It is a given fact that excavations and trenches backfilled with native soils will subside over a long period of time if the soil is not mechanically compacted. This is true in both summer and especially winter conditions. Compaction involves placing backfill material in layers known as 'lifts' and compacting each lift prior to the addition of the next lift

Keystone began offering compaction to the Calgary residential building industry in the early 1990's. Long a standard in the commercial construction industry and having witnessed the effects of settlement on builders and their customers, it became apparent that the subject of compaction needed to be raised. We began experimenting with compaction in an effort to minimize settlement in landscaped and concreted areas around new homes. Our success in this area has now convinced several of Calgary's most prominent builders to include compaction not only as a value added service, but as an essential service.

Successful compaction requires proper soil conditions, moisture content, air temperature, equipment, and trained equipment operators. The degree to which compaction is actually working, can be measured by a procedure called a 'Proctor Test'. This test enables trained technicians to evaluate field densities as a percentage of maximum density as determined for a given soil in a laboratory. Having established a laboratory reference, various field devises can be calibrated to the reference and used to analyze field results. In the commercial industry, landscaped areas usually require a 95% proctor density. Structural areas usually require a 98% proctor density. Guaranteed compaction requires compaction testing, however, based on our success to date and the added cost of testing, most builders and private home builders have elected not to test compaction in non-structural areas.

For winter backfilling, where there is not a sufficient amount of unfrozen material available for proper compaction, foundations and service trenches are backfilled without compaction. The following spring, once there is no longer any evidence of frost, we do what we have termed a 'surface compaction'. This involves compacting the surface area prior to and after completion of the lot subgrade. This action, although not as successful as compaction at the backfill stage, has shown to be quite effective in reducing costs in settlement repair.

Keystone now has over 10 years experience with compaction in both commercial and residential applications. Based on this experience, we believe that the most effective and efficient method of compaction available today is the use of hydraulic vibratory plate tampers mounted to excavators and tractor backhoes. Access with this larger equipment to back and sideyards is limited in some instances, however, these areas can be compacted using manual equipment if so desired. The critical areas for compaction are the interior and exterior of the garage, driveway and front yard where service trenches usually enter the home.
The bottom line is that the advantages of compaction far outweigh the disadvantages when considering the end result in both the short and long term.
Advantages include:

• less money spent on landscape repairs,
• less time spent dealing with deficiencies,
• less chance of moisture penetrating the underside of the foundation,
• less chance of foundation failure,
• less inconvenience by both the builder and customer,
• the ability to pour slabs immediately following backfill, especially important late in the construction season,
• and above all, a happier customer.

Choosing not to employ compaction only defers what is usually the inevitable. It is a typical 'you can pay now or pay later' scenario, only 'later' usually involves a lot of unnecessary grief for both builder and home owner.

So, why settle?

Ken Elias
President
Keystone Excavating