Parking pad suggestions in compacting and gravel

[nickclifford]

hi all, I'm constructing a parking pad and discounted concrete as too much money. If I intend to live here for ever I'd drop the cash but think we'll be moving in about 5yrs or so in preparation for retirement. Anyone been through same thing and have any thoughts on what's best ? Thanks

[Protagonist]

Originally Posted by nickclifford

Attachment 297524 hi all, I'm constructing a parking pad and discounted concrete as too much money. If I intend to live here for ever I'd drop the cash but think we'll be moving in about 5yrs or so in preparation for retirement. Anyone been through same thing and have any thoughts on what's best ? Thanks

I've designed driveways and roads made out of graded crushed stone, back when I still worked for the Corps of Engineers. What I'm going to describe here is not a design, per se, but rather just detailed guidelines. This should at least give you a starting point for talking to local contractors and stone suppliers.

First of all, never call it "gravel." No telling what you'll get, including possibly rounded river rocks that will never compact properly. You want to use "graded crushed stone aggregate." Remember that phrase, and use it. Good gradations to choose from are #57 and #411, depending on how porous you want it to be for drainage. #57 gradation is more porous because it contains less dust and fine sizes, but #411 makes a better finished surface. So a layer of #411 over a layer of #57 gives you a better product than using either one alone.

You also want the stone to be angular, with the longest dimension no more than twice the shortest dimension for any given piece of stone. This provides the best interlocking during compaction. So if you want to look knowledgeable, pick up a sample in your hand. Look for sharp edges and stone as close to cubical as possible. Both are good.

As for material, limestone is a good choice, or granite if it's common enough in your area to be price-competitive. Regardless, you want hard, durable stone that won't fracture when compacted.

As for compaction, roller compaction is quick and effective for long driveways, but vibratory compactors will get into corners and edges better, even though they take longer. In any event, never spread the aggregate with a bulldozer or grader blade, because using a blade to spread the material ruins the gradation, causing the fines to settle and the larger stones to rise to the top.

For best load-bearing, excavate about 12" if you want your driveway to be flush with the surrounding ground. Compact the soil after excavating but before adding stone. Then add a 6" layer of #57 graded crushed aggregate, compact it, and then top it with a 6" layer of #57 or #411, and compact it again.

You can add a sprayed-on asphalt or coal tar seal coat to help bind the aggregate together, at lower expense than asphalt pavement (works better with #411 gradation than with #57). Of the two possible seal coats, coal tar is more resistant to spilled oil and fuel than an asphalt seal coat, because asphalt is a petroleum product, and oil or fuel will act as a solvent to dissolve the seal coat. Coal tar, being a coal product, is less likely to dissolve or melt when oil or fuel is spilled on it.

[HowieE]

May I suggest you crown the excavation to aid in drainage before adding the stone. If you have the grading you might want to lay perforated piping along the edge to move any water that percs down through the store away. Lay the piping with one row of holes pointing downwards and cover the top row of holes with construction paper.

I used this approach under an asphalt roadway and you will be amazed at the water that will flow from under the pad.

Reduced water and reduced frost heaving.

[nickclifford]

good info on the type of stone, I'll go to quarry today and ask those questions.
I don't want to dig down any further so will compact and build up from where it is now, but need to deal with the transition from gravel to soil. This is not going to be 100% perfect but I'm using a local trustworthy tractor guy to assist.

when you say "never spread the aggregate with a bulldozer or grader blade" , if the rock is being dumped from a truck, then how should we spread, by hand with rakes ?

[nickclifford]

Originally Posted by Protagonist

I've designed driveways and roads made out of graded crushed stone, back when I still worked for the Corps of Engineers. What I'm going to describe here is not a design, per se, but rather just detailed guidelines. This should at least give you a starting point for talking to local contractors and stone suppliers.

First of all, never call it "gravel." No telling what you'll get, including possibly rounded river rocks that will never compact properly. You want to use "graded crushed stone aggregate." Remember that phrase, and use it. Good gradations to choose from are #57 and #411, depending on how porous you want it to be for drainage. #57 gradation is more porous because it contains less dust and fine sizes, but #411 makes a better finished surface. So a layer of #411 over a layer of #57 gives you a better product than using either one alone.

You also want the stone to be angular, with the longest dimension no more than twice the shortest dimension for any given piece of stone. This provides the best interlocking during compaction. So if you want to look knowledgeable, pick up a sample in your hand. Look for sharp edges and stone as close to cubical as possible. Both are good.

As for material, limestone is a good choice, or granite if it's common enough in your area to be price-competitive. Regardless, you want hard, durable stone that won't fracture when compacted.

