Masonry Magazine December 1994 Page. 19
Base: The Most
Critical Factor
for Success
An understanding and application of the proper methods for preparation and installation of base systems are the most critical factors in the success of paving stone and retaining wall installations.
HANDY-STONE retaining wall.
By LEN BROWNING
Creative Paver Marketing, Ltd.
The time and care that a contractor puts into the preparation of the base system of a paving stone or retaining wall installation is the most critical factor in establishing the success or failure of a project. A compacted road mix is the foundation for both interlocking paving stones and segmental retaining wall systems, and understanding the proper methods for its preparation and installation is critical.
The industry accepted and recommended material for base is called a 4-inch crusher run or grade "A" road mix. The following is a sieve analysis of the base material that is required:
Sieve size or
number
Percent Passing
34"
100
80-100
45-65
12
No. 4
No. 10
35-50
No. 40
No. 200
12-26
0-8
Once the contractor has found an acceptable source for base material, he should regularly monitor the quality of these materials. If you install road mix with too many large stones and not enough fines, the prepared base will form a rough surface with voids which will allow the bedding course of torpedo sand to migrate down into the base. Conversely, if the road mix is all fines and no large stones, the strength of the base is reduced.
An added consideration for the type of base material you choose, is the fact that some plants thrive in an acidic soil condition and as a rule crusher run does not affect the soil's PH, while many times grade "A" might. Investigate your source and learn the characteristics of your road mix.
Prior to installing the base material, it's important to insure that the installation plan consider proper drainage. grading and layout. The excavated area where the base is to be installed should be thoroughly compacted and sound. Should any organic matter be found, it should be removed, filled with appropriate backfill and compacted.
The thickness of the base material.
MASONRY-NOVEMBER/DECEMBER, 1994 19