What Grade of Base Should I Use?

[Marbury]

I have excavated approximately 8" of topsoil for a paver service walk I am laying in my backyard, and now I need to order the base material. The landscape supplier I spoke with has recommended Grade 8 crushed stone gravel. Is this the proper material?

As always, thanks for the advice!

Tim

[Rick Bischoff]

as long as it is compactable crushed stone from 0''-3/4'' it should be a fine base for pavers.

around here its called 21-A CR-6 or Crusher Run

4''-6'' is the general depth under patio's and walkways, 1'' of course sand will also be screeded on top of the base

[Stonehenge]

AASHTO recommends 4-6" of crushed stone for flexible pedestrian pavements, we usually do 6-7" (more on occasion - stone is cheap insurance).

But we don't use bedding sand at all. There are two sides to the sand arguement, and this is the side I'm on.

[Bill Schwab]

We used CA-6, or grade 8 when we worked in the Illinois. Basically, a one inch chip, 3/4 inch chip 1/2" chip, 1/4 inch chip all the way down to fines. I wish they would create one gradiation name for base in every state and stick to it.

[HardDaysKnight]

Originally posted by Stonehenge
AASHTO recommends 4-6" of crushed stone for flexible pedestrian pavements, we usually do 6-7" (more on occasion - stone is cheap insurance).

But we don't use bedding sand at all. There are two sides to the sand arguement, and this is the side I'm on.
Jeff,
How do you get the base to the point to lay your paver's easily
without the sand? I can see how it could be better. Less chance
of shifting or dipping, but It seems harder to work with than
having some sand. I would do much more of this work if the
sand was eliminated. Now I'm curious about this as well as
the 2 sides to the argument. Maybe it's another thread altogether.

I also like the 6-7" for insurance. For the price of the product
why not have that security?

[Rick Bischoff]

Originally posted by Bill Schwab
We used CA-6, or grade 8 when we worked in the Illinois. Basically, a one inch chip, 3/4 inch chip 1/2" chip, 1/4 inch chip all the way down to fines. I wish they would create one gradiation name for base in every state and stick to it.

I agree about using only one name. It makes it somewhat confusing when there is thirty names for the same material.

[Pelican]

In my part of NY, we call the same material "Item 4".

I wasn't aware of the sand/no sand theories, can someone explain "no sand" to me? It seems like no sand would nearly eliminate ant activity after the job is completed.

[Marbury]

Originally posted by Rick Bischoff
as long as it is compactable crushed stone from 0''-3/4'' it should be a fine base for pavers.

around here its called 21-A CR-6 or Crusher Run

4''-6'' is the general depth under patio's and walkways, 1'' of course sand will also be screeded on top of the base

Thanks for the response. It sounds like I am using the right material.

Assuming I use 6" of base, should I compact after laying several inches, and then compact again when the base is all down? Or should I just compact when the entire base is in?

[NCSULandscaper]

its best to compact in increments.........i usually compact every 2" of base material just to get even compaction and no soft spots which will cause settling and uneven paver surface.

[PSUscaper]

"I also like the 6-7" for insurance. For the price of the product
why not have that security?"

I use to say this quite a bit.......but, no I'm not so sure. Sure, stone is pretty cheap, but do you really understand the cost of doing 6-7" compared to 4"?????

Cost of stone is relative.....maybe???? but with the price of fuel, you really can't just say stone is all that cheap anymore. It may be costing more to truck the stone than it is to buy it.

Then there's the cost of installing......4" can be compacted pretty much in one layer.....6-7" involves applying two layers, compacting twice, raking twice, etc. etc. etc.....

Then's there's the big killer that adds up....excavation. Making it 6-7" doulbes the amount of dirt needed to be removed. I don't know, but dirt isn't not cheap to remove off of a property for me.
Also, how bout those hand dig jobs???? Isn't it a lot harder to hand dig, and even worst, hand remove all that extra dirt?

I'm the last to talk about base depth. I think I've done walks with 20" bases before (not for the reason of strength, but for the reason of having to much fun with the excavator). But, this year, I have really started looking back and realize that installing all that extra base costs me a lot freakin money!

I know its insurance, but as I look back, I have to say, I can't necessarily say one job that has a thick base looks better than a job where the base is less.

So, what I want to know is should I be much tighter on my base laying???? I think so, but just want to see what others say. I guess it is more relevant on larger jobs where a extra inch means a extra 200 tandems of dirt removed and another 200 of stone brought in, but I would like to know how tight guys get with small jobs......are you trying to be exact??? Do you just start digging and guess?? Are you aware of the costs associated with adding more base????

[HardDaysKnight]

Penn, Why would adding more base, removing more soil etc. ever
cost you more money. It should be figured in the mats and labor cost prior to bidding and you would make more money for doing so.
It wont make a job look better, Just more structurally integral.
I think it's an interesting option , not a necessity though.

[Marbury]

A couple more questions for the pros:

1. Does the bottom of my excavated area need to be COMPLETELY flat and level before I add the crushed-stone base?

The walkway I am laying is roughly 4x18. I have excavated roughly 8"-9" of soil (by hand!), and I know for a fact that the bottom of the "trench" is not completely flat and level. Do I need to screed it somehow, or will the stone base fill in any low areas? I'll probably have an average of 6" of base material.

2. Related to the first question, should I compact the soil surface before I start adding stone? The soil is pretty heavily clay-based, so it's pretty hard already.

[AZTLANLC]

1. Does the bottom of my excavated area need to be COMPLETELY flat and level before I add the crushed-stone base?

It has to be as close as possible to the final grading of the pavers, if you over excavate don't put soil back.


2. Related to the first question, should I compact the soil surface before I start adding stone? The soil is pretty heavily clay-based, so it's pretty hard already.

Yes but if you are using a plate compactor it's going too be a little harder, so maybe spread a real thin layer of base, that way the compactor will run smoother,

About the clay which makes things worse. Make sure that you have at least 6" of base and would be a good idea to use Geo-textile to separate the aggregate.

8 - 9" excavated?
Just make sure to account for the sand, and the thickness of the pavers.

Also don't forget proper moisture to ensure good compaction

[LerchBros]

A national name for base aggregates would be great, i agree!! We have CR-6 here. For a pedestrian walk we use 4-6" of base compacted on 2-3" lifts. ICPI says to do it this way and we try to keep it by the book. Our patios and walked are priced according to the specs, some customers want to save a little dough by using less base, they also loose a lifetime settling guarantee. Watch your excavations, over digging costs a lot more in material and headaches, a lazer level can fix all that.

- To answer the question about the level sub-base, no the soil does not have to perfect, but it should be compacted with a plate tamper. After compaction the area should be ready to go. As long as your base aggregate is consistent there shouldn't be any problems, all of the tweaking and leveling can be done during the lifts. Hope this helps