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View Full Version : Looking for SRW building help (NOT pricing)


MDLawn
04-13-2010, 10:33 AM
Seasoned Hardscapers,

I have a friend who needs some work done with some involving a small wall (around 2ft.) to be built. This backyard area is roughly 20' x 15' and gradually elevates up 12-14 inches to the neighbors back yard which is higher. This was an old garden from a previous owner that they would like to take back and make more lawn/living space with. I suggested the wall so as to eliminate a highly sloped backyard. I have done the Allan Block Retaining Wall course and will be using their Jumbo Junior stone. Please this is no time to argue about what block is best, it is what is readily available. I want this wall to last for them, so based on the knowledge obtained from the AB course would you advise on using drainage for this short wall? They also would like this wall to hold up a planting area to create a screen from the neighbors. Would a plant such as an arborvitae be a bad or good choice in terms of the wall holding up (roots, etc...). Also I have heard people using what we around here call "Crusher Run" for the base and #57 stone for the drainage stone behind the wall and also even for the base. I have even seen a 6" crusher base with 6" #57 base, which may be overkill for this small project. Any input on what you have found works best is appreciated. I have also seen mixed feelings on using a geotextile under the base and behind the drainage rock to prevent fines from working into the drainage stone. Again any input. I just want this to turn out great, as long as they want to do it. If you can help out with any information great! If you need more site info just let me know.

Thanks in advance for any help.

PatriotLandscape
04-13-2010, 09:06 PM
1. NCMA Spec 12 inches of 3/4 clean stone behind all walls. you can use 6 inches if it is a core fill wall but I reccomend you stick with 12.

2. for the base you can use crusher run or clean 3/4 the clean stone is easier for compaction and minor leveling

3. use corrugated pipe daylighted every fifty feet out the face of the wall to remove incidental water

4. plant the arbs 3' from the wall. any closer and it may influence the wall in a way they dont want.

5. NCMA currently does not spec fabric in srw walls. but a manufacturer might recomend it.

MDLawn
04-13-2010, 10:38 PM
Thanks. I may have to rethink this. Their yard is tiny enough and I'm not sure they want to lose the space for the wall and arbs. I may just make a berm to plant the arbs on, edge it, mulch it instead of the wall. But I'll still think about the wall. Thanks for the info

xtreem3d
04-15-2010, 09:00 PM
1. NCMA Spec 12 inches of 3/4 clean stone behind all walls. you can use 6 inches if it is a core fill wall but I reccomend you stick with 12.

2. for the base you can use crusher run or clean 3/4 the clean stone is easier for compaction and minor leveling

3. use corrugated pipe daylighted every fifty feet out the face of the wall to remove incidental water

4. plant the arbs 3' from the wall. any closer and it may influence the wall in a way they dont want.

5. NCMA currently does not spec fabric in srw walls. but a manufacturer might recomend it.

Are you saying it's o.k. to use 3/4 clean as a base? (item #2)

CertPro
04-16-2010, 07:38 AM
Are you saying it's o.k. to use 3/4 clean as a base? (item #2)

Absolutely!

xtreem3d
04-16-2010, 07:50 AM
correct me if i'm wrong but material of the same size doesn't compact well ? thats why you would use 1" clean behind the wall ....because it can't compact and allows for drainage...am i missing something?
steve

MDLawn
04-16-2010, 11:08 AM
At the SRW course I attended for Allan Block they are using that kind of stone for base and backfilling. I cannot remember what the instructor said the reason was. But I guess thats the way it is now.

xtreem3d
04-16-2010, 06:35 PM
if that is so....why do road crews use 3/4 minus for compacting base for roads? i am no expert but i wouldn't think of using a "clean" material to compact for a base,
steve

MDLawn
04-16-2010, 09:15 PM
I was at the training to start learning about building walls but there were a lot of guys there who already do this sort of stuff. They were also confused about the use of this type of stone. However, the instructor ensured this was the correct way. And the videos from Allan Block show them using this stone and not a road base or crusher run stone. Still trying to figure this out as to what to use with these projects.

