Do-it-yourself Cantilever Retaining Wall
The Cantilever Retaining Wall System can improve the utility and beauty of your outdoor living environment, add to the value of your property, and can be constructed in 4 Simple steps.
1. Upright post Installation
Place a layer of coarse rubble at the base of the upright post for drainage. Stand posts in holes and brace temporarily. Check the alignments and ensure there is sufficient backward slope to compensate for deflection of timber or foundations under load. In most cases, a 5% deflection towards the retained load is sufficient. Use a string line to ensure proper upright post alignment. Use a string level or water filled plastic hose to correctly align upright post heights.
2. Concreting Posts
Ensure there is adequate space behind the posts to fit the horizontal timbers. Fill the post holes with concrete to just above ground level. This will prevent the pooling of rainwater around the posts.
3. Horizontal Timber Installation
Place the first horizontal timber behind the base of the upright posts. The most important step is ensuring this horizontal timber is level. Depending on ground surface, a small trench maybe required to achieve a level finish (a spirit level will give the most accurate reading).
Pre-drill a slightly undersized hole into the horizontal timber and drive the spike into the upright post. With the first horizontal timber now level and fastened, precision finish landscape products make the rest of the job easy.
THERE NEEDS AN EXTRA PARAGRAH HERE FROM THE IMAGE DOWNLOAD
To ensure proper drainage at the base of the wall, install a perforated polythene pipe along the back of the wall. The fall of the pipe along the wall should allow drainage at a suitable disposal point. Be sure to install a granular drainage layer behind the wall and around the pipe. A surface drain should be installed where the ground slopes towards the wall.
No. of horizontal timbers per m = 10. Table based on the use of 1OOmm diameter logs, slabs, winged splits or splits. Post requirements (i.e. spacing and anchoring) and diameter size of horizontal logs will vary depending on wall height, soil type, and the total load to be retained.
This is a guide only. Consult your treated pine specialist, a registered consulting engineer, and local shire council for design assistance and building requirements.
Heavy Duty Cribb Walls
These provide an attractive easy to construct retaining wall system suited for applications where ground conditions are not suitable for deep post embedment and soil conditions are suitable for cribb wall construction.
Cribb walls can be constructed from either slabs machined from logs ranging from 125 to 150mm diameter or landscape timbers. Stretchers are available in 2.4 and 1.8 metre lengths while headers are supplied in 0.6. 0.9 and 1.2 metre lengths. The correct choice of headers and stretchers for your particular application are dependent upon the height of the wall and the soil type. Please consult with your local stockist or professional tradesmen for more detailed design information.
1. Cribb walls must be constructed with a backwards lean (batter) of 1:4. A template should be prepared on which a spirit level can be placed to ensure the correct angle of the base and batter is maintained as the wall progresses.
2. Once the foundation stretchers are in position, the first layer of headers is placed in position at the correct centres. (See diagram A). Headers should be pre-drilled and secured to the stretchers by driving a galvanised bridge spike into stretcher. Each level must be secured in this manner as the wall progresses. Timber angle guides should be nailed periodically along the wall to ensure the correct batter is maintained.
3. Place backfill on a continuous basis as the wall progresses ensuring the backfill is sufficiently compacted. Ensure that each layer is filled and tamped down on an individual basis. Do not leave the backfilling until the wall is completed or the soil will not be sufficiently compacted.
4. The material used for backfill is very important. For 2.0 metre high walls, dense silt or silty sand can be used. For walls up to 3.5 metres, sand or gravel and sand is required to allow adequate drainage. Above 3.5 metres, clean gravel, sand or broken stone is required.
Half Round Logs for Decorative Walls
Decorative walls can also be constructed from half round logs as shown. (Design criteria for this information is based on slab rounds).
The diagram below shows three possible cribb wall arrangements. Consult with your stockist on the most suitable design to be used for your application. You will need to know the height of the wall, the soil type and the angle of the backfill slope. (Diagram C).
Cribb wall components are produced from logs which have been sawn on two sides to produce a parallel slab approximately 125mm in thickness.
In order for your supplier to assist you in accurately calculating the correct cribb wall design, it is important to know the angle of the backfill slope.
The diagrams below detail the layout of headers and stretchers for the three types of cribb wall construction, Types 1, 2 and 3. Once the wall type is selected, follow the layout pattern for the wall design chosen. For type 2 and 3 walls, 1800mm or 2400mm stretchers may be used.
WARNING: CCA treated timber must NOT be burnt for disposal. Burial of offcuts and shavings is the preferred method.