My office's parking lot is asphalt. Near the bottom of the driveway portion, downhill from the main parking lot, the surface is dipping a little bit where a culvert crosses under the driveway. We share the lot with the building next door.

We have been looking into options for repair. The lot has a few other small potholes and several cracks, but the main issue is the dip.

Costs aside, would you recommend going with concrete or asphalt to replace what's there? And why?

Concrete done properly will usually outlast asphalt by a fair margin.

If the dip is over the culvert I suspect the issue is due to settling. Concrete would also fail in this situation. Regardless of which route you go that will need to be addressed first.

Sounds like you need a concrete apron over the culvert, rather than a whole new parking lot.

And maybe a new, stronger culvert while you're at it.

Thanks for the feedback.

We also believe that washout/settling around the culvert is the culprit. The buildings/parking lot are 20-25 years old.

We've made sure that contractors we've been in touch with have agreed to repair the culvert area prior to resurfacing.

Has code for the parking lot entrance changed? Concrete may be the only option due to code changes.

As has already been said replace or repair the culvert. What's on top is only as good as what's underneath.

Man, I didn't even think about codes. Thanks for the heads-up on that!

quote:

Originally posted by Mustang-PaPa:
Has code for the parking lot entrance changed? Concrete may be the only option due to code changes.

As has already been said replace or repair the culvert. What's on top is only as good as what's underneath.

Codes and permits can get ya. Not knowing where this is was my reason for asking. Some areas are relaxed and some can be a real pain.

If strict you might get by with leveling out the dip no problem but if it goes any further new code changes may get ya.

Just ask to be safe.

Be ready for a serious sting from the permitting dept.

We are trying to figure out a way around it. The fees, plans, etc they want to resurface one of our parking lots, is about as much as the actual job.

Before deciding on the surface, I would investigate what is causing the dip. It may be settling but it may be something else.

If the culvert is cracked or if there is a separation of pipe joints, you may have water and subbase (or soil) leaking into the culvert causing voids under the pavement. If you do not fix the leakage, this will cause problems for any payment material you pick.

Can you see through the culvert pipe with a flashlight just to get some idea of its condition?

Last drive I had quoted concrete was 3 times the cost of asphalt.

So far, the city requires no permits (small conservative town in SC, YAY!). We have been forwarded to the SC DOT since the parking lot accesses a 2-lane highway.

I can't get down to the culvert and haven't looked into it; it drains into a retention pond. For that matter, I don't even know if there really is a culvert there, now that I think about it, but that's what I've been told by the guy who does our landscaping. Next dry day, I'll try and take a look at it.

The quotes actually aren't that bad, compared to what I was expecting.
Asphalt: 2 quotes - $42,135 and $18,700. The $42k quote company has a very good reputation.
Concrete: $19,225

quote:

Originally posted by AUTiger89:
The quotes actually aren't that bad, compared to what I was expecting.
Asphalt: 2 quotes - $42,135 and $18,700. The $42k quote company has a very good reputation.
Concrete: $19,225

something is very crazy about those quotes. Concrete is almost always some multiple more expensive than asphalt. And having two different quotes for asphalt where one is more than double the other makes me suspect they are not quoting anything like the same thing. Things to get clear are thickness and number of lifts. The high dollar one may be quoting a thicker mat and multiple lifts while the cheaper one may be quoting one single thin lift.

Sorry, I should have clarified. The concrete quote is only for the driveway portion of the parkimg lot, not the whole lot.

The asphalt quotes are for the whole lot.

I'll check into the lifts.

We have a lengthy concrete driveway 2.5 cars wide. The only problem area is where it goes over the culvert at the road, which is common here. Settling and eventual washout will crack the concrete and cause it to lift. Eventually it will look like a pile of dominos.

As mentioned above the quotes you’ve received are not comparable. I understand one is for the driveway and one for the parking lot.

Things I would look out for and should be spelled out include:

1. Are they going to completely remove the existing surface or just go over it?
2. Will they improve the base? The construction of the base is the single most important aspect of a job like this.
3. Are they going to address any issues with drainage?
4. What type of asphalt and what thickness? Conversely what strength of concrete and what thickness?
5. You mentioned that you’re going to have DOT involved. This is a good idea and be sure you understand exactly what they are requiring. This info needs to be relayed to the bidders before getting any estimates.


On an apples to apples comparison concrete is usually 2x to 3x more expensive. It depends on what kind of traffic you get. Are there any large trucks? Or is it just vehicular traffic?

A lot of unknowns…

Well, we had it done over the weekend. Everything looks great. Went with concrete. Cost us just under $20k, but they just did the driveway entrance and not the whole parking lot.

We had it in the contract that they had to repair the drainage pipe under the driveway if it was damaged, but to my understanding, they didn't have to repair that. They removed the existing surface before they laid the concrete. I don't know the thickness. Fortunately, since it didn't touch the highway, we didn't have to get any permitting from the DOT or the city (we're inside city limits).

So I'm satisfied at this point.

I’m late now that it is already done, and it probably doesn’t matter anyway.

Depending on how deep a culvert is and how problematic the drainage is, one option is to slurry around the culvert pipe rather than compacting base or other material to make your subgrade, then put your surface over that.

Likely what happened is that when the culvert was originally installed they didn’t get perfect compaction of the fill. (I’m sure somebody has managed it once, somewhere, but I don’t think I’ve ever seen it.). Over the years, with people driving over it year round, it has been compacted better than it was, resulting in the dip. (Nice thing about asphalt in this situation is it can stretch a little where concrete would break.) As long as they only removed material before putting down the concrete, it should be nice and tight. If the put base down underneath hopefully they did a great job on the compaction.

I’ll bet it will be fine.

Our house sits on a small acreage. There’s a culvert where the driveway intersects with the road out front. We hired the G.C. to build our house, and were involved from the beginning in numerous choices. He didn’t even talk to us about the concrete approach over the culvert, just had it poured because that’s the right thing to do.

There are a few neighbors who have asphalt. Those who have dumpsters for their trash (especially) are seeing the asphalt crumble from the trash truck repeatedly crossing.

I just found out - it's 6" thick, capable of handling 5,000psi.