New concrete driveway question

[Keith Boeheim]

Our home in western new york is 4 years old and the driveway is gravel. There are 10+ other homes on the street built about the same time as ours and had gravel driveways. A concrete flatwork contractor put in about 5 driveways last summer and did minimal excavation. He told the home owners that by them driving on the gravel for 3-4 years was the best subbase there could be and if he didn't have to excavate much it would also cost them less. The problem I see is that the driveway is above grade and even bringing in topsoil it would take a lot to feather it out so the lawn looks flat. Any opinions on this contractor's statements or could he have excavated so that the driveway was flat with the adjacent lawn?

I'm thinking of putting in a driveway in the spring. Thanks for any replies.

kb

[Colbyt]

I am not a concrete contractor. IMO he told you mostly the truth. Sub base and drainage are both important. This doesn't seem to reconcile with the finished product you want.

Without seeing your lawn I can't address the drainage issue. You can always dig out X tons of dirt and gravel and replace it X-y inches of gravel to establish the same base at a level grade.

Colbyt

[Lyle B. Harwood]

? Any opinions on this contractor's statements or could he have ? excavated so that the driveway was flat with the adjacent lawn?

I would say it depends how accurate your statements are.

Base is everything in flatwork, but gravel isn't a good base for a driveway- the right base is crushed rock.

It needs to be compacted, and I'm not sure that the hit & miss process of driving on it would compact it sufficiently. The other issues are how deep it is, and what's under it.

Personally, unless your driveway is crushed rock, I would advise excavating it, and replacing it with a properly designed and executed base.

Best of luck, and let us know how it comes out!

[default]

He could have, it just would have cost more. If you're willing to PAY more you can have it done the other way.

--Goedjn

[raven]

Frankly, I think it's far easier to raise things up a bit than it is to move everything around. I'd let him put in the driveway and get a dumpload of crushed stone to put along the edges. The grass will eventually grow up through the stones and you'll have a sturdy edge to the driveway that will still drain well.

If you wait untill somewhat late in the spring, yu'll have a chance to see his work under nearly a years full exposure. While that's not the best amount of time to see if he's wrong about the base holding up, it should give you and idea if he's grossly wrong (since the other driveways will start failing).

John

[Pop]

That's bunk; gravel is not a reliable base, it won't hold, and

3-4 years of driving on it -might- have compacted some parts of it some, but not enough, and, well, on the areas where it didn't get driven on much? How did he account for those? Personally, it sounds like cheap work; which is what they got in the final product also.

The

Yes, he could and should have. Your neighbors are going to have sink-holes and low spots starting about three years from now, plus the attendant cracks appearing in the pavement, and they'll continue to sink, especially in the places where people are habitually letting the cars stop or where theyt park. Also if there are rocks under there any bigger than about

4 inches, chances are good they will "float" and begin to appear though the pavement as little but ever-growing bumps until eventually they crack open the pavement enough to let the ice/water finish opening them. My driveway is now 6 years old and is still perfect with one exception: there is a big rock, I'm guessing a foot of so in size, floating up right between the garage doors where they couldn't get the compactor fully into it. The contractor told me he couldn't compact about a three foot area there, but he didn't think it'd matter, and was that OK? I asked what could happen and he said it might rise or sink; no way to be sure, but he didn't think it'd do either. Well, it floated; so far about two inches above the pavement. I pour sealer into the cracks every year, but it keeps on coming up further every spring. And, that area rises and falls with freezing, too, which doesn't happen directly in front of the garage doors. Once I can actually see the rock, I plan to lever it out and fill it with patch, but until then, well, it's not reall in the way of everything. I just have to look at it everytime I hose down the driveway. I'm in far northeastern NY, so our winters are likely worse than yours coldwise, but it's not that much different from where you are.

Oh, also, and it costs a little more, but if you're interested in a nicer looking surface, be sure they put the top-coat on it. Without it, the driveway will start to look like the roadway pretty quickly and it takes tons of sealer when you do decide to apply it. Our "U" part of the drive isn't finished and it takes a LOT of sealer, but the top-coated part takes sealer at the rates listed on the cans. It's an aesthetic thing really, so if that's not important, then no big deal - the surface is actually harder without the top-coating. But dang, it looks great where it's top coated! Oh, the topcoat does seem to keep the edges of the drive from breaking away so easily; forgot that.

HTH,

Pop

[Pop]

PS Actually, a driveway should be slightly above or level with the lawn on at least one side. It should also be sloped, to run rainwater off to areas where it doesn't matter. Like, into the roadway if you have city drains, or in my case, out into a field. But, NOT into the garage! I think they used 1/4" per foot slope on mine, but it's three cars wide. They also put some sort of big, soft fibered thing between the concrete garage floor and the pavement where they meet. I guess it's to allow expansion/contraction with temperature so one doesn't push on the other. Also, the whole job cost about 5k (but that was a few years ago); it's a short but wide driveway with a "U" off to the side.

