 Concrete will need to be poured to surround the trench drain so that the load can be transferred from the channel and grate to the surrounding areas.Pre-cast trench drains generally come in 4-inch widths but can range anywhere from a 1-3/4-inch slot to 2-inch-wide channels with grates, and up to any size imaginable through custom trench drain divisions.A home owner could consider a pre-cast trench for a landscaping project as there are many pre-cast trench drain systems being manufactured specifically for the residential market.