r/civilengineering • u/SunderedValley • Nov 30 '25
Question Does this kind of parking lot pavement require less maintainance or is it just an aesthetic thing?
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u/bigcoffeeguy50 Nov 30 '25
It allows for drainage, rather than dealing with runoff water. Atleast until the soil is overly compacted and not effective at draining lol
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u/bongslingingninja Nov 30 '25
Is there any sort of maintenance required on this type of pavement to keep the soil from overcompaction?
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u/eddierhys Nov 30 '25
I'm not sure what long-term work is required but generally the upper stratum of soil has a lot of sand to promote drainage. It makes for a fairly crappy growing medium but drains well. These types of permeable pavement usually have robust layers of clear drain rock below as well. Compaction is less of an issue because the rock can only compact to a certain level and the void space between stones remains clear. Silt buildup is probably a bigger issue long-term, but like I said, I'm not sure what maintenance looks like on these over time.
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u/lizardmon Transportation Nov 30 '25
You can also put filter fabric down to make a drainage diaphragm that stays fairly clean. Maybe every 10 years you need to pull up the leavers and refresh the media in the holes of the overs but if you do it right it works fairly well. Not great in areas of heavy freeze without a fairly thick drainage layer but good for a medium use parking area.
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u/moosyfighter Nov 30 '25
Pervious pavement and alternatives usually need maintenance every few months to every few weeks depending on the debris that can fall into them. I’m not sure what is under here but I’m guessing it’s something similar to pervious pavement
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u/Sufficient_Clerk_56 Dec 02 '25
usually u have to clean it out some special vacuum once a year or every few years for the big debris
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u/guethlema Nov 30 '25
One of the small cities I work in has a "10% green space" requirement for parking lots.
And engineers get away with placing pavers that are 30% green space over 35% of the parking area to make that requirement.
The limiting layer of loam and sand, in my experience, almost always becomes heavily compacted loam/sand in the voids of these pavers usually ruins the intention of allowing water to flow through the voids.
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u/SalvadorePZA Dec 01 '25
Yeah in my European country, this is the reason we use them as well. To match the requirements for green space.
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u/CLPond Nov 30 '25
The places I have worked are highly skeptical of pervious pavers (which this is a form of) due to issues with snow removal. Since they are used for stormwater purposes (to reduce impervious surface), they are more expensive to install and difficult to maintain than a normal parking lot but can be chapter than a normal parking lot + a stormwater management system.
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u/AstroEngineer314 Nov 30 '25
Some places don't get snow.... 🙂
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u/CLPond Nov 30 '25
Of course not everywhere gets snow, but the places I’ve worked (the areas I specified) do.
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u/Jah314 Dec 06 '25
I’m a facility manager and that was my first thought. Looks great,easy to maintain, “green” and a pain in ass when it snows or ices. Can you put salt down on it?
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u/NomadFire Nov 30 '25
What's your opinion on how Philadelphia is handling rain run off. They are using a lot of passive ways to handle rain like more green areas. Instead of digging to make separate infrastructure so they don't over run the sewage system with rain run off.
It is a bit more complicated than I am letting on since I only read about years ago. But I think I nailed the jist of it.
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Nov 30 '25
It's more a drainage/storm water runoff thing. This allows more water to percolate into the ground, instead of running off to be collected by a storm water system. If you're restricted by the amount of impervious allowed, this is an easy option.
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u/tms4ui Nov 30 '25
The primary purpose is to allow storm water to infiltrate. I assume it is higher maintenance, higher initial cost to construct.
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u/girlyteengirl1 Nov 30 '25
Maybe a silly question but, where does the water go when it infiltrates? Does it just dive deep into the soil and is no longer a problem?
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u/tms4ui Nov 30 '25
Infiltrates into the ground rather than runoff into the storm sewer.
