The most important element in pavement construction of any sort is the base. This is the most crucial element that ensures the longevity of your investment by preventing settlement and increasing the lifespan of the finished surface. At Shanahan Consulting & Construction we recommend at minimum to our clients a 8” granular base of either crusher run or granular A, when crusher run is not available locally. Once properly compacted with both vibratory and static compaction methods to a minimum density of 98%, an application of a 2” bedding coarse that is free of any fines is applied for paver installations. The importance of a fines free bedding course it is assists in preventing frost heave and efflorescence from developing on the surface. The fines in a base material can also lead to premature stone failure due to salt getting trapped underneath the stones when the base does not drain correctly.  In driveway application we recommend a minimum total of 24” of base material with 16-18” of that total depth being a 2” stone which will stabilize better than traditional ¾” crusher run or granular A. A 6-8” layer of crusher run or granular A is then applied to obtain a more consistent grade. Each layer of base and bedding material must be properly compacted to prevent any settling to a minimum 98% density.

Geogrid when laid above the subsoil creates a stabilized based by the aggregate being confined within and above the geogrid which reduces both vertical and horizontal movement. The vertical and horizontal movement is created when a load is placed on the finished surface or from frost below. Geogrid can also be used directly underneath permeable pavers to prevent the pavers from shifting within the clear gravel underneath. Geogrid is also used as a tie back system to prevent walls from pushing forward when it is laid between the layers of wall material and extending behind the wall face.

Geotextiles also known as filter cloth is a useful element in separating the base material or backfill from the soil beneath or behind in wall applications. The use of filter cloth prevents the migration of small soil particles contaminating the granular base or backfill while still allowing the water to drain.  In areas of soil that silt or clay based over time due to rainfall the compacted base material will mix with the compacted base and weaken the paving system. The installation of filter cloth will prevent this mixture from happening when placed above the native soils before the placement of granular base. This procedure creates a barrier between the soil and the granular base allowing the water to still be shed from the area and preventing the soil from working its way into the base. An application of filter cloth just above the subsoil it also creates a bridging affect that assists the geogrid layer in reducing both the vertical and horizontal movement of the granular base. This is why at Shanahan Consulting & Construction we always recommend the placement of both materials, especially when you have clay or silt soil or for driveway applications.