Quick answer
Permeable pavers, or permeable interlocking concrete pavement (PICP), are concrete pavers laid with open joints filled with small stone over a stone reservoir, so rain passes through the surface and soaks into the ground or drains slowly away.
The pavers are not permeable themselves; water moves through the joints. The system only works when the layers beneath are clean, open stone and the soil or an underdrain can take the water. Sediment clogging is the main failure.
Quick facts
The key facts about Permeable Pavers, with sources:
- How water moves
- Through stone-filled joints into open-graded stone layers, then into soil or an underdrain 12
- Joint fill
- Small angular stone (ASTM No. 8, 89 or 9), not ordinary sand 1
- Surface slope
- Less than 12% and typically 5% or less 1
- Water table
- More than 2 ft from the bottom of the base to the seasonal high water table 1
- Wells
- At least 100 ft from water supply wells, and local rules may add more 1
Key takeaways
- Water goes through the joints, not the pavers. The joints are filled with small stone, never with standard joint sand.
- The system is a stack of open stone over soil. Its job is to store and release water, so soil, slope and groundwater decide whether it fits.
- Clogging by dirt is the main failure. Vacuum sweeping at least twice a year keeps it working, per two county guides.
- It does not suit contaminated runoff, heavy traffic, steep slopes or yards that shed soil onto it.
- Design is engineered work. Ask for a site assessment and check local stormwater rules before you buy.
What permeable pavers are, in plain terms
A permeable paver surface looks like an ordinary paver patio, but it behaves like a filter.
The EPA lists interlocking pavers among permeable pavements, which it says can help reduce runoff by infiltrating rain water and melting snow 4.
Fairfax County explains the key point: in a permeable interlocking system, the pavers are not permeable themselves. Water moves through joints filled with small aggregate 2.
The Interlocking Concrete Pavement Institute (ICPI) says permeable interlocking concrete pavement is recognized by federal and state stormwater and transportation agencies as a best management practice and a low impact development tool to reduce runoff and water pollution 1.
That is an industry statement about agency recognition. Whether your city counts it toward stormwater rules is local.
This is different from a standard paver patio, where water runs off the surface. See interlocking concrete pavers for the unit and the hardscape base specification for a conventional base. Permeable systems use a different, open stone base.
How the layers handle water
ICPI’s Tech Spec 18 lists the parts. Pavers have molded joints or openings filled with angular stone.
Below is a 2-inch open-graded bedding course, then an open-graded base reservoir, usually 4 inches of ASTM No. 57 stone, and where needed a subbase of larger stone 1.
Fairfax County says the aggregate base temporarily stores water, supports the surface and filters pollutants 2.
Where the water goes next depends on the soil. ICPI describes three designs. Full infiltration sends water into the soil and is most common over sands and gravels.
Partial infiltration adds perforated drain pipes and suits silts and clays. No infiltration is required where soil has very low permeability or low strength, and it uses an impermeable liner and a controlled outlet 1.
The saturated subgrade’s infiltration rate sets how much can drain into the ground. ICPI says the subgrade is generally not compacted, because that can substantially reduce infiltration 1. That is the reverse of a conventional patio, where ICPI says subgrade compaction is critical 5.
- Concrete paversAt least 3 1/8 in. thick for vehicles; 2 3/8 in. for pedestrian use
- Permeable joint stoneAngular ASTM No. 8, 89 or 9
- Open-graded bedding courseAbout 2 in. of ASTM No. 8 stone
- Open-graded base reservoirTypically 4 in. of ASTM No. 57 stone; 6 in. minimum for pedestrian use
- Open-graded subbaseLarger stone; thickness set by storage and load; may be omitted for pedestrian use
- Geotextile (design option)Separates stone from soil; required along sides
- Subgrade soilGenerally not compacted; an underdrain may be added over slow soils
Thicknesses are ICPI’s typical values for a design, not a recipe for any one yard. Source: [1]
Will it fit your site? The limits ICPI lists
| Site factor | What ICPI says | What it means for a yard |
|---|---|---|
| Surface slope | Less than 12%, typically 5% or less 1 | A steep slope needs terracing or another surface |
| Water table | Estimated depth from the bottom of the base to the seasonal high water table greater than 2 ft 1 | Wet, high-water sites fail the test |
| Contributing runoff | Runoff from hard surfaces draining onto it does not exceed five times the paver area 1 | Roof or driveway runoff onto a small patio can overload it |
| Sediment source | Runoff draining onto it should not come from soil erosion, exposed topsoil or mulch 1 | Bare soil or mulch beds uphill will clog it |
| Wells | At least 100 ft from water supply wells; local rules may add more 1 | Check well and septic setbacks |
| Foundations | Down slope of building foundations that have piped drainage at the footers 1 | Do not drain toward a basement |
| Contamination risk | Not for stormwater hotspots such as fueling or fleet areas 1 | Not for a work yard with spills |
| Maintenance | Sites where the owner can meet maintenance requirements 1 | Needs a plan to vacuum sweep |
| Traffic | Best suited to light traffic under 35 mph 2 | Fine for a patio, walk or driveway; not for heavy vehicles |
What the system cannot do
It cannot clean dirty runoff for you if the pavers are fed soil, mulch or spills, and it cannot drain a site with a high water table or no outlet.