As for compaction, roller compaction is quick and effective for long driveways, but vibratory compactors will get into corners and edges better, even though they take longer. In any event, never spread the aggregate with a bulldozer or grader blade, because using a blade to spread the material ruins the gradation, causing the fines to settle and the larger stones to rise to the top.

For best load-bearing, excavate about 12" if you want your driveway to be flush with the surrounding ground. Compact the soil after excavating but before adding stone. Then add a 6" layer of #57 graded crushed aggregate, compact it, and then top it with a 6" layer of #57 or #411, and compact it again.

You can add a sprayed-on asphalt or coal tar seal coat to help bind the aggregate together, at lower expense than asphalt pavement (works better with #411 gradation than with #57). Of the two possible seal coats, coal tar is more resistant to spilled oil and fuel than an asphalt seal coat, because asphalt is a petroleum product, and oil or fuel will act as a solvent to dissolve the seal coat. Coal tar, being a coal product, is less likely to dissolve or melt when oil or fuel is spilled on it.

one more quick question on compacting, how much weight is needed and are those rollers filled with water ok? thx

[Protagonist]

Originally Posted by nickclifford

one more quick question on compacting, how much weight is needed and are those rollers filled with water ok? thx

Water-filled rollers are usually fine.

The actual weight required will vary depending on soil conditions and other factors, so there is no single answer.

By the way, of you're placing the stone on top of the soil and not excavating, try to make the bottom layer about a foot wider on each side than the top layer. That will allow you to shape the sides at a shallower slope when the stone assumes a "natural angle or repose."

And one more piece of advice, for parking your Airstream, try to make the top layer at least 12 feet wide. More wiggle-room that way, and enough reasonably flat surface at the top to work on tires and such while the trailer is parked.

[Protagonist]

Originally Posted by nickclifford

when you say "never spread the aggregate with a bulldozer or grader blade" , if the rock is being dumped from a truck, then how should we spread, by hand with rakes ?

Front-end loader bucket will usually let you move the aggregate around by scooping it up where there's excess and dumping it where there's not enough, without messing up the gradation too much. The loader bucket can also provide some initial compaction by pressing down with the flat bottom of the bucket after placing the stone.

Also, the truck shouldn't dump it all in a high pile at one spot. It should start at the far end of the drive, and roll forward as it dumps, to make a long, low pile that's easier to spread.

[nickclifford]

Originally Posted by Protagonist

Water-filled rollers are usually fine.

The actual weight required will vary depending on soil conditions and other factors, so there is no single answer.

By the way, of you're placing the stone on top of the soil and not excavating, try to make the bottom layer about a foot wider on each side than the top layer. That will allow you to shape the sides at a shallower slope when the stone assumes a "natural angle or repose."

And one more piece of advice, for parking your Airstream, try to make the top layer at least 12 feet wide. More wiggle-room that way, and enough reasonably flat surface at the top to work on tires and such while the trailer is parked.

We have excavated but being on a slope it's rather complicated to explain, ideally we would go further down so there's a smooth natural transition from the dirt onto the pad. I've got a nice width at 18' but my biggest challenge is backing up a fairly steep slope, I know it's possible using my local Tow service company but hoping I can do myself with a Tundra in low gear. Once the rains set in, too slippery unless i install those plastic driveway sections I've seen used on slopes ... thanks for all your input, much appreciated.

[CRH]

I boxed in the low side with railroad ties and filled the area with what we call crusher run. It is two ties high on the low side. I smoothed it by hand with a rake. I let it get rained on a few times before putting my trailer on it. It is now very hard. You can't take a spade and dig a hole in it.

[gklott]

Recommend using what we did for an ideal, permeable parking or driveway surface: TrueGrid https://www.truegridpaver.com/

Level the area, put down a 2 inch of road base, lay down the TrueGrid pavers, and fill in the pavers with smaller stones, dirt with grass, etc. The City of Austin uses the "industrial" version for city parking lots. The residential grade is perfect for your Airstream.

73/gus

[dznf0g]

Similar to What I used

https://www.ndspro.com/ez-roll-grass-pavers

[nickclifford]

Originally Posted by gklott

Recommend using what we did for an ideal, permeable parking or driveway surface: TrueGrid https://www.truegridpaver.com/

Level the area, put down a 2 inch of road base, lay down the TrueGrid pavers, and fill in the pavers with smaller stones, dirt with grass, etc. The City of Austin uses the "industrial" version for city parking lots. The residential grade is perfect for your Airstream.

73/gus

very cool, that's what I was thinking for the sloped area so I could move the trailer in rainy season if needed. I'm on clay & a high water table, we can get hammered in the Santa Cruz mountains during rainy season. thx

[MelGoddard]

ME?
I would not use gravel, stone, or any of the aggregates.
They hold moisture, and parking on it would have the same effect as parking on grass.
The vehicle will rust three times faster than normal; due to the moisture content.
On grass, is moisture, but also higher oxygen content due to the vegetation.
(Two RV dealers told me that; don't do it.)

