I get this question asked alot, since the use of sheet piling in the form of temporary or permanent works, is well established for steel but not so for plastic. On one hand I believe with the range of plastic sheet piles we have now, we can offer an excellent solution to the construction of basements, but on the other hand it is not a core application that we have much experience with.
What I mean by this is that we have proven that plastic piling is fantastic for permanent retaining walls, bank stablisation, water control cut-offs or flood defences, but none of these applications are of a temporary nature, we only sell plastic piling we do not hire it out and so if considering this option you need to balance this against the cost of hiring in steel trench sheeting from Mabey Hire, MGF or Shore and Pour.
These Companies are more experienced in this type of application, shoring or temporary works and can often produce you a working design with their products. Further as stated their products can be hired or purchased and so you have a degree of flexibility here that I cannot offer you.
The main area where we lack experience is that in the construction of an excavation, it is normal to drive the sheets fully, the length reflecting the excavation depth and a toe. The toe is of a depth either matching the depth of the excavation or relatively shallow allowing for the use of other proprietary equipment - such as frames and struts.
The excavation is then dug out and work continues from this point. See the 4OD Underground house for an example of this.
Now the area that concerns me is the excavation against the plastic piles, in that during this dig out phase, the excavator can gouge out the plastic piling, whereas with steel it may scratch or at worse dent. Our main stream application involve driving sheets, but never secondary excavation and so I do not know how well the Plastic piles would perform when used in such away.
It is also common in temporary works design to produce a non cantilever solution producing a design encompassing struts and frames as well as the sheets, such designs get away with very shallow toes - say 0.5 - 1m, as concrete is often cast against them, and until the concrete is set the full proprietary system supports the excavation.
In permanent applications with plastic piling, say for instance retaining wall, we routinely use quite substantial toes, for example a 2m retaining wall would have at least a 2m penentration below ground, so use a 4m pile. Many contractors, would insist on more say 2/3rd into the ground, and so a 6m sheet.
APE does not produce working engineering designs and does not supply other proprietary equipment (frames or struts) and so we cannot advise in total what you would need.
So for this reason we would refer you to conventional steel trenching or plastic piling from these suppliers as they provide the full package.
Remember even if you do use steel sheet piles or trench sheeting, APE can still hire you the piling equipment to install it. 80% of our hire business is still installing steel piles or trench sheets.