Trench Sheets

The primary difference between overlapping and interlocking trench sheets lies in their joint mechanism. Overlapping (or lapped) sheets simply rest over one another and are ideal for standard soil retention. Interlocking sheets, such as the SEI profile, feature a mechanical clutch that physically links the sheets together, providing superior structural integrity and a barrier against groundwater ingress.

The main methods of trench sheet installation are the "push and dig" method and the "pre-drive" method. Push and dig involves pushing the sheets down progressively as the trench is excavated, which is highly flexible around existing underground services. Pre-driving involves using piling hammers or vibrators to install the sheets to their full depth before excavation begins, ensuring maximum wall stability in difficult ground.

For excavations in water-bearing ground, the best trench sheets are interlocking profiles, such as our 6.0mm SEI Interlocking Sheets. Because they mechanically link together to form a continuous wall, they provide a much tighter seal against groundwater and fine soil seepage compared to standard overlapping sheets. Interlock sealants can also be applied for enhanced watertightness.

You should choose the correct trench sheet by evaluating your specific excavation depth, soil type, and groundwater levels. Standard 3.4mm sheets are suitable for shallow trenches in stable ground, while deeper excavations or high lateral earth pressures require heavy-duty 8.0mm profiles like the KD6. If water is present, an interlocking SEI sheet is necessary. Our engineers can provide BS 5975 temporary works designs to specify the exact profile you need.

Yes, under the CDM Regulations 2015 and BS 5975, if an excavation requires support, that support system must be formally designed and checked. There is no blanket minimum depth exception; any use of trench sheets is considered an engineered solution that must be specified by a competent Temporary Works Designer (TWD) to withstand site-specific soil and water pressures. Here at SEL we can supply both the sheets and the in-house temporary works design to ensure your shoring solution is fully compliant and safe.