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View Full Version : Best way to level the base for SRWs


S&S Outdoor Services
12-28-2009, 02:43 AM
I have some experience with retaining walls but it seems to take forever when we're doing the base layers. Does anyone have some tricks to get the gravel as level as possible so it doesn't take so long? Thanks in advance for the help.

stuvecorp
12-29-2009, 07:40 PM
I use 4" poly concrete forms, set them with the laser and then screed a real thin layer of sand over the base course and then just set the block. It works for me but I don't know anyone else that does it like this.

Moneypit
12-29-2009, 09:14 PM
I leave my base about an inch or so high after compaction. Then my helper stays ahead of me with a laser level scraping the base level as I am installing the 1st course.

csl
12-29-2009, 11:04 PM
get yourself i really good laser or transit. ours is self leveling and is good to 1/8" at 500'. this will cost you $1200 or so, but on one big job you make it up on labor. NEVER use sand over your base rock to get level. you will have horrible settling and if the block manufacturer or supplier sees this they wont be happy.

stuvecorp
12-29-2009, 11:32 PM
get yourself i really good laser or transit. ours is self leveling and is good to 1/8" at 500'. this will cost you $1200 or so, but on one big job you make it up on labor. NEVER use sand over your base rock to get level. you will have horrible settling and if the block manufacturer or supplier sees this they wont be happy.

You will not have settling as the sand is less than a 1/2" at the deepest. I got the idea from my block manufacturer.

S&S Outdoor Services
12-29-2009, 11:47 PM
I have also heard it's alright to use an inch of sand or less to get the blocks level. I've been interested in using the method that Stuvecorp is talking about but have never seen it done. Could you go a little more in depth with that? Also, we are planning on spending around $1200 or so in the spring once we start getting some more hardscaping jobs. Thanks for the replies guys.

Bru75
12-30-2009, 12:04 AM
get yourself i really good laser or transit. ours is self leveling and is good to 1/8" at 500'. this will cost you $1200 or so, but on one big job you make it up on labor. NEVER use sand over your base rock to get level. you will have horrible settling and if the block manufacturer or supplier sees this they wont be happy.

Both versa-lok and techo bloc recomend a sand leveling bed, techo bloc even sells a special screed system for this purpose. If I recall correctly, the instructor for my NCMA class also said it is ok.
The trick is to get the gravel compacted and level so that the sand layer is kept pretty thin. If the compacted gravel is level and the sand bed is thin and uniform, you won't have any settling problem.

stuvecorp
12-30-2009, 01:02 AM
I'll try to find some pictures of the forms from a job. The forms are 15' long and are bendable so most sweeping curves can be done. They have clips that twist in a channel and a regular concrete stake goes through to hold it. I tried regular steel forms and it didn't work so great but love the poly ones. The cool thing is you can cut them to any size. I got them from Farrell Equipment.

I have been told and have never done it, that you could pour concrete for the base if you wanted. I wonder if there would be any time savings or if the concrete would cost too much?

S&S Outdoor Services
12-30-2009, 01:05 AM
I've also heard you can do a concrete base but it's supposed to only be one inch so it stays flexible. Maybe if you screed the gravel, pack it and screed a thin layer of concrete over the top...??

shethinksmytractors_sexy
12-30-2009, 05:37 PM
never use a concrete footer for a srw. that is just not going to work and plus cost will be alot more than gravel. after i excavate for the footer i set in rebar stakes every 6 ft. or so, using the transit each one is set at the desired height where they are all level. then put gravel in 3 inch increments and compact. this works best for me and is fairly quick and you have a nice level footer to work on

csl
12-30-2009, 06:15 PM
i have insalled retaining walls for 14 years, and allan block has told us to never us this method. so that is what i have based my knowledge on. i just go by their recommendations.

STRINGALATION
12-30-2009, 06:27 PM
I thought setting the base was supposed to be the hardest part its the foundation. Critical that base is.

DVS Hardscaper
12-30-2009, 08:53 PM
It is not uncommon to place a SRW (Segmental Retaining Wall) on a concrete leveling pad.