Pop

Keith Boeheim wrote:

[CWatters]

Everything you ever want to know is on this first rate site...

See Concrete Driveways - full details

In the index on this page...

eg..

Construction

Sub-grade

The surface needs to be dug off to a depth of at least 100mm, or whatever depth is required for the proposed concrete slab. Remove all weeds and other unwanted organic matter. Excavate any soft spots and fill with compacted sub-base material. If the area of the paving is troubled with weeds, it may be necessary to treat the excavated sub-grade with a general weedkiller such as Sodium Chlorate, but it is unlikely any weed will be able to penetrate the upper layers. If an edging is required, this is the point to construct it. Brick edgings, plain or decorative edging kerbs, or cobbles laid lengthways are all suitable. Temporary formwork or shuttering can be used where no decorative edging is required. See also Sub-grades page

Sub-base

Given good ground, mass concrete can be placed directly onto a damp-proof membrane over the prepared sub-grade. For heavier applications, or on bad ground, it may be advisable to construct a sub-base of compacted granular material or lean-mix concrete beneath the actual concrete slab, or to lay a sub-base over a geo-textile. On soft or unreliable ground conditions, a sub-base will help spread the load of a mass concrete slab, but in such conditions it's best to obtain a professional opinion from a civil or structural engineer. Local Authorities will advise on local conditions and reputable companies.

Preparing to Lay

Concrete paths should be 75-100mm thick, whereas drives, garage bases or hardstandings should be at least 100mm thick. For heavier use, such as large vans, use a 150-200mm thick concrete slab. Concrete slabs intended for exceptional loads, such as commercial yards, lorry parks etc., will be at least 200mm thick and should be specifically designed as they will probably require a sub-base of at least 100mm thickness, and steel reinforcing mesh or a fibre-reinforced concrete. The edges of the proposed slab will need to be contained. This can be acheived by means of:-

use of existing walls construction of permanent wall, edging or kerb erection of temporary formwork or shuttering

It is essential that this containment is in place before placing the concrete.

Damp proof membranes

A damp-proof membrane (dpm) should be laid out before placing the concrete. There are numerous membranes available to suit a variety of requirements. Builders' merchants normally carry 'visqueen' or PIFA 1200 as an off-the-shelf product, as it is much used throughout the construction industry.

The purpose of the dpm is two-fold: Firstly, to protect the underside of the slab from attack by dampness and aggresive salts (such as chlorides) or other chemicals in the sub-base or sub-grade, and damaging the concrete, unseen, from beneath. Secondly, a dpm prevents the newly poured concrete from drying out too quickly (de-watering) because of water absorption by the sub-base or sub-grade, which will adversely affect finished strength and can cause hundreds of tiny surface cracks. Any 'laps' required in the membrane should overlap by at least 350mm, and preferably be taped down to prevent ingress of ground water or egress of mix water.

[Keith Boeheim]

Thank for all your advice and input. Surface drainage is not a problem because our garage sits about 7 feet above the road. The driveway is about

22'x60' and we have a culvert, no storm sewers. I see most people using asphalt for the last 10' to 15' to go over the corrugated culvert pipe. Probably less likely to crack and certainly less likely to pit at the street interface where we get lots of salt.

From what I am reading excavation is key because the gravel is a poor subbase. We also have a lot of clay till about 4' down. Finally this contractor that has been putting in most of the driveway is probably not the guy I want.

If I am doing this, is a 6'' slab overkill since I would think that the additional cost would mostly be in material?

What is TOP COAT in an earlier post. Is it different than concrete sealer?

Thank again

kb

[DanG]

I would leave the well compacted gravel. If I were pouring it brand new, I would use gravel sub base by choice. I live where all there is is clay until you get down to the sand rock. The other viable thing to do in heavy clay country is to lime stabilize.

I would pour the street approach in heavier(thicker) concrete and encase the culvert in the pour. Make sure that the asphalt doesn't have something to do with county / municipal barrow ditch maintenance.

The thickness of the concrete is more a function of the loads imposed on the pavement. 6 inch pavement is used in bus and truck pavement.

The quality and longevity of the concrete is more a function of proper grading, proper compaction of subgrade, good drainage to keep the subgrade stable, water/cement ratio of the concrete supplied, good finishing technique, proper curing, and proper joint placement.

I would like to know where you read that gravel is a poor sub grade. I'm sure DOT specifiers would like to know. If you want other professional opinion:

*get other quotes from other local contactors *hire an architect / engineer (probably your best bet for your own peace of mind) *go study here: Some other poster went on and on about top coating and sealing. It seemed obvious to me that he was discussing asphalt.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]

[Lyle B. Harwood]

? If I am doing this, is a 6'' slab overkill since I would think that the ? additional cost would mostly be in material?

Yes.

Any money you spent on additional concrete would be far, far better spent on more surface preparation.

The additional concrete wouldn't do you any good, but more crushed rock, more subbase, or more compaction would.

Best of luck, and let us know how it comes out!

[John]

I thought I killfiled you? Quit changing your email address.

*plonk*