ICPI says subgrade soil, water table and drainage design set the outcome 1. A civil engineer or stormwater professional designs these systems for larger or sensitive sites.
Example: the five-times test on a small patio
The patio size and the roof are invented to show the arithmetic. The limit is ICPI’s: runoff from hard surfaces draining onto the pavement should not exceed five times its area 1.
| Step | Example input | Result |
|---|---|---|
| Permeable patio area | 300 sq ft | Limit on contributing hard area: 5 × 300 = 1,500 sq ft 1 |
| Roof draining onto it | 900 sq ft of roof, sending its downspout water to the patio | 900 is under 1,500, so it passes this one test |
| Add a driveway apron that also drains onto it | 800 sq ft | 900 + 800 = 1,700, which is over 1,500, so it fails the ratio |
| Check the water table | Seasonal high water 1.5 ft below the base bottom | ICPI says more than 2 ft; this one fails 1 |
Passing one test does not approve a design. A soil infiltration check and local stormwater rules come next. Use the drainage diagnostic to look at how water behaves on your lot before you plan.
Where you meet the term: bids, stormwater credits and city rules
On a landscape bid. “Permeable paver patio” should list the paver, joint stone, bedding stone, base and subbase depths, geotextile and any underdrain. A bid that shows ordinary sand joints or a compacted dense base is not a permeable system. See the landscaping estimates guide for how to compare lines.
In stormwater programs. ICPI says permeable systems can earn landowner credits on stormwater utility fees 1. Whether your city offers one, and what it requires, is local. Ask the stormwater office.
In city specifications. Many cities and counties publish design and maintenance sheets. Fairfax County and Howard County, Maryland, are two examples 23.
On the service page. The patios and walkways page covers the service. The hardscape drainage page covers drainage for paved areas in general.
What the system offers, and what it costs you in care
What the sources credit it with
Limits and burdens
Limits of the evidence, including frost
Most of the technical detail here comes from ICPI, which represents the industry. Tech Spec 18 is a construction bulletin for contractors and inspectors, and it sends designers to the ICPI manual and to ASCE standard 68-18 for design 1. Its numbers describe typical designs, not a plan for your yard.
Cold climates are the common worry. The CMHA’s project summary on a University of New Hampshire study says stormwater agencies and engineers had resisted PICP in cold climates, citing risks of heaving, freeze-thaw damage and slowed or blocked surface infiltration, and concerns about maintenance and snow removal 6.
We did not load the study’s results, so we state no finding either way.
ICPI says the units resist freeze-thaw and deicing salts, and that installation can continue if the subgrade and aggregates stay unfrozen 1.
We did not find an extension source that tests permeable pavers on home patios in clay, so claims about clay yards come from ICPI’s own partial-infiltration and no-infiltration designs only 1.
Maintenance advice differs by place. Fairfax and Howard both say to avoid washing or power washing, but local manuals and manufacturers may differ. Follow the guidance for your system.
What drives the price, and how long it lasts
We do not publish prices. A permeable system usually calls for deeper excavation than a standard patio, more stone, geotextile, and sometimes underdrains and an overflow route. Soil testing, engineering and permit costs can add to a total. Low-infiltration soils push the design toward underdrains or no-infiltration versions, which are heavier work 1.
ICPI lists a 50-year design life for the paver surface based on field performance 1. That is a trade-body figure for the units, and it says nothing about the clogging of the base or joints, which depends on upkeep. We give no lifespan for a whole system.
Ongoing costs include vacuum sweeping at least twice a year and joint stone top-ups 23. Use the cost hub to see what shapes a bid.
How a permeable paver job runs
The is below a design-and-build job. Larger or sensitive sites usually involve a civil engineer, and many cities require review.
- Check local rules first. Ask your stormwater office whether a permit, a design standard or a drainage plan applies.
- Assess the site. ICPI says the assessment includes soils maps, the NRCS hydrologic soil group, any fill or compaction history, drainage patterns, wells and land uses draining onto the site 1.
- Call 811 before excavation so buried lines are marked.
- Keep construction dirt out. ICPI says preventing sediment from entering the aggregates and surface during construction must be the highest priority, and mud from vehicles is a main source 1.
