Proper base layer for interlocking stone
I’m planning an interlocking stone driveway and the stone vendor’s literature wants the pavers installed on a compacted “crushed stone base” covered with a 1″ bedding layer of sand. So- what exactly do they mean by “crushed stone”?!
It’s a basic 1-wide driveway in Toronto. The plan is to excavate for a 6″ base on a layer of landscape fabric. Subsoil is clay till. Should I use limestone screenings for the base? Crusher run? Or clear stone (ie. concrete aggregate)? The latter will drain better but won’t compact much. The former will compact fine, but won’t drain as well and the worry would be frost heaving. Crusher run’s a balance (basically dust to 3/4″), giving a balance of both.
The paving stone folks are not much help- they know how to make the stones and aren’t much help with advice on how to lay them.
Replies
I would be looking for '5/8" minus' meaning crushed rock that's screened with a 5/8" screen and has a lot of small stuff and fines in it. It will compact extremely well. My driveway is 5/8" minus and after a few years it's like concrete where the wheels hit it.
Who is the manufacturer of the pavers?
I'm doing a paver patio at my house right now using Unilock Brussels Block. The local dealer told me to go with 5" of crusher run gravel as the base and 1" of crushed limestone as the bedding material. Their thinking is tha the crushed limestone is more stable than sand and less likely to shift. We'll see if he's right.
Definately crushed limestone in liew of sand. Sand is old school and for good reason, it doesn't compact nearly as well, nor it it nearly as stable.
I might add that you should compact it in layers of about 2" to make sure the bottom stones are well packed. Spread 2" of 5/8 screened, compact it, another layer of 5/8 screened, compact it, all the way to the 1" layer of crushed limestone. --------------------------------------------------------
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The mfg is a local company called Brooklin.
Great, this is exactly what I needed. So I'll be getting "3/4" crusher run" material (3/4" minus, from dust to 3/4") because that's the stuff locally available. Compacting it in 2" lifts, topping with 1" of limestone screenings (ie. crushed limestone) as a bedding layer. The bedding layer is dumped and screeded flat but not compacted until the stones are in place, ie so you can embed the stones into the bedding layer by running the compactor over them.
Have I got it right?
Thanks again, guys- this place is an awesome resource!
sounds about right, only thing is, .. you should go with at least 1 foot for a laneway, 6" is okay for a walkway. You can compact after 4-6 inches, putting a sprinkler on it, wet it down will make it compact even better. I like to use chain link fence rails to screed over to establish the grade, their straight, app 12 ft long and easy to work with. Resist the temptation to grade it with the last (we call it stone dust, or pea gravel) layer, it will settle over time and where you spread it thick, it will settle more and you'll wind up with puddles (yes it will drain through the pavers, but you'll get ice in the winter). When compacting keep the vibrator moving, go north-south then east west, when you shut it down, turn if off and keep going till it stops.
I didn't comment before on the depth because I wasn't sure, having only done patios. But 12" does sound more appropriate for a driveway.
As for the top layer, the limestone screenings, you want to compact that layer also. Everything should be compacted.
Pavers too. As you set the pavers give them a few raps with a dead-blow mallet. --------------------------------------------------------
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we compact our base layer of 3/4 crush (gravel with the dust, helps bind everything together) every 4-6 inches, wetting it down stops all the dust and I think, helps the rocks slide and fit tighter, then screed the stone dust (don't like sand, too many things will grow in it, as opposed to stone dust). The stone dust is not compacted. After the pavers are laid run the compactor over them as directed. This will compact the stone dust, level out the pavers, and lock them together by forcing excess stone dust up into the joints. Once this is done then you can sweep more dust into the cracks and vibrate or water it down.
You have more experience in this fied that I do, having done just a few patios and no driveways at all. The patios I've done are holding up well, including my first one about 8 years ago. But I for one will do it as you describe from here on. This thread is showing me just how much I don't know.
MoltenMetal, don't listen to me. Listen to these other guys. :)--------------------------------------------------------
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Sounds right except you need to do more than 6" of base material for a driveway. I wouldn't do anything less than 12".
I attached a copy of the Unilock Tech Guide which will vary from your manufacturer somewhat but it has other good information that applies to all interlocking paver installations.
A couple of other suggestions:
Drainage is also going to be key since you are concerned about the soil. Route any nearby downspouts away from the driveway even if that means tieing them into draintile. Depending on the topography, a perforated draintile with filter sock may be in order along one or both sides of the driveway as well.
While you have everything torn up, it would be a good idea to run a couple of empty 1 1/2" PVC conduits across the driveway to accomodate future landscape lighting or other uses. It's cheap and easy now compared to a complete PITA if you need it later. Pull strings in the conduit would make life even easier down the road.
Some of these replies are getting close. I've been doing this for a living for over 20 years not too far from you, around Buffalo.
Geotextile in the bottom of the hole is a good practice, especially with clay subsoil. A foot of base for sure on a driveway, but don't use a foot of 5/8 or 3/4. Start with 2 inch crusher, or even 2" recycled concrete.
When you get 8-10 inches in, switch to 1" or 3/4". We use 1/2 inch galv. pipe for screed guides. Screed the 1", tamp one more time, then use the same pipe for screeding the sand.
Depending on how big your tamper is, 2-3" lifts are better than thicker ones. If you plan to use polymeric sand for the joints, read the label. Some say not to use limestone screenings as a setting bed.
Good luck with the project!
Bear
Hey, who stocks polymeric sand around the Queen City?
I'm more or less new to the area and haven't found all the real construction stores yet, just the big boxes.....
Thanks!
You can get poly sand from Unilock on Smith St. in Buf., Reboy supply in Elma, Scranton's Thruway Builders on Walden, and probably other places. I've never seen any at the boxes.Bear
much obliged!
I can do 1' depth of sub-base on the front part of the driveway where the car will normally be parked, but the last 1/2 closest to the garage can't go that deep without risk of killing a huge walnut tree. 6" is all I'll be able to do there. Fortunately the garage is really my shop (ie. no cars in there unless they're being fixed) so car traffic on that part is only occasional.
The deeper I go with the excavation, the deeper a pan to collect water I'll be making, and a good part of that will end up in my foundation drainage tile. The native subsoil is a dense clay till that doesn't drain very well at all, and the site's more or less flat- options for drainage are limited. I'll slope the base of the excavation away from the house and try to grade the pavers a bit in the same direction, but that's about all I can manage.
We'll run the one downspout completely under the drive (in clay drainage tile? Big O's a little to flimsy only ~1' under a driveway I think). Fortunately that'll be in the 1' sub-base portion. Can't hurt to run a little conduit too- good suggestion!
We'll try to screed the top of the base layer to give us the slope and flatness we want. I hear you about trying to forgive too many sins with the bedding layer!
We'll go with limestone screenings (stone dust) for the 1" bedding layer but not compact it until the stones are laid. That makes the most sense to me. If you compact it first it is no longer a bedding layer.
Thanks again for all your help, folks- this forum is awesome and my addition project is proof of that!