INFACT! We're building a wall right now. And on the drawings the engineer states:

6" DEEP BY 24" MINIMUM LEVELING PAD: Gravel (#57, CR6, 21A, 2B, ETC) OR 1,500 PSI UNREINFORCED CONCRETE


We will usually set some sort of grade stakes and we'll bring the aggregate base to markings on the stakes.

We do use sand to make level setting of the block go quicker. We DO NOT use 1 inch of sand as someone else had mentioned here. Thats a big no no, way too much sand which could allow for shifting / movement. We typically use about 1/4 inch of sand.


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S&S Outdoor Services
12-30-2009, 10:35 PM
I read that a 2 inch layer of 200-300 psi concrete could take the place of gravel base on Versa-Loks website. No more than 2 inches so it can stay flexible. If you're doing a concrete leveling pad of 6" x 24" than it would have to be below the frost line and would not move with the freeze thaw cycles.
I also read that it is acceptable to use up to one inch of sand to level the base but no more. If the sand is even then it should settle all the same, even it does settle just a little bit right? I'm not claiming to be the expert by any means but these are the manufacturers recommendations right on their web site.

DVS Hardscaper
12-31-2009, 10:17 AM
there's alotta stuff one can read.

sometimes experience and common sense overrides, especially when one is putting their name on the job.

Personally, I'd hate to have to tear down a 10-foot wall simply because it settled due to too much sand. That would suck financially. And it would suck from the view of a public eye. Can you imagine what the neighbors would think when they see you out there 2 years later rebuilding the wall? They'd say "don't call ABC Contractors, they had to come back and rebuild our next door neighbor's wall....."

The following is not directed to anyone in particular here: Some people here tend to get upset when I say this, but retaining walls are NOT to be taken lightly. You really must know what you're doing. Walls have more than one application - sometimes they're retaining an inground swimming pool, sometimes they're retaining a sunroom that was added onto a dwelling after the wall was built, sometimes they're retaining a driveway. So, many times once a wall is built - and once another structure is erected next to it - there is no room for failure. I'm just disclaiming this while we're on the subject. Walls can be very serious stuff.





www.outdoorfinishes.com
segmental, stone veneer, and boulder retaining wall builders
Serving MD & VA




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S&S Outdoor Services
12-31-2009, 04:20 PM
sometimes experience and common sense overrides, especially when one is putting their name on the job.


Good Point, being that I haven't been in the business long enough to know exactly what works and what doesn't I read everything I can and talk to the experts about it. I'm just trying to determine what the fastest way to lay out the base is without the chance of making the wall structurally unstable.

Fiano Landscapes
01-03-2010, 12:16 AM
get yourself i really good laser or transit. ours is self leveling and is good to 1/8" at 500'. this will cost you $1200 or so, but on one big job you make it up on labor. NEVER use sand over your base rock to get level. you will have horrible settling and if the block manufacturer or supplier sees this they wont be happy.

Not sure where this gentlemen received his information, but we install all our walls according to the srw standards from the N.C.M.A and last I checked they recomend up to an inch of sand. We always set our retaining wall material in about an inch of sand. We also use dead blow hammers to make sure the blocks are properly set in the sand. The base is always a lengthy process. I have two people other than myself that I use to set our base layers. They have been doing it so long that they set about 20'-30' an hour. It has taken a few years to get to that point, but that is why I recomend to select properly who you have lay the base. It just takes time to perfect this portion of the process.

wurkn with amish
01-03-2010, 11:53 AM
now how hard is it to set 20-30ft on an inch of sand? I will keep doing it my way on 3/4" minus and not worry about call backs. Maybe you haven't had callbacks so your just lucky...

DVS Hardscaper
01-03-2010, 04:38 PM
This "1-inch of sand" stuff is killing me :)

Pavers are set onto 1-inch of sand. Then compacted into the sand, depennding on the sand and it's moisture content, usually compacts 1/2-inch. Ta each his own. Way overkill for a retaining wall, increasing chances of a call back.

NCMA, ICPI can be good and can be bad. People built gigantic, stone, barns hundreds of years ago without some organization saying how to do it!

Hundreds of thousands of successful retaining walls have been constructed long before NCMA was ever formed! I guess since we have lawn jockeys turned construction gurus - NCMA has it's place!!!

