View Full Version : Calculating Retaining Wall Materials

04-07-2009, 11:15 AM
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.


04-07-2009, 02:45 PM
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.


04-07-2009, 03:41 PM
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.

04-07-2009, 04:35 PM
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.

DVS Hardscaper
04-07-2009, 06:00 PM
I love these "my wife does this" lines!

just exactly, what kind of an architect is your wife?

DVS Hardscaper
04-07-2009, 06:06 PM
........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.

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???

04-07-2009, 06:49 PM
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.

04-07-2009, 07:44 PM
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!

04-09-2009, 11:38 AM
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.


STL Ponds and Waterfalls
04-09-2009, 04:51 PM
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.

04-09-2009, 05:23 PM
I'd love to do that side first - but there's a very good chance I'll only have the money (and energy) to do one side this year - and I'm afraid of going through one more winter with the other wall leaning like that.

Then again, I've gotten some great price quotes on block, and may be able to do it all at once. Will still do it in two phases though, only because I don't have the space on my property for all the fill/pallets.

04-09-2009, 05:37 PM
I see from your pics your located in NJ. Where abouts? I would be more than happy to come by and do it for the right price......

According to your pics it doesn't make sense that this will take you all summer to do one side of the drive (even if your just an inexperienced homeowner). Make sure you factor in renting a skidsteer to move things around. This will help move your materials around, speed up the installation process and alleviate some strain on your body.

04-09-2009, 06:05 PM
Is that wifey-the-architect's "detailed plans" there on the legal pad?
(if so I would add another 50% in extra materials)

04-09-2009, 06:54 PM
I got plenty of prices, it's just not in the budget. Believe me, I'd love to pay 10-20K to have a pro do this. I'm a web designer, not a landscaper. My hours limit me to pretty much weekends, unless I take a week off completely - which isn't in the cards right now because I'm working on a lot of projects.

We'll see. I'm taking it one step at a time.

Once again, appreciate all the input (even the wifey remarks).

04-09-2009, 10:14 PM
whats under those stairs? you may open a can of worms when you pull that wall. once you get the base set it goes quick from there. you are going to move alot of material and your gonna want atleast a bobcat to help back fill that wall. you will need a plate compactor as well. i hope you have the equipment or atleast access to them. or 5 years from now you wall is going to look the same. and dont use gravel behind the wall.

04-09-2009, 10:18 PM
Ok well good luck on the project.

Just a thought....most of the time getting someone to do it right the 1st time, or paying a professional, saves you money from improper installation or lack of experience or whatever you want to blame it on later on when the wall is leaning in or sagging in places or ends up looking like your current RR tie walls.

For your sake and budget do it right the 1st time regardless of the extra time, energy, money, inexperience, etc....

Cheers to you and your helpers!

04-09-2009, 11:19 PM
under the stairs is a family of chipmunks!

i'm renting a plate compactor from a local tool rental place, and I have a guy coming with a bobcat to do most of the demo/digging out.

make no mistake - this will be done right. it's just going to take me a little longer than you pros...the first few years of living in this house have been spent fixing things the prior owners thought they were taking care of. i'm a big proponent of doing things once and doing them right.

so, uh, does anyone in the north jersey area need some slightly worn railroad ties? lmao

04-09-2009, 11:31 PM
so, uh, does anyone in the north jersey area need some slightly worn railroad ties? lmao

:laugh: now that is funny!

04-15-2009, 02:47 AM
Be sure if you do have to order your blocks in different orders, try to limit it to two orders. One order for each side of the drive. Point I am trying to make is if you order one pallet, do a couple courses of the wall, then another pallet, they make be slighty a different color and you may notice it once the wall is finished, each course having a different shade. Best thing to do is order all block for each wall at the same time then just take blocks from each pallet as you go, mixing them all in.

Good luck with the project.

04-15-2009, 11:28 AM
To be honest that looks like a pretty easy and straight forward project. Now don't get me wrong the sides with the steps might give you some aggravation because you might have to dig back a long ways to get a good base. If your going to do this yourself then I would start with the wall to the right of the garage just to get the hang of it. Also do not, I repeat do not drain that downspout through the wall or above the wall, pipe it out to daylight as far as you can get it.

04-15-2009, 12:51 PM
Thanks again for the input. About the downspout - I plan to drain it behind the wall, out to the street, but in a separate tube. In other words, I'll have the perforated 4" drain pipe at the bottom of the wall in the gravel, but then higher up, maybe only a foot or so below grade, I'll have a solid 4" pipe carrying the rain water. I won't have this separate tube in the gravel, but behind it, this way I still have the 12" of backfill.

04-15-2009, 06:51 PM
why not 90* it straight to that little patch of woods? Less work and less chance of couplings failing behind the wall.

04-15-2009, 09:38 PM
That little patch of woods is nothing more than a few bushes - just past it there is a sharp decline down to my neighbor's house. They have enough water problems as it is...lol

Most people on my street just have the downspout come straight down into the driveway, but I'm the only house the driveway pitches TOWARDS the garage instead of away. Funky hills on my block.

11-12-2009, 05:24 PM
those aren't railroad ties...they are 6x6 pressure treated lumber.

11-12-2009, 07:11 PM
how'd the project go?

11-12-2009, 10:55 PM
Never got off the ground. I work for a firm in the mutual fund industry, so this summer was, well, pretty interesting. For a few months I wasn't even sure I was going to have a job, and couldn't justify dropping several thousand on a wall. We'll try this again in the spring...