Asphalt Paving - how thick?

[Scott12v]

We're looking to pave our driveway pad with Asphalt (black top). The pad is 50x50, and fairly level. The driveway is currently 2B Limestone.

We got our first quote last night and were relatively happy with the cost ($3,700), but the quote was for only a 2" - 2.5" topcoat.

Is this normal? 2" seems pretty thin to me, but I really have no idea what it should be.

We've dealt with a lot of contractors, and we were very impressed with the guy we were dealing with. He was the only one of about 5 that we've called so far that even returned a call. He came out the same day and was very professional.

Thanks,
Scott

 

[Junkman]

2" base coat after it is rolled, and 1 1/2" top coat after it is rolled. I would also ask for the mix that they use on the highways, since it is a better quality mix.

 

[Scott12v]

This quote was definitely for a 2" topcoat only.

I just found this thread http://www.garagejournal.com/forum/showthread.php?t=8403&highlight=asphalt

and it sounds like 2" is not sufficient.

Now I'm worried about the cost to go thicker...

 

[Junkman]

My driveway was a 2" base coat for many years, until I put the top coat on. I did it that way to make sure that anything that was going to settle did settle before the top coat went on. Unfortunately for me, I had some large boulders migrate to the surface of the driveway that had to be dug out before the finish coat was put down. That is New England, where we grow rocks every winter in our driveways. The thaw / freeze cycle will bring the rocks up from 3 feet below. Every year there is a fresh crop in the lawn also, just waiting to take out the lawn mower blade.

 

[Scott12v]

Thanks for the feedback Junkman.

I'm in Pittsburgh, so the freeze/thaw cycle isn't quite that bad. I guess the best thing to do will be to wait and see what the other contractors come back with. If they all come back with a 2" topcoat, then I guess that's the standard around here.

Also, the guy said a blacktop driveway typically lasts ~ 10 years. Does that sound about right?

 

[Sundowner]

check with your town building dept./engineer.
my town demands 4" compacted gravel under 2" base and 2" top.
(but no one actually does it!)

 

[Scott12v]

Interesting...thanks for the info...we'll definitely check with them. I didn't even think about it, but I wonder if I need a permit for this.

 

[PAToyota]

Definitely best to use a stone base, base course, and finish course. I've never spec'ed a residential driveway, but you are probably looking at about 2 1/2" base course, 1 1/2" finish course, and four to six inches of compacted stone base under everything. And if you do it right it will last longer...

 

[Scott12v]

Thanks PAToyota. I just got a phone quote from another company...they use 3.25" of topcoat and his quote was the same price as the other guy...so it sounds better already. But I'm still going to look for a base coat and topcoat together.

 

[PAToyota]

The two things are that you need the stone base to provide drainage under the asphalt so that freeze/thaw doesn't become an issue and that you have both a base course and wearing course. The wearing course is finer and softer - it won't provide the "structure" of a base course.

As I say, I spec commercial stuff - which sees a lot more use, obviously. In some respects, you could likely get away with doing thinner or not doing the base course or not doing the stone base. But whether you are running your car over it twice a day or have a hundred cars going in and out of an office driveway a day, you are going to have the same freeze/thaw and settlement issues...

It is like shingles. I've heard people say you can only expect ten to twelve years out of twenty year shingles... But if you go by the book and actually pay attention to the manufacturer's requirements you can get twenty years out of them easily. Improper installation is the biggest reason they don't last.

 

[bmwpower]

The two things are that you need the stone base to provide drainage under the asphalt so that freeze/thaw doesn't become an issue and that you have both a base course and wearing course. The wearing course is finer and softer - it won't provide the "structure" of a base course.

As I say, I spec commercial stuff - which sees a lot more use, obviously. In some respects, you could likely get away with doing thinner or not doing the base course or not doing the stone base. But whether you are running your car over it twice a day or have a hundred cars going in and out of an office driveway a day, you are going to have the same freeze/thaw and settlement issues...

It is like shingles. I've heard people say you can only expect ten to twelve years out of twenty year shingles... But if you go by the book and actually pay attention to the manufacturer's requirements you can get twenty years out of them easily. Improper installation is the biggest reason they don't last.

Someone needs to write up an FAQ for this kinda stuff.

Can you provide more info on what someone should be ordering? Like types of stone, grade of asphalt, etc. So much easier to talk to stone/asphalt guys when you know the lingo.

So the stone is there to help with freeze/thaw? Didn't know that.

If you currently have a stone driveway that's doesn't have the proper stone depth, should you excavate and start over? Can you reuse some/all of the old stone?

Overkill is good!

 

[Junkman]

I would like to point out that what they say that they will put down and what they actually put down might be two different things. I would suggest that you need to know what is under the driveway now, before you start, so you know what has to be excavated to give you a good base. If you have clay on the sides of the driveway, no matter how much stone you put down, the water is still going to be trapped under the pavement. The best way to know what you are dealing with it to talk to the town engineer if there is one, or the street and road department. They will know the ground conditions in your area, and what needs to be done for a lasting job. Also, ask to see other jobs that the contractor has done, and then go out and look at them, talk to the owners, and hope for a rainy day. When it is raining, you can get a good idea of the quality of the work, because if you see puddling in the driveway, that indicates that the pavement is uneven. I go out to dinner with a friend that is in the business, and the restaurant that we go to asked him for a quote. He was a few thousand higher than the next bidder, so he didn't get the job. The new parking lot looks more like 20 swimming pools when it rains, because there are so many puddles. The contractor that did the job didn't get the right elevation to create drainage. They asked my friend if he could fix it, and he told them no, it would have to be dug out, and done over again, which will now cost more than his original quote. The price of asphalt is going up with the price of oil, so don't expect anyone to quote you now, and then expect them to do the job 60 or 90 days from now, when material prices are higher. A good contractor will give you a price for the excavation and disposal of the excavated material, and how many tons of stone it is going to take to create the base. Then they should be able to estimate the amount of material they will need for the base coat. I suggest that you have them do the base, and then come back in the fall to do the top coat. That will give the base time to settle and firm up. I drove on base for about 10 years before putting the top coat on.