Incase anyone is wondering how we apply the setting sand - the guys throw sand onto the footer with a roundpoint shovel, and then screed to about a quarter of an inch thich with a masonry trowell. After that, they can usually set about 100' of 75 pound blocks in 2 hours.



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zedosix
01-03-2010, 08:40 PM
For what its worth, we set our retaining blocks on a thin layer of stone dust. I would avoid using sand.

csl
01-04-2010, 10:57 AM
i have always told my guys " that if they have time to do it twice, they have time to do it right" and that is just what you 1" of sand guys are doing. you are going to end up with problems. listen to those of us who have been doing this professionally and more than just a hobby. you may go your entire life without a wall collapsing, but if one does, you are screwwed. just take the extra time and do it right, dont cheat. we replace a lot of walls every year that have collapsed or settled, and the homeowner or business always remembers who built the wall, and word travels fast, but maybe you will be out of business by the time the wall has fallen, so no worries.

DVS Hardscaper
01-04-2010, 11:25 AM
For what its worth, we set our retaining blocks on a thin layer of stone dust. I would avoid using sand.


I agree. We dont work with stone dust much, so we've gone as far where we have fabricated our own screener! We made a sturdy wood frame, and used old wire for the screen. The screener sets on top of a wheel burrow. We then screen CR8 and will use the dust for setting our base course.

Ok, so now some are wondering "why bother wasting time screening and not simply just use sand as advocated?"
The answer is because we use crusher run for the wall's base. If we use sand - it's one more ingredient we need to load and transport in an already full truck. It's more productive to have a laborer start screening gravel while the other two playas work on installing the aggregate base......





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zedosix
01-04-2010, 04:09 PM
I guess that would work just fine. I like that idea but we usually have 2 or 3 trucks on the job and stone dust is only a few minutes away. Good idea you have though.

csl
01-04-2010, 05:29 PM
thats a pretty good idea. do you have any pics of the setup?? i am lie dvs in that i have the trucks to bring extra material, i would just rather not bring an extra truck if i didnt have to. our diesel bill last year was insane.

DVS Hardscaper
01-04-2010, 05:40 PM
damn.....3 trucks on a job! I certainly hope these are Rusk-A-Roni Size jobs to justify all that metal...........

Bru75
01-04-2010, 05:41 PM
i have always told my guys " that if they have time to do it twice, they have time to do it right" and that is just what you 1" of sand guys are doing. you are going to end up with problems. listen to those of us who have been doing this professionally and more than just a hobby. you may go your entire life without a wall collapsing, but if one does, you are screwwed. just take the extra time and do it right, dont cheat. we replace a lot of walls every year that have collapsed or settled, and the homeowner or business always remembers who built the wall, and word travels fast, but maybe you will be out of business by the time the wall has fallen, so no worries.

Hey, man, do it however you want.
As I've posted before, a thin layer of concrete sand is acceptable.
Just because it's not your way does not make it "cheating".

zedosix
01-04-2010, 05:53 PM
If we only have sand then thats what we use as well. I would not send someone to pick up 1/2 yard of stone dust if I had sand on site. Our shop is located centrally and most of our jobs are within minutes of it. No sweat off my back, there is always something we need to pick up along the way anyhow.....like coffee!

stuvecorp
01-04-2010, 06:32 PM
This will sound scraper but I usually have some five gallon buckets of sand when we are doing the base.

Fiano Landscapes
01-04-2010, 06:51 PM
We have more than adequate compaction equipment. Our stone base is more than sufficiently compacted. We apply about an inch of #23 sand on the base the blocks are placed into the sand and beaten with a dead blow hammer into position. THE SAND CANT SETTLE ANYMORE THAN THAT! The only chance of settling would occur if the sub-grade or base fails. The first course of block is buried, so where is the failue going to occur. I'm not sure where this wall is going to be settling. We have done walls of all nature, and never any failures. I think this comes down to personal preferences.

zedosix
01-04-2010, 06:56 PM
We have more than adequate compaction equipment. Our stone base is more than sufficiently compacted. We apply about an inch of #23 sand on the base the blocks are placed into the sand and beaten with a dead blow hammer into position. THE SAND CANT SETTLE ANYMORE THAN THAT! The only chance of settling would occur if the sub-grade or base fails. The first course of block is buried, so where is the failue going to occur. I'm not sure where this wall is going to be settling. We have done walls of all nature, and never any failures. I think this comes down to personal preferences.

