CR6, CR8, GAB.....What to use and how much?

votumamorNovember 16, 2008

Hello all from Clarksburg, MD!

I badly need more parking space and have excavated two separate spots. Each about 20'x20'. So far I've excavated 4-5" by hand (and find myself looking at Bobcat prices) and framed them with 4x4. I plan on filling with almost all base material and compacting a lot with a jumping jack tamper I found on good ole Craigslist...then topping off with a thin layer of 3/4" gravel I already have.

Is 4 inches of base material enough?

Whats the worst that could happen if its not?

Which base material should I use?

I've been quoted:

CR6 at $16 / ton

CR8 at $40 / cubic yard

GAB at $17.50 / ton

Are all these materials similar?...gravel with dust mixed in? I need to knock this project off yesterday, any input is greatly appreciated.

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"Which base material should I use? "

Use the CR6. When delivered this select base material should be composed of mostly uniform crushed rock around 3/4 inch size along with fines; a grit and rock powder sufficient to fill the voids between the larger aggregate.

"Is 4 inches of base material enough? "

The answer is probably not, but that depends on a lot of other factors; type of subsoil under the base, expected moisture levels in the subsoil, freeze depth in winter, and weight of the vehicles using the pad. Even 8 inches of base won't work well where the subsoil becomes saturated during wet periods.

"Whats the worst that could happen if its not? "

Expect pot holes to develop. The select base material will begin to intermix with the subsoil and lose it's strength. The surface will become uneven and the gravel top coat will intermix with the base and shift to expose the base in areas. Under freeze/ thaw conditions the pad may fail and become a mud pit.

    Bookmark   November 17, 2008 at 8:43AM
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pls8xx, thanks for informative reply. I'm dying to get this project over with, but not much point if it ends up unsuccessful or I have to constantly make repairs.

Not sure how to judge the subsoil. On the surface I have no problems with water building up or an excessively soft ground during wet periods. Its on a slight and even slope.

Is there enough information here for you to take a best guess on how many inches of compacted CR6 base I should use?

    Bookmark   November 20, 2008 at 2:39AM
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No, I'm sorry, there is not enough information. The factors involved are complex and interrelated which is common for landscaping or civil projects. In my opinion, the best way to assess the situation is through the traditional use of a plan drawing where the collected data are brought together and can be viewed in whole. While it is not beyond the ability of a homeowner to complete a base map, my experience at this forum has been that few care to take the time and trouble to go that route, preferring to just do something and take the chance that the result will be good.

    Bookmark   November 21, 2008 at 9:25AM
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