My 30' FC is parked on a dedicated concrete pad; with the wheels off the concrete by boards on one side, and plastic kitchen cutting boards on the other. (the pad is slightly tilted for drainage.)

[dznf0g]

I also park on Concrete, but the approach from the street to the pad is EZ Roll permeable grass paver:





I knew kids would come in handy one day......

[nickclifford]

Originally Posted by MelGoddard

ME?
I would not use gravel, stone, or any of the aggregates.
They hold moisture, and parking on it would have the same effect as parking on grass.
The vehicle will rust three times faster than normal; due to the moisture content.
On grass, is moisture, but also higher oxygen content due to the vegetation.
(Two RV dealers told me that; don't do it.)

My 30' FC is parked on a dedicated concrete pad; with the wheels off the concrete by boards on one side, and plastic kitchen cutting boards on the other. (the pad is slightly tilted for drainage.)

Agree, in an ideal world I'd use concrete but I'm moving in about 5 yrs and don't want to drop the $6k or so, plus I got two kids going to college soon ... [emoji30]

[Protagonist]

Originally Posted by MelGoddard

I would not use gravel, stone, or any of the aggregates.
They hold moisture, and parking on it would have the same effect as parking on grass.

Aggregates do not hold moisture unless the soil sub-base has not been properly prepared, or you've used the wrong stone gradation. Properly graded aggregate on a sub-base that is sloped for drainage dries faster than just about any other pavement surface. Any rainfall landing on the aggregate immediately filters down to the sub-base then drains off. There should be no ponding of water under the surface.

Perhaps you meant that it would be more humid above an aggregate surface immediately after a rain, which is true. Crushed aggregate has a lot of surface area compared to concrete or asphalt pavement, and more wetted surface area means faster evaporation. So for a brief period of time after a rain, the air above the aggregate will be more humid. But that's not the same as "holding moisture."

[Tincampers]

Originally Posted by Protagonist

Aggregates do not hold moisture unless the soil sub-base has not been properly prepared, or you've used the wrong stone gradation. Properly graded aggregate on a sub-base that is sloped for drainage dries faster than just about any other pavement surface. Any rainfall landing on the aggregate immediately filters down to the sub-base then drains off. There should be no ponding of water under the surface.

Perhaps you meant that it would be more humid above an aggregate surface immediately after a rain, which is true. Crushed aggregate has a lot of surface area compared to concrete or asphalt pavement, and more wetted surface area means faster evaporation. So for a brief period of time after a rain, the air above the aggregate will be more humid. But that's not the same as "holding moisture."

I need to get you up here to fix my driveway. We get run off from the road and in a heavy rain it will wash it out. I've been working on drainage along the sides and it is starting to help.

[StrmyWeather]

Protagonist gives some great advice. I needed a parking pad next to our driveway because of the number of drivers in the family. I bordered the area with concrete and made the pad about 8" deep. I compacted the area using a vibrating compactor; easy to manage and works great. We then laid geotextile material over the dirt (heavy landscape material) filled partially with 57, (we used crushed concrete) compacted again, and continued until filled. The rock really locks together. It gets used a lot more than trailer parking area would and I haven't had to rake the rocks in the 10 years it's been installed. Good luck with your build.

[Protagonist]

Originally Posted by Tincampers

I need to get you up here to fix my driveway. We get run off from the road and in a heavy rain it will wash it out. I've been working on drainage along the sides and it is starting to help.

HowieE's suggestion, digging a trench along each side, putting down an aggregate bed, laying a properly-sloped perforated pipe, and covering it with more aggregate, basically puts a French drain on each side of the driveway, and will do wonders for improving the drainage.

But in your case, I would consider placing a cattle guard close to where the driveway leaves the road— even if you don't have cattle— and use that cattle guard as a bridge over a sloped trench across the driveway to carry runoff from the highway off to whichever side is lower, so that the highway runoff doesn't use your whole driveway as a French drain.

[Protagonist]

Originally Posted by Protagonist

But in your case, I would consider placing a cattle guard close to where the driveway leaves the road— even if you don't have cattle— and use that cattle guard as a bridge over a sloped trench across the driveway to carry runoff from the highway off to whichever side is lower, so that the highway runoff doesn't use your whole driveway as a French drain.

Strange to be quoting myself, but here's something else that may help if you can't find prefabricated cattle guards strong enough to support your trailer— three drawings from the Federal Highway Administration for building a cattle guard that's strong enough to drive construction equipment over, so it should hold up to your Airstream's traffic, too. You wouldn't need the wing guards on the first drawing unless you're placing it at a fence line.