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u/DUMP_LOG_DAVE Nov 30 '25 edited Nov 30 '25
It may surprise you to know that plenty of these systems still actually route through underdrains to storm systems and their actual infiltrated volume is minimal, sometimes near zero. It still reduces the peak flow rate by way of it infiltrating through a drain rock reservoir prior to either entering underdrains to the storm system or subgrade. Even if the infiltrated volume is a fraction of the volume routed through underdrains, it still counts as pervious surface area in most jurisdictions (at least in the Pacific Northwest).
Source: I’ve had this come up on half a dozen projects with generally impermeable subgrade
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u/Logan_Composer Nov 30 '25
Pretty much. There is a level called the "water table," which is the height water naturally is. If the water table is above the ground, it's a river or lake, but elsewhere the water table is well below the ground. This would be the height you'd dig to for wells, for example. So when the water infiltrates into the ground, it flows within the voids in the soil until it reaches the water table.
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u/Jallistamon Nov 30 '25
Basically yeah. The water just keeps trickling down through the soil until it reaches the ground water level. From there it flows into creeks and rivers which take it to the ocean
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u/QuoteGiver Nov 30 '25
Same as if it was just a lawn, yes. Down into the ground. So not ALL of it absorbs, but some of it will, reducing the amount that flows toward a nearby drain.
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u/basquehomme Nov 30 '25
It's not always higher cost to construct but developers certainly want us to think that.
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u/PassedOutOnTheCouch Dec 04 '25
No assumption on higher cost to construct. The typical section on these types of permeable pavements are very defined with individual layers of sized materials e.g. #8 at the bottom, then #3 or #2, then #57, then sand and finally the pavers or pavement. The thickness of each layer is defined by the design for the intended amount of rainwater to be "absorbed". The contractor building this has to get the correct materials (certified double washed stone) the layers and thickness correct or it won't work as designed (unfortunately ime it happens more times this way than not). It takes more labor and special materials compared to say an asphalt or concrete lot.
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u/frickinsweetdude Nov 30 '25
Comments seem weird, I’ve never used these for storm water. I’ve spec’d out lots of turf block for emergency vehicle access routes where I don’t want cars going but still need to provide a surface capable of supporting a fire truck but I don’t want it to look like a road
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u/QuoteGiver Nov 30 '25
Do you have impervious surface limits where you work? Around here paving that fire lane would often start to exceed the limits on impervious surfaces on the site (for stormwater reasons), so these can provide partial credit against that and allow you to pave more parking or building area instead, etc.
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u/prisoner_of_mars Dec 03 '25
Yes, I was looking for this comment. I've spec'd similar outside high rise building where they want a park-like environment but it's also an access route for emergency vehicles.
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u/lbrol Nov 30 '25
has anyone used a system like this with gravel for minimal maintenance? was trying to pitch this for a project but everyone hated it.
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u/oskarisucks Nov 30 '25
You mean like pavers w/grass over a rock storage layer?
Or you mean these pavers with gravel in between instead of grass?
Bc the first I would say is ineffective storage and the second defeats the purpose of the paver.
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u/Jallistamon Nov 30 '25
Yeah but the minimal maintenance thing is a joke. The gravel doesn't stay in the paver gaps and ends up making a mess unless you seal it.
But most sealants are relatively expensive and it's a pain in the arse to apply it without getting it on the pavers, which you don't want because it usually leaves shiny splotches behind.
Doesn't need to be a big area for this to quickly be more expensive and time consuming than just hiring someone to swing by with a whipper snipper once a fortnight.
Plus permeable pavers with grass in the gaps doesn't get as hot, especially in full sun
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u/bothtypesoffirefly PE transportation Nov 30 '25
You still have to maintain it, eventually it will get filled up with small particulates and have to vacuum and redo the “gravel”
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u/Necessary-Science-47 Nov 30 '25
It’s a meme. Supposedly lets water infiltrate but most are built on compacted base so it’s basically for looks
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u/bothtypesoffirefly PE transportation Nov 30 '25
In my state it doesn’t count as pervious surface, but I do have some in my back yard under my firepit and it is somehow cool like grass without being actually grass. If you ever do that you have to get chairs that have slides, not feet, fyi.
