How much do they cost?
Prices start at $4.30 per square foot for poured concrete, $5.65 for interlocking concrete block, $6.15 for pressure-treated pine, and about $11 for stone. Installation or supplies, such as drainage stone or filter fabric, are not included.
How long will they last?
Timber can last up to 40 years; there's no limit on the life span of a properly installed masonry or concrete wall.
DIY or hire a pro?
Timber and inter-locking-concrete-block walls are DIY-friendly. Mortared masonry and poured concrete ones are usually best left to a mason.
Does height matter?
Codes mandate that walls taller than 4 feet be designed by an engineer and built by a professional.
How much care?
Other than an occasional clearing of the weep holes, retaining walls don't need much attention.