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Calculating Retaining Wall Materials

Discussion in 'Hardscaping' started by Inspira, Apr 7, 2009.

  1. Inspira

    Inspira LawnSite Member
    Posts: 39

    I'm a homeowner, tackling an above-average SRW project (in terms of sheer size). I know it's going to take me all summer and many beer/food bribes to get my friends over here to help. Anyhow...

    I have detailed plans drawn out (my wife is an architect) and know precisely how much square footage/cubic yards etc, I need. My question, though, is how much extra should I plan for? I know when, for example, laying tile, you account for 20-25% extra for cuts/mistakes, etc.

    Would buying 20% extra materials (blocks/gravel) be enough? I would like to avoid last minute delivery expenses/delays, but of course don't want to be stuck with a bunch of materials left over.

  2. mcwlandscaping

    mcwlandscaping LawnSite Gold Member
    Posts: 3,164

    I do very limited amount of hardscape work over the course of the year but if your planning on taking a long time to do your project, why not just buy as you go so your not dropping that much cash at once and if you ever need to move the material over the course of that time period, your not moving ALL of it around. Any extra you would need would be very easy to figure in towards the end of the project this way as well....

    I'm just stating this as if i was a homeowner in the same situation, that's what i would probably do in your situation.

  3. Danscapes

    Danscapes LawnSite Senior Member
    Posts: 331

    Depending on how good your wives "estimating" is, I think you should be safe with 10 percent overage. Thats just a general rule of thumb for me but its hard to say without physically looking at your project.
  4. Inspira

    Inspira LawnSite Member
    Posts: 39

    Thanks guys. I was actually planning on doing this in two separate (smaller) orders (one side of the driveway at a time) only because I don't think I have the room for all that block/gravel on site.

    Brings up another question though now that I think of it - do suppliers change product lines often? In other words, say I order half, then it takes me literally all summer to do the job (for whatever reason). Should I be worried that they will discontinue the style/model SRW blocks before I can order for next year?

    Oh and the "estimating" is all me. Wifey drew the plans - they're perfect. It's up to me to screw things up from here...

    But thanks again. 10% sounds reasonable - just trying to ballpark the entire project.
  5. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Posts: 6,417

    I love these "my wife does this" lines!

    just exactly, what kind of an architect is your wife?
  6. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Posts: 6,417

    Waste factor is based on YOU. We're professionals. Do this day in and day out. We factor a 10% waste for pavers. 10% for curved walls. You will have a learning curve :)

    0% for straight walls.

    0% for aggregate.

    In terms of suppliers changing product lines - most suppliers do not. But when they do it's because a) the manufacturer cut them off because they did not pay their bill. b) The friendly sales rep left one company and went to work for another, so the supplier switched lines because they're buddies with the sales rep. c) Supplier switched lines because of poor customer service and or quality from the manufacturer.

    Now, you need to ask yourself this: if I have 5 tons of left over aggregate, am I prepared, and how I will I move it off the property???
    Last edited: Apr 7, 2009
  7. Inspira

    Inspira LawnSite Member
    Posts: 39

    That's what my concern was - so I'll estimate on more than the 10% you guys use. I'm mainly concerned with the blocks rather than the fill - I have a spot in the yard that could use any extra gravel I had.

    Thanks for the input. Got some decent prices from local suppliers, looks like we're ready to rock. My back hurts already.
  8. GMTA

    GMTA LawnSite Member
    Posts: 68

    I imagine you were looking for a total cost in materials and that was the concern for how much more product due to waste/cutting especially since the wifey is involved and probably has the final say. :nono:
    If you factor in more waste for cuts on curves and much less if you doing straight runs like others have mentioned you will be more accurate.
    Since your doing this in two parts: Order as much as you think according to your estimates. This will be a great learning experience when it comes time to order for the next segment of the job in order to reduce the amount of extra material when everything is done. Also if you happen to have leftover materials the first time around it's not that big a deal because your going to be completing the next part of the job with the same materials. Your local supplier should be able to help you with calculations of materials needed if you provide measurements. (ie: WALL - trench width, length, depth of base material being used / PAVERS - sqft. of base, depth of desired base, as well as sqft. and depth of bedding sand.)
    Don't be affraid to ask questions when stumped so your not screwing yourself over with too much product, not enough product, silly errors in installations.
    Good luck and post pics!
    Last edited: Apr 7, 2009
  9. Inspira

    Inspira LawnSite Member
    Posts: 39

    As you can see, the wall is in pretty bad shape and seems like it will go at any time. The deadmen (at least the ones on top) are only a foot long, and the neighbors tell me that when they put this wall in, they didn't put any kind of drainage system behind the wall.


    The other side (which will be phase two, probably this fall) isn't leaning, but it's bowed out a bit, and the ground behind has settled almost 8 inches, taking my sidewalk and front stairs with it. Then of course the stairs are rotting.

  10. STL Ponds and Waterfalls

    STL Ponds and Waterfalls LawnSite Bronze Member
    Posts: 1,177

    I would do the sidewalk side first because you'll need to tearout the steps and walk to get grid and rock behind your wall and be able to compact it sufficiently.

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