How deep do footings have to be for a retaining wall?

Question

Are there any retaining walls that do not need cementing?

Answer 1

rule of thumb for depth is a third of what it is retaining, ie, 2m high then it should be 1m deep. This of coruse depends on the type of ground. a good tip is to leave weep hole for water, this wil lstop water pressure building up behind it.

this would work with steel sheets or a steel reinforced structure.

If you wanted to use stone or brick, then you should make the wall heavier than what you are retaining, ie, soil has a density of about 1.7 metric tonnes per m3, concrete has a density of 2.4t per m3. Therefore for a 2m hight wall, pressure at the bottom would be 3.4tonnes per meter run, so if you put 3.4t of concrete in front if it it should hold, but, really you would want more to be safe, say 4tonnes per meter. Other considerations would be to toe in the wall or have a caterliver wall etc etc.

Another method you could use is soil geotextiles, however, this would require earth moving, they work by having netted sheets of plastic and burying them in the soil.

Answer 2

that depends on where you are and the local building codes, but it definately has to be below the frost line, assuming it's a "wet" wall. if the wall is laid up without mortar it's only got to be about 8" deep, but that limits the height that the wall can be. A dry wall usually shouldn't be more than 2 or 3 feet above ground.

Answer 3

Depends on your climate and how high your wall will be and what it will be retaining. Most wall failures are directly related to poor foundations. You'll need to contact your local regulations on that.

As for not needing cementing, a dry stack wall will qualify:
http://landscaping.about.com/cs/lazylandscaping/ht/retaining_wall.htm

Have you looked into the new interlocking blocks? These are amazingly strong (yes, they need a foundation).

Answer 4

Footings generally work best below the frost line. Especially if there will be a lot of horizontal pressure. If you are only talking a foot or two in height of the wall you could lay them without a footing but in years to come be prepared to rebuild all or part of it.

Answer 5

Look at http://www.pavingexpert.com/featur03.htm#retain

Also, after reading my dry-stone walling book (yawn), yes you can do retaining walls without cement. Unfortunately there's too much info to put here so you need to buy a copy.

Answer 6

Depending on where you live the general rule is 36 inches. The footing being below the frost line is what prevents heaving when you have freezing and thawing of the ground.

Answer 7

You might save yourself a lot of trouble by calling up the zoning authority and asking them. While you can over-build without a problem, if you under-build, you might be ok but when and/or if you decide to sell, it would be undoubtedly inspected and needed to be brought up to specs before you could sell it. That's where contractors come in. They know the local laws and what they can and can't get away with.

Answer 8

ep henry