NEW RETAINING WALL - HOUSE GROMER

NEW BLOCK RETAINING WALL REPLACES LOG STRUCTURE

March 2014, Nr 2 Orchard Valley, Brackenridge, Plettenberg Bay.

We replaced an old log wall with a brand new concrete block retaining wall. Once again the block of choice was the Sholin Rock Face block to match the existing blocks on the property.

Specifications:
20 MPA concrete foundation 750mm x 230mm
Subsoil drainage system behind foundation blocks
Blocks filled with hand tamped topsoil
Imported free draining filling sand, 300mm wide behind wall
All fill behind old structure to be removed stockpiled and replaced and compacted with rammer

During the demolishing of the old structure we discovered that all stormwater outlets and subsoil drain pipes were discharging behind the log wall. Because the back fill behind this wall was done with clay it trapped this water and caused the poles to rot. We extended all these pipes and repaired damaged ones to discharge in front of the new block wall.

On completion new plastic sheeting was purchased and placed before the stone chip was replaced.

CREATIVE DRIVEWAY WALLS

It is always such a pleasure doing work for awesome clients. The owners of erf 8463, Brackenridge, are awesome people.

The client asked us to tidy up the entrance to his property with some retaining blocks. We used the Sholin Rock Face block to match the existing blocks previously installed at the property.

The founding depth for the walls was 600mm into natural ground. We started off with a 750mm x 300mm, 6% stabilised SSG footing. The blocks were placed on this base with a subsoil drainage system directly behind the foundation blocks.

We filled the blocks with hand tamped topsoil and a 300mm wide free draining back fill were placed and compacted behind the blocks. The void between the paving border and retaining blocks were filled with concrete and schemed afterwards.

REPAIRWORK ON A TERAFORCE BLOCK RETAINING WALL

A section of retaining wall on the boundary failed and posed a safety risk. There could be a number of factors which could have contributed to this event, namely:

a) Soil erosion behind the retaining blocks caused by fine dune sand seeping through the blocks. This erosion can be caused by storm water running over or behind blocks or by wind erosion. Gravity retaining walls relies heavily on the weight of the filling in the blocks to retain stability.
b) The section of earth behind the retaining wall that was filled above the natural ground level and the additional weight of the blocks, including blocks on the neighboring property to retain this fill, created a load in excess of what this most basic design could handle.

The following steps were to taken to remedy the situation:

a) The blocks on the affected section of wall were removed and stacked aside. This included the section of blocks on the neighboring property. All excess soil was removed and stockpiled for refilling afterwards.
b) A concrete foundation have been cast, kicking unto the house foundation. Y12 steel reinforcing starter bars were inserted into foundation and spaced 400mm apart. This reinforcing extends through the blocks filled with concrete for the first 1.5m.
c) Additional blocks were filled with topsoil.
d) The sand replaced behind the retaining wall was stabilized with a 3% cement mixture.

Erf. 8354 Brackenridge, Plettenberg Bay, South Africa

This wall was built with the tan colour, rock face block from Sholin. Sholin manufactures these blocks in Knysna, South Africa.

The home, for owners Mr & Mrs Leary, was constructed by SGB Construction ( Steve Brown ), a local company from Plettenberg Bay.

The founding depth of this wall was 500mm below the finished driveway level. No concrete foundation were cast, but a 250mm deep, stabilised, well compacted SSG footing was used instead.

A subsoil drain was installed behind the wall to prevent ground water from seeping through the blocks and staining the paving blocks in the process.

The blocks were filled with hand tamped topsoil. All the back fill were compacted in layers not exceeding 160mm by rammer.