Step by step guide to building a Freestone ECO retaining wall
Freestone ECO retaining walls are suitable for most retaining or garden wall situations.
Each Freestone ECO block has self-locating lugs which easily lock into the block above to provide a vertical wall. Purpose made 90 degree corner and bullnose capping are available to provide a complete system. Freestone ECO blocks have a minimal setback which allows all available space to be utilised to the maximum. The large sized hollow blocks allow for steel reinforcing and concreate core fill where required, providing an earthquake resistant wall which can also accommodate fences and services.
There are two high quality surface finishes available, a smooth finish and an exposed aggregate finish. To enhance the unique surface finish and highlight the glass aggregate features, Freestone ECO can be sealed with a proprietary masonry surface sealer.
The Freestone ECO Retaining wall system can be built using three different construction methods.The most suitable method to build the Freestone ECO wall is always selected with consideration to the overall wall height, soil conditions and any loads that impact on the retaining wall such as vehicle traffic, fences or steep slopes.
OPTION 1 – Backfilled with 300mm wide blue metal drainage layer
This is the common method for building low non load bearing gravity garden wall. Freestone ECO blocks are built over a compacted gravel footing on a 25mm sand bed; all blocks are filled with 20mm blue metal. An ag-pipe drain is set up at the back of the wall base and then subsequently backfilled with a 300mm drainage layer.
Suitable for low walls dependent on soil conditions and any loads.
OPTION 2 – Backfilled with no-fines concrete drainage layer
Per option 1, Freestone ECO blocs are built as a gravity wall over a compacted gravel footing on a 25mm sand bed. However, to increase the strength of the wall and therefore build higher walls, the blue metal block infill and drainage layer in option 1 is replaced with a ‘no-fines’ concrete mix which both strengthens and increases the mass of the wall. The ‘no-fines’ concrete still allows water to flow into the drain below.
Suitable for walls up to 2 metres high subject to engineers design.
OPTION 3 – Reinforced and concrete filled on a concrete footing
Freestone ECO blocks are built on a reinforced concrete footing. The Freestone ECO blocks are simply stacked together and reinforced with horizontal and vertical steel, placed in the purpose made locations within the blocks. The blocks are then core filled with concrete to form a reinforced block retaining wall, without the use of mortar.
Suitable for walls up to 3 metres high subject to engineers design.
STEP 1 – Base Preparation
Dig out trench approx. 250mm deep. The trench should be 600mm wide. Place and well compact 150mm to 200mm of fine crushed rock (gravel). This base thickness depends on the wall height e.g. 200mm thick or 1 metre high, extra thickness for higher walls may be required, subject to engineers design.
STEP 2 – Sand bed
Spread 25mm of either sharp sand or metal dust over the compacted base. This should be in a straight line and checked with a level. If the wall is stepped, start at the lowest point.
STEP 3 – Laying 1st course
The first block course is not bedded into the sand bed. The use of a level and string line is recommended to ensure that the first course is laid correctly. For walls up the 1 metre high, make sure at least 100mm of the first block course is buried below the finished ground level. Allow approx. 200mm for walls over 1 metre high and 300mm for walls over 2 metres high. Compact gravel along the front of the blocks to stabilise.
STEP 4 – Drainage & backfill
Place PVC ag-pipe with a geotextile sock drain behind the wall, with a 1 in 100 fall. Backfill behind the blocks 300mm wide, with clean, free-draining material (E.g. 20mm blue metal) Ensure that each block is also filled with free-draining material. Backfull behind the drainage layer with your chosen backfill material in a maximum of 200mm layers. Compaction rate of 95% must be achieved (use only hand operated plate compactors close to wall). Do not use soft or wet clay to backfill. Be careful not to mechanically compact too close to the wall.
STEP 5 – Laying additional courses
Lay the next course and subsequent courses to a string line following the same procedure, as outlined previously, ie. clean the top of the blocks, fill the block cores and form a 300mm drainage layer behind the blocks, backfilling in max. 250mm layers, as per step 4. Ensure backfill is compacted to 95%. Corner blocks require adhesive fixing with Landscape Liquid Nails or Anchorloc 2-part epoxy.
STEP 6 – Laying capping units
Once backfilling and cleaning is completed as per step 5, fix the purpose made Freestone ECO capping blocks with adhesive. Landscaping Liquid Nails or Anchorloc 2-part epoxy is recommended.
STEP 7 – Sealing
To enhance the unique surface finish and highlight the glass aggregate features, Freestone ECO blocks and capping can be sealed with a propietary masonry surface sealer. There are two high quality finishes available, a smooth finish and an exposed aggregate shot blasted finish.
Smooth Finish – sealing is recommended
Exposed Aggregate Finish – sealing is optional only
Maximum Wall Heights for Freestone ECO Block Retaining Walls
Table 1 – Maximum wall heights for Freestone ECO gravity retaining walls, backfilled with a 300mm blue metal drainage layer.
Table 2 – Maximum wall heights for Freestone ECO gravity retaining walls, backfilled with no fines concrete to the specified width behind the wall.
Table 3 – Indicative wall heights for Freestone ECO retaining walls, laid on a reinforced concrete footing and reinforced with vertical and horizontal steel as specified.
Soil type descriptions
Type 1 soils – includes soft and firm clay, fine sands, silty clays. Internal Friction Angle > 20 degrees – 24 degrees
Type 2 soils – includes stiff sandy clays and gravelly clays. Internal Friction Angle > 25 degrees – 30 degrees
Type 3 soils – includes FCR, rock, sandstone and gravels. Internal Friction Angle > 30 degrees +
- The following assumptions have been made regarding soil properties:
- Infill Soil Types – As above: internal friction angle > 20 degrees – 30 degrees +
- Bearing pad
- Compact density angle : at least 18.6kg/m3
- Effective internal friction angle: at least 37 degrees
- Effective cohesion: at least 5kPa
- Caution is required when using heaving or dry clays as retained soil or backfill
- Surcharge loads are as follows
- Domestic vehicles – 500kg/m2 (5kPa)
- Heavy vehicles – To be separately assessed
- Drainage shall be supplied in the form of a slotted PVC ag-pipe with geotextile sock drain (fall at 1:100 min. to S/W disposal system) or with weep holes. A 300mm drainage layer shall be provided behind the wall.
- Table 1 gravity wall design table should be used for low, non-structural garden walls only.
- Wall embedment is critical, ensure embedment parameters are followed and compacted fill is places in front of wall.
- For backslope conditions greater than 1 in 4, seek specific engineering advice. Vehicle traffic should be allowed no closer than 1 metre behind the wall.
Engineering – To comply with most council requirements, please seek specific engineering advice for walls over 1 metre high or for low walls carrying vehicle traffic. etc.