Hi All,
Thanks for the read and response. I am installing a new driveway in place of the old asphalt. I Want to install it as a pair of strips 3 feet wide each. I’m building it out of cobblestones recovered from the streets of Baltimore. I’ll be putting in a crushed concrete and stone dust base and using a paver restraint system along the sides. The site has a moderate slope down to the street. The soil here is mostly clay.
So my question is do I need to excavate the area between the two strips and lay a base or is it better to leave this soil intact?
Thanks for any input.
Bruce
Replies
In general, the rule is to excavate and install base as wide from the edge of the finished paving as the base is deep. For vehicle traffic over clay soils, your base depth should be at least 12", compacted in lifts. You should dig out each strip 5' wide then. Depending on the distance between your strips, it might just be easier to dig the whole thing out, base it, and then install top soil between your finished strips.
Thanks for the reply. I'm thinkin' that I'll play it by ear once tear up the asphalt. Enjoy, Bruce
Hey epoxy breath - doesn't that cause dain bramage? - sorry couldn't resist... :-)
In general any top soil needs to be stripped, but if you have asphalt there to be removed maybe you already have a good substrate.
Interesting, I'm in California and it's common for light use driveways to have 6-8" of roadbase (3/4 crushed stone) with 1 inch of sand for laying the paver. Not sure why the difference. Frost heave issue? bad building practice?
I did one last summer -- same thing 13" of depth overall -- 8" of crushed stone (compacted as you go), 1" stone dust and then the cobble stone 4x4 for 13" = you absolutely have to have a 12" extra width on each side for stability -- each 3 foot track should be 5' wide, do not skip compacting, the necessary inches, and the width -- My job was 35 miles from Baltimore in Montgomery county -- Dudley
can anyone point me to a good reference book for this sort of thing? Something authoritative? I'm doing what I've seen other people do and I feel like I'm flying blind.
storme -- forget the books -- go here for all the help you need http://www.pavingexpert.com/Plus you just cannot go wrong with what has been stated 13 inches overall -- FHB has had articles as well as JLC that espouse this approach -- has to be 13 for vehicular traffic and 9 for foot (4 base, 1 dust and the 4 inch cobbles stone
thanks Dudly,what a great site, I actually found it awhile back and even printed out one of the pages but had forgotten about it. I've got my printer working overtime right now...The thing that I still find confusing is that it doesn't make senes to me that there would be a one-size-fits-all approach - soil type and freezing must be an issue but you never see adjustments for these. Also it doesn't help that the SOP in my area for many decorative walks is 2-3" of granite fines, the paver and nothing else, it appears to work just fine but I've yet to find any printed source that recommends the approach. Where I live I have a brick walk on just 1 inch of sand (and my soils are clay) and while it's not razor smooth, it works fine without major settling (except where it was taken up for to run a pipe under it), actually I like a little settling as the look has more character than a razor smooth walk.-s
The thing that I still find confusing is that it doesn't make senes to me that there would be a one-size-fits-all approach - soil type and freezing must be an issue but you never see adjustments for these.
Certainly no expert here. I visited a new installation of driveway pavers this afternoon. Prep was as deep as specified here. HO was extremely impressed with a 5 yr warranty. Then we got to talking soils.
I've been cutting a driveway just up the mountain from him. It's decomposed rock which packs almost to undisturbed after very little vehicle traffic. Fantastic base that sheds water extremely well. A world of difference from his new driveway with clay underneath.
My guess is that if you plan for the worst case, and it'll work anywhere.PAHS Designer/Builder- Bury it!
sure, but excavation is expensive and if it works as well to excavate less than the better job is to excavate less. I mean for foundation footings there are rules of thumb that everyone uses for simple structures but when you get into it you can also do some simple calcs that use the actual bearing capacity of different soil types. It's smart really because that way you don't have to pour an oversized footing. I keep expecting to run into the pro version of the rule of thumb for paving that says: for these loads, this kind of weather and this kind of soil, do X.And of course, just knowing the rule doesn't allow you think smart when it comes to material substitutions like using granite fines instead of road base: are they equivalent? Anyway, I appreciate the feedback. Someday I'll find a manual for building highways and my inner-engineer will sleep at night. <g>
If it helps you sleep any better, those pavers went into an excavation left from removing the previous tar and gravel driveway. I asked why it was removed. That's where the 5 yr warranty came in, along with the increased cost.
Made sense to the HO. PAHS Designer/Builder- Bury it!
There many variables that go into base depth determination that have not even been discussed yet. For instance, different paver types spread loads laterally to different degrees. A modular concrete paver with tight, consistent joint sizes, once fully compacted with a sharp, angular sand, will spread more load laterally than old street cobblestones that have relatively large gaps between them. Ultimately, base depth is determined by the worst case senario bearing capactity of the sub soil, the expected point loads, and the ability of the base and paver types to spread forces laterally. If you ride your skinny tire road bike over your lawn when it is wet, you will likely create ruts by displacing the soil. Take that same bike with 6" wide tires (I know they wouldn't fit) and you've spread the load over a wide enough soil area that it can hold you without displacement. So, if you want to really narrow down what is minimally neccessary for your situation, here's what you need to know...1. Bearing capacity of your subsoil when wet. Some subsoils lose more ability to support loads when wet.
2. Frost effects. If you live in a frost zone, the system is most vulnerable when the frost is coming out of the ground. A mixture of frozen / unfrozen base and subsoil is weaker than when it is all in the same condition.
3. Base type. An angular base such as crushed limestone will spread loads laterally better than a sifted gravel composed of mostly round shaped particles and pebbles.