I have to agree with this especially when buring a complete block. In some cases I know of guys using sand to construct steps and simple retaining walls that have maybe an inch or two buried. I think in this case it is best to use something a bit more stable, something that water won't wash out after a rain storm. The sand does tend to find its way whereever the water flows.

DVS Hardscaper
01-04-2010, 08:43 PM
ta each his own :)

Still sounds goofy to me! But, ok :)

I envision a potential drainage issue and the front of the block getting undermined with water (which happens frequently with incorrectly built walls. And no, I'm not implying anyone here has any wall's improperly built) Then, the super dooper looper 1-inch of sand is underminded at the front of the block, thus tilting the wall forward.

I dunno....if the gravel base is near dead level, then a smidgen of sand for ease of installation purposes is plenty adequate.......



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mrusk
01-04-2010, 09:42 PM
Guys I think 80% of wall builders use sand under the first row. But 80% of walls also start to move and look unlevel after 2-3 years. Why do you think that is?

Moneypit
01-04-2010, 10:56 PM
I dunno.... I really dont think using sand would save me any time. I have done plenty of large jobs and never felt the need to use sand. I set my block directly on the crushed stone. Then again, I set my first course with a 20 lb sledge hammer. (or is it 25 lbs?)

tthomass
01-04-2010, 11:52 PM
I just excavate, compact and install about 6" of compacted stone dust. Then we just scrape along the surface as we go to level the block. Stone dust is the easiest to work with and its the cheapest. I save about $4 per ton!!

;)

S&S Outdoor Services
01-05-2010, 03:47 AM
not to sound like the idiot... but what is stone dust and what makes it better than regular sand?

zedosix
01-05-2010, 08:09 AM
I just excavate, compact and install about 6" of compacted stone dust. Then we just scrape along the surface as we go to level the block. Stone dust is the easiest to work with and its the cheapest. I save about $4 per ton!!

;)

I'm surprised to hear this from you. Stone dust breaks down and becomes an expandable slush of powder and grit once it freezes. I realize stone dust varies in regions but ours contains alot of powder which is exactly why it shouldn't be used.

DVS Hardscaper
01-05-2010, 11:48 AM
Zedo,

Based on the smiley icon TThomass used.....I believe he is being silly!

zedosix
01-05-2010, 02:55 PM
Zedo,

Based on the smiley icon TThomass used.....I believe he is being silly!

I guess I missed that part.:hammerhead: Me hitting myself with a deadblow!

STL Ponds and Waterfalls
01-05-2010, 03:23 PM
It all comes down to experience. We have a local quarry that is mixing crap(dirt) with thier 1" minus so we always have to send it back. Most installs we use 1" minus base than either use that or if we have an extra truck we'll use 1/8" minus to set the base. I used 1" setting bed of sand on some pillars and a seat wall right after I took my NCMA course. I wasn't sold on that method, but everything is still good after 2 seasons. Heck some guy's use mortar to set the first row and I would if it wasn't another materila to bring to the site.

DVS Hardscaper
01-05-2010, 04:46 PM
Guys I think 80% of wall builders use sand under the first row. But 80% of walls also start to move and look unlevel after 2-3 years. Why do you think that is?



Oh, do you mean like this wall (shown below) that was built 2 years ago (by others)??

Crash
02-11-2010, 07:17 PM
I was taught never to use sand for walls. We use limestone screenings, about an inch before compaction. You definately need to invest in a transit, it makes it a cake walk. It also just takes some time and experience to get the feel of it. We have a 45 year old that's been doin it forever, he refuses to use any kind of leveling material, he just sets them right on the hard base, beats them down with a mallet and checks the blocks with a level. He's fast and the walls don't settle so we let him do it. As long as the end product is a level wall that won't settle, you're doing your job.