DVS Hardscaper
04-16-2010, 11:22 PM
yes, you use fabric behind the wall. Even if you are using grid. Your wall engineer (for the walls 4' and taller) will specify how the fabric should be placed.

yes, 3/4" aggregate can be used for the base. it self compacts because it is angular in composition.

It (3//4") is used for backfilling because it allows water to pass thru, not necessarly because of compaction. Think of the gum balls in a gum ball machine, and imagine pouring water over the gum balls. Water always follows the path of least resistance, and that is the name of the game when it comes to SRWs. Although, the SRW's drainage chimney is intended as a LAST RESORT drain system, an all else fails system. The mindset is to find other ways to route/get the water away from the SRW.

A SRW base can be CR8 (crusher run), 3/4" gravel, or flowable fill concrete.

Also, our drainage chimneys are usually 18-24" wide. Seldom do we do one at 12". The wider - the better.

yeah, we've built a wall or two........or 3, or 4......



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xtreem3d
04-17-2010, 01:13 AM
are you saying that if you compact 3/4 clean and 3/4 minus both with adequate moisture content , that they will both compact to the same "hardness"? i respectfully just don't see it. i am going to try both later today just as a comparison

MDLawn
04-17-2010, 09:54 PM
yes, you use fabric behind the wall. Even if you are using grid. Your wall engineer (for the walls 4' and taller) will specify how the fabric should be placed.

yes, 3/4" aggregate can be used for the base. it self compacts because it is angular in composition.

It (3//4") is used for backfilling because it allows water to pass thru, not necessarly because of compaction. Think of the gum balls in a gum ball machine, and imagine pouring water over the gum balls. Water always follows the path of least resistance, and that is the name of the game when it comes to SRWs. Although, the SRW's drainage chimney is intended as a LAST RESORT drain system, an all else fails system. The mindset is to find other ways to route/get the water away from the SRW.

A SRW base can be CR8 (crusher run), 3/4" gravel, or flowable fill concrete.

Also, our drainage chimneys are usually 18-24" wide. Seldom do we do one at 12". The wider - the better.

yeah, we've built a wall or two........or 3, or 4......



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Thanks, just the reply I was looking for. This wall I may do, however, would only be 3 courses high with the first buried a bit and may 20 ft long. Do you think that what you described is totally necessary? As the other poster suggested to having any large plants at least 3 feet back is that 3 feet from the back of the drainage stone or the wall? I think this would just lose too much space for the and I am hoping a berm with the arbs would give them what they need although the wall would look soooo much better.Try to avoid a fence as there is already the neighbors chain link fence.

DVS Hardscaper
04-17-2010, 10:01 PM
I'm not sure what block you're using, so Ii dont know what your 3 courses measures. Most block is 8" ht. so I'll assume you're wall is 2'?

If so, it's not that dramatic, you could most likely plop the plants where ever you want.

MDLawn
04-17-2010, 10:13 PM
I'm not sure what block you're using, so Ii dont know what your 3 courses measures. Most block is 8" ht. so I'll assume you're wall is 2'?

If so, it's not that dramatic, you could most likely plop the plants where ever you want.


Sorry, my thought was to use Allan Blocks Jumbo Junior since it is readily avaiable. So yes I think 3 courses is just shy of 2 feet. I just worried that over time the roots may push to hard against the wall but being a short wall they may just go down into the ground. Would you still use drainage pipe behind a wall this short? Or just the stone? Thanks for answering my questions.

DVS Hardscaper
04-18-2010, 12:11 PM
I'm not root expert. If it's shrubbery, (arbs, holly, photonia, lilac, etc) I'd assume the roots would not harm the wall. Now a Silver Maple - yes.

I would still use drainage pipe and I would use some clean 3/4 aggregate behind the wall so that any water could still find it's way to the pipe if need be. But remember - the name of the game is to find a way to route water away from the wall. that drainage pipe is not supposed to be the primary drain. About 7 years ago we built a small wall, about 2' in ht, 15' long - no gravel, and 6 months later we had to rebuild it. Lesson learned.



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