The Silva Cell works with all types of paving. During a recent webinar, one participant asked if settlement is a concern in areas where unit pavers have been installed continuously over both Silva Cells and the adjacent soil subgrade. Good question.

We have not experienced settlement in cases like these, but that’s not to say that it’s not a valid concern. We believe there are three keys to mitigating the potential for this type of settlement.

1. As with most cases when soil is involved, proper compaction is the key. Construction of a Silva Cell system is no different. The soil (backfill material) used to fill around the perimeter of the system between the frames and the walls of the excavation must be placed in lifts and compacted to the same standards as the surrounding hardscape area.

2. Another key factor is the aggregate section under the pavers. Our standard detail for when pavers are used calls for the pavers to be installed on a minimum of 300 mm of aggregate base.  In addition to increasing stability and load bearing capacity, this also helps ensure that the area directly under the pavers will be well drained and therefore less susceptible to the effects of frost.

3. The third factor is the layer of geotextile fabric that gets placed over the Silva Cell decks or between the decks and the aggregate that’s part of the pavement section. We recommend this fabric extend a minimum of 450 mm past the limits of the excavation/backfill area to create a transition zone that will help the pavement section bridge should there be any minor settlement of the soil beneath it.

If anyone would like to discuss this issue, or any other other construction-related questions further, please feel free to contact me directly ([email protected], or 612 840 9004).

Image: Mr. Mac2009