4. Paver type. See above.There are other variables to consider, but their effects are negligible. In my area, I find mostly clay soils that are frost affected. I use a crushed limestone base at 10-12" depth minimum, more if the clay is extremely plastic. I also increase my base depth to 14-16" about 6' away from the paver/street and paver/garage transitions. This is especially important at the garage area. Your vehicle tires are typically loading the exact same spots all the time, and since your base cannot extend past the garage foundation, you lose some of the subsoil area your loads are being spread over.Hopefully this helps more than confuses.
no this is very helpful, just the kind of thing I'm looking for. Where'd you learn it? Are there calculations for it anywhere? Our soils are mostly clay so their bearing capacity is rated at 1000 lbs/ft^2 do you just take a 45° cone down from your pressure point to figure the bearing area of a weight like a car tire? Also, do you know if granite fines are equivalent to 3/4" roadbase in this regard? It feels like a very solid surface and I wouldn't even be surprised if it's better than roadbase actually since it's a lot of little platelets.
hey storme - you're the kind of client that if the standard is 13" we'll call for 15" just to boilerproof the project then it will be so expensive it will remain in your consciousness no masbut then again you probably drive a hybrid and we could compact your base with the three of us walking back and forth contemplating the blasphemy of our politicos and talking heads
Hi John, I have no idea where your comment is coming from, and what's politics got to do with it? Maybe you're pissed off from another thread? If so, comment there not here, eh?If you think I'm coping attitude here, I'm not. Just trying figure this instead having to learn it the hard way through mistakes and callbacks. I learned the way we all learn, watching others. I'm not arguing what I've seen is better, in fact I'm figuring out it's not sufficient. Lucky me, I got the lesson by listening rather than by having to do it twice. Dudley's turned me on to some great info and I'm asking questions to figure out what the limits are.I did my homework and saw that the recommendations were higher but I assumed it was just for freezing temp climates as most of the work I see here is NOT to the standard Dudley is asking for. What I've *seen* is 6" roadbase + 1" sand and pavers for driveways and 2-3" granite fines under both brick walkways and patios so what I'm hearing here is that a LOT of the work being done is substandard.
I used to sell Caterpillar equipment (30 yrs ago). Cat had great brochures and handbooks on issues such as road building, etc. You might contact your local Cat dealer to see whether such info is still available. However, you might find yourself up late at night reading--at least I think it's interesting learning new stuff. Cat also had tables to determine when hand-labor is more economical than machine-labor.
(IMO) In the long run, a too-strong base will bring more happiness than a few extra bucks in the pocket and a not-quite strong enough base course.
you have to differentiate between a drive way and a decorative walk -- it is like comparing the strength of a 2x8 and a 1x8 -- both are good, but used for different purposes structural and decorative. You need a base and a base had to have the ability to absorb a pretty good live load. Using fines for a walk is OK -- it is not the best or even good a corner had been cut. Everything needs a base and the stone dust is the leveler, for your job you need 8" of base compacted 3 times -- between each 3-4" lift and then the last compaction of the stone dust. Toss the stones in for the final 4" cobble stone in a pattern of your liking, fill the voids and you are done.
Want to do it a second time -- skip a step
Thanks, very helpful. I've printed out basically the entire pavingexpert site and I'll sit down with it over the weekend - it's basically a whole book. I started out with a real hack unfortunately and got pulled into independent jobs from family and friends before I was quite ready and I'm just now figuring out that a lot of the things I thought I knew how to do, weren't up to spec. Very steep learning curve for me right now. For what it's worth, once I do get it right, I don't slack on it.Adding to the noise, the local stoneyard tells everyone to use 3" of granite dust for all their paths and patios, I've always been a bit irritated by them because they don't quite seem oriented to contractors but they have the best selection around so they dominate our local market. I think what I'm starting to realize is that these guys actually don't know anything about building with stone, they're just salespeople.
Mr. Storme my heartfelt apologies
too much coffee and too much having to concern myself w/ the worst case scenarios - and I should have erased my post!
I wish my post was as giving and gracious as Dudley's ( and others )think I saw that you are in Calif - if in the southern half your supplier's re: of 3" should be more than enough for human walkways and patios ( as mentioned before there are all kinds of scenarios - is it on undisturbed ground for one )
for my area in the rainy northwest that 13" sounds extreme but if that pumptruck that Piffin ordered for that swimming pool next door inadvertently ( without permission ) used my driveway for his perch ALL will have wished we would have gone 15"sincerely john
thanks john, I appreciate the apology, and you've got my respect for making it.I'm new here and try to be respectful of the opinions I read here but I've been trying to push a bit for explanations because I really do want to build it right and I've gotten two versions. Think maybe some of that pushing came through in the wrong way.best,
-stevep.s. I live in the Bay Area - about 20 inches a rain a year, clay soils. But I think the building culture might be somewhat a problem. The drive that went in across the street while I was working on a project used 9" overall and they clearly built a lot of drives from the system they had down. That said, they did a lousy job with the design.
If you would, please post pics when the job is complete. We are looking to the same thing to our bungalow next summer - two narrow strips of pavers with grass in between.
We've got a few examples of this dating way back, but I haven't seen anyone lay it down new. I'd love to see how a new job turns out.
sounds great, but, I think you'll end up with a stone base between the two paver runs which doesn't generally bode well as a base for grass.
just a thought....
carpenter in transition
You've got a good point. Guess I'll head over to Fine Gardening and ask them what the minimum soil base is for grass.
I would love to do the same thing, it's just that our excavator keeps telling me that the stone wont hold the water and the grass will just burn.
you probably need at least 8" of soil. i'll have to ask our landscaper.
carpenter in transition