Retaining Walls

The most recently developed material for building a retaining wall is pre-cast interlocking concrete stone blocks (also called modular or segmental units) which lock together without using mortar. Materials and labor run anywhere from $15-$30 or more a square face foot, or around $750-$1,500for a wall 30 inches high by 20 feet long (50 square face feet). The more expensive blocks are stronger and will stack higher. Do-it-yourself materials cost about $10-$15 a square face foot. ThisOldHouse.com provides a video[1] showing how to build a block wall, calling the project "challenging" and estimating it will take two people 8-10 hours for a low wall 10-16 feet long.

Material and labor for a wood retaining wall runs approximately $20-$25 a square face foot (and there's usually a minimum charge for small projects), which would be about $1,000-$1,300 for a 50-square-face-foot wall. Plain lumber is vulnerable to termites and will rot quickly, so a wooden retaining wall is usually made of redwood, pressure-treated fir or used rail ties. Better Homes & Gardens provides do-it-yourself instructions for building a retaining wall of railroad ties or large timbers[2] or pressure-treated wood[3] .

Materials and installation for a stone retaining wall start around $25-$40 a square face foot and go up depending on materials, site conditions, and other factors. It costs $1,250-$2,000 or more for a wall 30 inches high and 20 feet long. Building a stone wall is as much art as it is science, and because it's hard to estimate exactly how much actual labor will be needed most contractors work on an hourly basis rather than for a flat fee -- so the total cost may fluctuate considerably, depending on circumstances. The Building Stone Institute explains how to build a stone retaining wall without mortar and ThisOldHouse.com describes the process for building a stone retaining wall with mortar[4] .

Poured concrete costs about $30-$40 or more a square foot (usually with a minimum charge for small jobs), or about $1,500-$2,000 for a wall 30 inches high and 20 feet long. ConcreteNetwork.com provides an overview[5] of the various types of poured concrete walls, while Better Homes & Gardens gives basic instructions[6] for pouring your own concrete retaining wall.