with a strong wet mortar pointing mix.
To complete the 6 month project we moved in 40 tons of topsoil to fill the terraced planting beds and topsoil the lawn area to be grassed on the top level. We spread the soil with an excavator, raked it to a fine finish and then seeded. The final touch was to lay a short stepping stone path linking our steps to an existing patio outside the upstairs sitting room French doors.
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