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Retaining Wall System FAQs

Q – What thickness Stepoc and reinforcement bar should be used?

Answer. A – There are design charts in the Stepoc literature which are for guidance only at the preliminary stage. A full design check should be undertaken by the designer/structural engineer to determine the correct steel reinforcement.

Q – How high can I build Stepoc before filling with concrete?

Answer - The wall can be filled at any height up to a maximum of 2.25 meters (1.8m for 200mm units). If filling the wall in two or more pours the concrete should finish 50-75mm below the top of the block to provide a key for subsequent courses.

Q – Can Stepoc be constructed around corners that are not 90º on plan?

Answer - Yes this can easily be achieved by building the blocks square to the angle on the inside face and then forming a temporary shutter at the corner prior to pouring the concrete into the shutter. Steel reinforcement should remain continuous at this point. Alternatively the blocks can be cut on site to the required angle.

Q – What type of materials should be used to backfill?

Answer - Granular materials such as rock and sand are best if available. These types of materials compact fairly easy and won’t hold moisture that can increase the weight of the soil behind the wall. Keystone walls can be effectively build with silty materials and lean clays, but these types of soils require more compaction care should be taken not to place these materials when they are wet. Soils high in clay content and organic soils should be avoided.

Q – How often do I need to compact the fill soils behind a Keystone wall?

Answer – Compacting backfill material in 200mm – 300mm lifts allows you to effectively compact the entire area behind the wall without putting unnecessary pressure in the unit.

Q – When building gravity walls with terraces, what is the recommended distance between the terrace walls where the upper wall does not affect the loading condition of the lower wall?

Answer – The distances between terraces (face of wall to face of wall) should be greater than or equal to two times the lower wall height. Typically this can also work for lower height soil reinforced walls. With higher reinforced walls build on a slope, the issue of global stability must be considered by a qualified engineer in analysing the terrace situation.

Q - Can Stepoc be built to a radius?

Answer – Radius can be constructed from all three thicknesses of Stepoc – drawings are available to show the minimum radius that can be achieved without opening up the joint on the back face. Tighter radius can be achieved, however we would suggest calling the Technical department in the first instance.

Q – Is there any other way to place the concrete other than a pump?

Answer - Pumping is the easiest, quickest and cleanest method. If the wall is low enough, it may be possible to discharge the concrete directly into the top of the wall. Alternatively a concrete skip can be used, although this will require plant to lift the skip to the appropriate height.

Q – Can a vibrating poker be used to disperse the concrete around the Stepoc wall?

Answer – No a vibrating poker can cause stress in the jaws of the Stepoc wall, this risks cracking and displacement of the units. If the correct mix is used it should disperse easily without the need of vibration methods.

Q - What is the thermal conductivity of Stepoc?

Answer - The wall once in-filled with concrete will provide a Thermal Conductivity(k value) of 1.60 (W.m-1.K-1) (figure taken from CIBSE guide)

Q - How high can Keystone walls be built without the use of Geogrid?

Answer – Keystone walls can be constructed without Geogrid between 600mm and 1800mm high depending on the type of unit, soil conditions, degree of batter and surcharge on top of wall. Contact the Technical Department for further information

Q – Should I always begin construction at one end of the wall or is it OK to start in the middle?

Answer – Construction of the wall should begin at the lowest point wherever possible. If the wall is going to tie into a building or structure, measure the distance from the corner of the Keystone unit to the edge of the building and make sure the distance is in an increment of 457mm. (Full unit width).

Q – How high can Keystone units be stacked before placing unit corefill and backfill?

Answer – Keystone recommends adding corefill and backfill after each consecutive course for the Compac units. This insures that all voids are properly filled with rock providing maximum interlocking strength. It also aids in keeping the wall straight and reduces the amount of wasted rock.

Q - What colours is Slope-loc available in?

Answer - Slope-loc is available in three standard colours, Flint, Yorkstone and Sandstone. Other colours can be considered depending on volume required, please contact Sales for more information (01606 535300)

Q - What height can Slope-loc walls be built to?

Answer - Slope-loc can be built as an unreinforced wall up to 0.85m and above this the walls need to be reinforced

Q - Can I render directly onto a Stepoc Wall?

Answer - Yes, you can render directly onto Stepoc Blocks treating it as you would a normal concrete block.