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Residential Retaining Walls

Discussion in 'Residential Foundation Codes' started by globe trekker, Jun 1, 2011.

  1. globe trekker

    globe trekker Sawhorse

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    In looking at Section R404.5, [ `06 IRC ], anything over 24 inches in height

    would require "some type of design".

    Is this saying that if a residential landscaping feature; retaining more than

    24 inches [ vertically ] of unbalanced fill, will require an RDP design before

    being installed ( i.e. - landscaping timbers, ..railroad crossties, ..masonry

    or stone products )?

    The conundrum: The female of the house "desires greatly" to have a new

    flower bed put in. She also "desires greatly" to have this new flower bed

    to be elevated [ Ya know, so the whole neighborhood can see it ].

    Because of the existing slope of the yard, she wants it to be at least 3 ft.

    high in places. According to Section R404.5, a "design" is required to

    prevent overturning, ...ensure stability, blah, blah, blah. However,

    Section R105.2, # 3 exempts retaining walls not over 4 feet in height,

    " ..unless supporting a surcharge." What's a surcharge?

    What is the correct application here? Am I going to have to have some

    designed plans drawn for this new flower bed? Thanks! :eek:

    .
     
    #1 globe trekker, Jun 1, 2011
    Last edited by a moderator: Jun 1, 2011
  2. FredK

    FredK Gold Member

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    Yes, no and maybe. Since I stayed at a Holiday Inn here's my engineer's interp.

    Surcharge is basicly a load that could be imposed on the wall.

    Here's how I explain it:

    Say a retaining wall is 8 ft tall and you desire to place a building footing on the wall (think that looks like the back wall of a basement). The earth and water (when it rains) puts a force to topple the wall inward. Same goes for any load that could put a force on the wall causing it to tople over.

    So how far back would a pool/structure have to be to prevent a surchage? In old days if you left land to form a slope naturally it would finally balance out at about a 45% angle. So if you go up 2 ft high the structure would have to be 2 ft away to not impose a surcharge. 4ft high 4 ft back, etc.....

    As for a flower bed depends on where you place it and what damage it could do to the existing foundation/footing of your house may be different from one area of the country to another. (Got to love Mike Holmes for showing flower beds next to homes with basements up north and the damage it does.)

    Just my 2 cents.
     
  3. mark handler

    mark handler Sawhorse

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    AS FRED SAID "Surcharge is basicly a load that could be imposed on the wall"

    Surcharge is a load imposed on the retained soil that may impose a lateral force in addition to the lateral earth pressure of the retained soil.

    Examples of surcharges are:

     Sloping retained soil

     Structure footings supported by the retained soil

     Adjacent vehicle loads supported by the retained soil

     Solid fences that are attached or directly adjacent to a retaining wall when wind pressures act on the fence
     
  4. lpoplar

    lpoplar Member

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    I have to agree. I also understand the part about the surcharge like this.

    I think flower beds aren't a bad thing. Plants and the natural spaces in general make a neighborhood more worth living, don't you think? I made a small garden with flowers by post from uk which I got as a present in my frontyard and I always get compliments from my neighbors!
     

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