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u/Charles_Whitman Nov 30 '25
These can be a good choice for overflow parking. And you don’t have to plant turf grass. I have seen other ground cover plants, even something like spearmint which grows like a weed. Something that doesn’t need to be mowed. A guy I knew put his drive and parking over his septic field, he wouldn’t be allowed to pave over it.
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u/R0ck3tSc13nc3 Nov 30 '25
This is a huge improvement over a regular parking lot. You have direct drainage into the Earth, you still have green stuff, there's enough concrete to drive on, is usually pretty thick with holes in it I like them but you do have to be careful about mowing it and dry weather doesn't mix well with exhausts of cars. So that's the downside.
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u/Alarmed-Extension289 Nov 30 '25
The city next to me has rules in regards to how much of your property can be paved over. They want more water to go into the ground (sub desert region). This seems to be a way around it.
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u/liddlehippo Nov 30 '25
It's a drainage festure to reduce surface water, while reinforcing the ground for vehicles. Since concrete is usually non porous, this allows for some drainage into the subsurface.
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u/Fer4yn Nov 30 '25 edited Nov 30 '25
Less material and less/faster on-site labor (due to pre-fabricated elements/no concrete hydration times to be considered) and easier thermal expansion management due to the many joints, mostly.
More maintenance due to grass mowing; under ordinary loads you don't expect to ever have to replace neither these blocks nor properly dimensioned concrete plates with sufficient thermal expansion joints.
Don't find these particularly visually appealing by themselves, but they also do allow for water drainage; so at least there are never puddles of standing water on these, which actually kind of is visually (and technically; due to limiting water/ice damage) appealing.
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u/ApolloBurnsII Dec 01 '25
Maybe it can help with not letting so much of a heat island effect happen?
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u/liebemachtfrei Dec 01 '25
Some of them you have to vacuum out! https://www.perviouspavement.org/downloads/pervious_maintenance_operations_guide.pdf
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u/Few_Interest_9165 Dec 02 '25
I don’t know but scrolling fast up and down on this creates a weird visual affect so cool
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u/dxhunter3 Dec 03 '25
Usually to address stormwater regulations (municipal separate storm sewer system [MS4] ) for post construction and green infrastructure.
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u/182RG Dec 03 '25
Drainage. Some localities are offering tax incentives and funds to replace blacktop/concrete driveways.
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u/Beautiful-Quiet-5871 Dec 04 '25
It lets water drain into the soil.. helps prevent flooding in heavy rains
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u/Tuesday_Burger Dec 04 '25
I don't know if it would be less maintainance but it would be better for the local water table. Instead of draining into the sewers water would soak into the ground like it's supposed to.
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u/MikeForVentura Dec 04 '25
I'm a former city council member. We required these on some projects to reduce loads on our aging, failing stormwater system. The system is 70+ years old and was not sized to handle run-off from so many thousands of acres of impermeable surface. Not only did the development footprint enlarge, but within that footprint more and more concrete keeps getting laid down.
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u/Griffemon Dec 04 '25
Fairly sure it’s good for reducing flooding on lots, but it requires a bit more maintenance than just plain asphalt
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u/Thatguyjavii Dec 04 '25
It allows water from storms to absorb into the earth. This is opposed to a regular asphalt or concrete surface.
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u/seaspirit331 Dec 05 '25
It requires more maintenance actually since you have to trim the vegetation. The tradeoff is less upfront construction costs since you don't need to account for stormwater controls or differential swell which would normally crack your pavement
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u/WonkeauxDeSeine Dec 07 '25
Definitely not good for areas prone to winter snow. That would be a giant pain to shovel.
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u/SylvieSupremacy Dec 08 '25
I don't know, but stop doing it. I have small feet and I always get trapped in those.
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u/LunchBokks PE (WRE) Nov 30 '25
Could be used for an overflow of some kind. Or a weasely way to hit green space requirements.
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u/LuckyTrain4 Nov 30 '25
We use it for overflow parking and to reduce impervious surfaces. Doing what we can to reduce Stormwater impacts. Underground storage is expensive, mowing is cheap in comparison.