 

[PAToyota]

Someone needs to write up an FAQ for this kinda stuff.

Can you provide more info on what someone should be ordering? Like types of stone, grade of asphalt, etc. So much easier to talk to stone/asphalt guys when you know the lingo.

First problem with an all enclusive FAQ would be size... The specifications booklet for a project starts at about an inch thick and goes up from there...

The next problem is that designations are most often based on the state highway department specifications. You can use the AASHTO designations, but the yard will look at you funny... What we spec is known around here as "2B modified" - the "2B" is AASHTO #57 (certain sizes of stone) and the "modified" means that it adds smaller "fines" to the mix that enable it to be compacted. Straight 2B (or #57) doesn't have the fines and is like marbles - no way to really compact it. There was a discussion on stone a few months ago and there were half a dozen designations listed for AASHTO #57 based on where the poster was living.

We start off with MasterFormat for the specifications - all the variations and standards and regulations and everything else. But even from there you really have to know what you are doing - when to use what paragraph or what clause or such. Specifications can be a whole specialty within the architecture field. I'm working on getting my certifications on top of my architectural registration. You can find out some more here - http://www.csinet.org/s_csi/index.asp - if you're really interested...

So the stone is there to help with freeze/thaw? Didn't know that.

If you currently have a stone driveway that's doesn't have the proper stone depth, should you excavate and start over? Can you reuse some/all of the old stone?

Yep, the stone is for drainage out from under the asphalt.

If you want the best possible finished product I'd say remove everything and do it right. The problem with reusing stone is that by the time you scrape the asphalt off the top and run around in the existing stone with a loader you've likely mixed it in with the soil or pushed the soil up into the stone.

If you really want to do it right, you first lay down a geotextile fabric, then the stone base... That keeps the stone out of the soil...

 

[bmwpower]

Thanks guys. I'll start poking around. Sound like I'll have to start over...did I mention my driveway is like 300 foot long?? Ugh.

More questions:
Do they make an industrial type of "sifter" to remove the dirt from stone? Would be a shame to chuck all that stone.

So the base is only one type of stone in your area? I guess I will have to call around.

And where can I get the geotextile fabric? I assume Home Depot doesn't have this kind of thing.

What makes the base coat different from the top coat of asphalt? Are they of a different grade?

 

[PAToyota]

More questions:
Do they make an industrial type of "sifter" to remove the dirt from stone? Would be a shame to chuck all that stone.

Back when I was a kid, my father built a frame about 3' square out of 2x6s with legs and hardware cloth with about a 1/2" opening to it to sift rocks out of our garden. You could likely build something similar, but for the size you are talking it would take forever. I've seen buckets for loaders that "sift" rock, but haven't used anything like that so couldn't really advise...

So the base is only one type of stone in your area? I guess I will have to call around.

Most of what we spec is 2B modified for stone base. There are others. Basically you do want a "modified" stone with the fines so that you can compact it.

And where can I get the geotextile fabric? I assume Home Depot doesn't have this kind of thing.

I picked up a roll at a builders' supply.

What makes the base coat different from the top coat of asphalt? Are they of a different grade?

The base course is coarser whereas the wearing course is finer and has more asphalt to it. You've likely seen the difference without knowing it. Some places they don't use the wearing course on the shoulders of a road and it isn't nearly as smooth and looks like it has larger "chunks" making it up... Tried to find some images to link to, but couldn't find anything side by side...

 

[bmwpower]

This geotextile fabric...is it the same as landscaping fabric?

 

[PAToyota]

Pretty much so. There are different kinds. I think the geotextile fabric is less permeable, though...

 

[CJseven]

We're looking to pave our driveway pad with Asphalt (black top). The pad is 50x50, and fairly level. The driveway is currently 2B Limestone.

We got our first quote last night and were relatively happy with the cost ($3,700), but the quote was for only a 2" - 2.5" topcoat.

Is this normal? 2" seems pretty thin to me, but I really have no idea what it should be.

We've dealt with a lot of contractors, and we were very impressed with the guy we were dealing with. He was the only one of about 5 that we've called so far that even returned a call. He came out the same day and was very professional.

Thanks,
Scott

Wow, That price is for a 50X50? I don't fell to bad then I had our drive done last summer by a large contractor that does all the highway jobs in this part of the state, they were doing the gravel road in front of my house so I had them do the drive when they came by. I have 4" compacted the drive is 10'X400' and cost me 3900.00. It has held up real nice so far, I've seen a few jobs that some of the local small contractors have done and they are really horrible looking.

 

[mpraddict]

Around here, I spec an aggregate base of 8" #2s with 4" #304s over, then a 2 1/2" base ashpalt layer and 1 1/2" wearing course. But like PAToyota, I only do commercial work. This spec would be for a standard duty pavement (not subject to heavy truck/delivery loads). Of course this is subject to the soils condition of the site (in commercial work we would have a geotechnical report giving soil and paving recommendations).