Excavation depth for pavers, have lots of sand below topsoil
Hi,
I'm installing pavers, and I just dug down and removed 7 inches of topsoil and sod from the 260 square foot area where I plan to lay my patio. This morning I had a guy with a dump truck come and take out about 5 or 6 cubic yards of topsoil from my driveway.
The dump truck guy from the excavating company recommended that I go deeper and remove all of the topsoil down to the clay or hard bed, and call him back for a second load because he said the topsoil that is left will eventually decompose and my pavers would sink after a few years. Bummed, I just paid him 250 bucks to remove the dirt from driveway. The reason why I only went down 7 inches, 4 for gravel, one for sand and two inches for pavers, which is what I am reading is acceptable for pavers.
Anyway, after he left, I dug a couple of small, deep holes to see how much topsoil I have left, and I went down about a foot more, there is maybe an inch or so of topsoil left max, but below that, it's all sand in one area. As far as I could go – more than a foot deep, it looks like maybe playground sand. Does all this sand have to be removed too - down to hard clay?
In another area of the patio, I dug down a foot and there seems to be a mixture of sand and clay. Do I have a problem? Lot’s more digging to do?
If I just remove the inch more or so of topsoil will I be OK with the sand in one area and the sand – clay mixture in another area?
What should I do? Can I just remove the one inch of soil left and call it a day and start laying gravel base?
Joey,
Stick with your original game plan, but be sure to use a vibratory plate compactor to set the crushed rock base. If you are really concerned, you could also use a jumping jack compactor on the earth before throwing in the crushed rock base. I think the dump truck driver just wants another $250.
I am going to go out on a limb here and disagree with kinnanscaping and Fine Edge but not because they are really wrong. As a general rule what you excavated is the recommended depth for a patio but (here comes the but) I will always dig until I reach undisturbed subsoil. If the sand is natural to the area and thus the subsoil, then this will be fine but if it is left over from construction of the home I would remove it. This is probably overkill but it is also why I guarantee my work for 5 years.
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What is your climate like, do you get deep frost during winter months? I think you will be fine, I would just level the base as best you can, compact it just go over it once or twice. Lay out your geo textile then proceed as you would. Don't lose sleep over it. Your patio will be fine.
Just don't tell me you are in Alaska or anything, if so void my comment!
well, we are finishing up a patio/walkway/retaining wall job now, and an area in the patio next to the steps of the house had gummy clay backfill, which resulted in an overdig of 3' to remove bad area and compact.........if you want it to last, find a good sub base. If its not possible, make sure you wrap your base with a woven geotextile fabric to help support your base material from going into the sand
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Matt Thompson
Thompson's Landscaping
Henderson, NC
The only thing I would add upon what everyone else said is to maybe just dig out the extra loose soil if you are that concerned about, if it were me I would. Maybe put in 6" of crush and tamp it in 2" lifts. And possibly tamp the pavers in poly sand once it's laid.
Man, I wish I only had to excavate 7" for my patios. Just got done with the dig out for my next patio today, dug out 12". 8" for crush (tamped every 8") 1-2" for dust and 2 1/2" for my pavers. With the Central New York winters and the way the ground freezes around here I take extra precautions.
Thanks so much all for your helpful advice. In answer to above question, I live in South East Michigan climate. We get frost here but not the kind they get in Alaska.
Just a couple of questions in regards to the above technical terms you experts use, by crush I assume Spruce Ridge means some kind of crushed gravel, is this correct? If so what kind? Also what is meant by “lifts?” Sand?
Also what does NCSU mean by “Sub base?”
Is geo textile laid down on the soil prior to laying my gravel?
Yes, Crush is referred to as class 5 (3/4" minus). A lift, is layer of uncompacted "crush" or whatever base material you are using about 2-3 inches thick (depends on your plate compactor). Yes, some kind of geo textile should be laid down prior to basing for your patio. We always excavate down 9", 6 for the base and 3 for pavers and sand. Mite also want to consider using water before compacting in a mist. This helps get a rock solid base.
Thanks so much starsandstripes and all, this is a wonderful forum, a great resource.
What kind of geo Textile would you experts recommend for my area?
I live in South East Michigan, a USDA 5b hardiness zone, if that means anything to you, and the soil I am installing pavers on is in one area sand and in another area a mixture of sand and clay (this is after excavating 7 inches down).
We get below zero here sometimes but I’m not sure if you would consider that a “deep frost climate” that eastern1 refers to…
Frankly I would love to pay someone to do this, but I am now laid off and money is really tight with the family lately, so I am going to have to do this myself, we bought the pavers in on sale in April at Lowes, and finally were able to come up with the cash to buy the gravel and sand. We got the Oldcastle Harvard pavers, they are two inches thick by 8” long, about 9 per square foot.
A guy at Lowes recommended that I buy Flagstone gravel for my base, would this be a good choice?
Your base should be 3/4 minus crushed stone. To save money and your back, contact a local stone yard and have a truck deliver bulk material. Do not buy your base in bags due to cost.
Quick question, the guy at our local building supply place said to use what he calls his 21A, which he says is similar to the 3/4 minus crushed stone and calls it his 1 minus. His is limestone and he says the largest chunks are one inch and it goes down to fines, or dust. Would using this instead of the 3/4 minus as a base be OK?
He also has slag sand and says to use that as my sand base on top of the 1 minus. This sound OK to use?
as long there is not organics on it you can use it, I would not use the slag sand tough, look for approved concrete sand, that in my area is hard to find so we use 3/8 or 1/4" instead
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I was thinking about buying a diamond tipped blade for my circular saw to cut pavers. Does anyone have a recommendation on what kind of jig to build to hold the pavers stable while cutting?
I was just thinking of screwing two strips of wood parallel to each other to a plywood base and slide the paver between the strips but eventually the strips will get all cut up - is there a better way? Or are the strips sacrificial and I will have to replace them regularly?
