If your future walkway or driveway is higher than the sides, DO NOT USE plastic edging or pre fabricated borders, nor stacked retaining wall with INTERLOCKING BLOCKS. All these will create problem in short period due to frost movement, soil type and drainage of area.
Usually Driveways require minimum 18 inches of excavation, walkways and patios 12 inches. If clay or silt present, installation of geotextile fabric (membrane) is must. By the way membrane is not for preventing weed growth. Also filling joint of the pavers with polymer sand is not a permanent solution it is only good for 2 to 4 years depending on grade, drainage of surface and precipitation amount. After all polymer sand is epoxy base sand which it will wash away on long run, when dry it is hard, when moist or wet then flexible and gels like. All we say it needs maintenance; there is no such a thing as maintenance free when we have deep frost and large temperature variation. Warmer weather does not give us this much trouble.
Retaining wall or structural walls: Depending on the situation and usage, for garden or landscaping, manufactures recommendation is valid to an extend depending on the height of the wall. When used to retain side of driveway, walkway or patio and or balcony, manufactures recommendation does not apply presently till the day they modify their techniques or (only applicable to warmer weather with no frost movement). There are situations that a geogrid can be used to stabilize the wall to an extend, this all depends on the contractors level of comfort in doing proper job. We do not recommend simple stacking of block on compacted gravel base adjacent to driveway in order to support the weight of driveway and vehicles to top, and or an interlocking paver walkway to close to wall. Many of our retaining walls have 18-24 inches concrete footing and walls are done masonry in order to give longer life span. This is mainly when we support a walkway, balcony or driveway on top. One main key important factor in any case is a well drained wall, with good drainage system behind the wall. For a long lasting wall and a better construction call Pavcan for free estimate and recommendation.