Retaining Walls – Overview
Retaining walls require thought and planning just like any other building project. Soil properties, drainage, surcharge loads (additional weight from objects placed on top of the ground above retaining walls such as cars and trucks), height of the wall, bedrock geology, etc. all must be taken into consideration. It really pays to do your homework, due to the amount of work and cost in building a retaining wall. Many fine publications are available that offer suggestions and design tips in constructing retaining walls. Several are listed here.
If you decide to construct a wall over 3 feet tall, give serious consideration to hiring an engineer to help you in the design of the wall. Many engineers often have designs they have created for other walls in your area. They do not have to start from scratch. Often they have to perform various simple calculations to ensure that the design will work in your instance. This service may only cost $200 to $500 dollars. That is a small price to pay for a wall that will not fail.
If you do obtain a plan or design and hire a contractor to perform the work, inspect the work daily to ensure that the wall is being constructed as the engineer intended. Take photographs of the steel before it is covered with concrete. Document everything! Be careful not to backfill the wall too soon!!! Masonry (block, stone or concrete) walls take a while to develop their strength. Often it takes weeks! Your engineer will tell you when it is safe to fill behind the wall.
Pay particular attention to drainage behind the wall. All walls should be backfilled with coarse gravel that drains quickly. Water must be able to drain from the back of the wall. Water is extremely heavy. If water is allowed to collect behind the wall, it just adds additional pressure which may cause the wall to fail!! Be sure to account for water drainage. Install a drain tile behind the wall at its base. Provide holes in the wall to allow water to easily flow to daylight. Do whatever it takes to get water away from the wall.