- Build the layers. Place geotextile where designed, then the subbase, base and bedding stone, each compacted as the design says 1.
- Place pavers and fill joints with stone, then sweep the surface clean 1.
- Plan the upkeep before you hand over the keys: who vacuums, how often and where snow goes.
Overflow must go somewhere legal
Underdrains and overflow pipes must lead to a lawful outlet. Never send runoff onto a neighbor or into a sanitary sewer. Call 811 before digging, and have an engineer review any design that sits near a foundation, a well or a septic system.
Keeping the surface open
Upkeep tasks are listed here without fixed dates. Frequency depends on the debris the site produces.
- Vacuum sweep at least twice a year. Fairfax and Howard counties both say so 23.
- Keep it clear of debris. Fairfax says to keep surfaces free of trash, sediment and debris 2.
- Do not sand, seal, resurface or power wash. Fairfax lists all four as things to avoid 2. Howard also says washing systems and compressed air units should not be used 3.
- Do not store snow piles with sand, mulch or soil on it. Fairfax says to avoid both 2.
- Plow carefully. Howard says set blades one inch higher than normal and do not push plowed snow or snowmelt onto the pavement; use deicers in moderation 3.
- Test after rain. After sweeping, Fairfax says to pour a five-gallon bucket of water on the surface to see if it soaks in 2.
Warning signs of clogging, and when to call a pro
- Standing water on the surface. Fairfax links stained or clogged pavement to ponding and says to do restorative vacuuming 2.
- Water still in the observation well 72 hours after a half-inch storm. Fairfax treats this as a clogging sign 2.
- Slumping, cracking or broken pavers. Fairfax lists these as signs of surface deterioration to repair or replace 2.
- Mud washing onto the surface. Fix the source, such as bare soil upslope. ICPI says erosion and mulch runoff should not drain onto it 1.
- Heavy trucks tracking dirt. Howard says grit ground into the surface leads to clogging and early failure 3.
If water backs up near a foundation, call a drainage contractor or civil engineer. See also yard ponding and standing water.
Rules and standards that apply
Design standard. ICPI points to the ASCE permeable interlocking concrete pavement standard 68-18 and its own manual for design 1. The standard is voluntary until a city or contract adopts it.
Local stormwater rules. Cities and counties set stormwater and permit rules. Fairfax says its fact sheet is not intended to determine maintenance responsibility 2. Howard says maintenance agreements should clearly specify routine tasks 3.
Setbacks. ICPI recommends at least 100 ft from water supply wells and says local jurisdictions may add guidance or rules 1.
HOA and utility fees. Some neighborhoods limit paved area, and some cities offer fee credits. Ask your HOA and the stormwater office.
Permeable pavers compared with nearby terms
| Term | How it handles water | Joint fill | Where to read more |
|---|---|---|---|
| Permeable interlocking pavers | Water passes through joints into open stone 21 | Small angular stone 1 | This page |
| Standard interlocking pavers | Sheds water to edges and drains | Sand, per ICPI Tech Spec 2 5 | See paver joint sand |
| Gravel path | Water soaks in through loose stone | None | See gravel path vs. paver path |
| Pervious concrete or porous asphalt | Water passes through the surface into soil and gravel layers below 4 | None | Not covered here |
| Dry well | Holds and releases roof or yard runoff underground | Stone-filled pit | See dry well |
- Under 12%Surface slope limitTypically 5% or less 1
- Over 2 ftBase bottom to seasonal high water table1
- 100 ftMinimum distance from water supply wellsLocal rules may add more 1
- 5 to 1Maximum ratio of contributing hard area to paver area1
Source: [1]
Common permeable paver myths
- Myth Any paver patio drains into the ground.
- Reality Ordinary pavers shed water. Only a system with open joints over a stone reservoir infiltrates, and the pavers themselves are not permeable 21.
- Myth Use regular joint sand and it will still drain.
- Reality ICPI describes permeable joint material as angular ASTM No. 8, 89 or 9 stone 1. Fairfax says to avoid sanding permeable pavement 2.
- Myth It never needs maintenance.
- Reality Fairfax and Howard both say to vacuum sweep at least twice a year, and ICPI says clogged surfaces can be restored by vacuuming 231.
- Myth It works on any soil.
- Reality ICPI uses partial-infiltration and no-infiltration designs where soils drain slowly or are weak 1. Low infiltration soils need underdrains or a liner.
The local variable: soil group, groundwater and frost
Three local facts decide the design. The soil’s infiltration rate decides whether water can drain into the ground or needs a pipe; ICPI says the site assessment should identify the NRCS hydrologic soil group, which sorts soils from A (water goes down) to D (high runoff) 1.
The depth to seasonal high water must be more than 2 ft under the base 1.
And cold-climate and freeze-thaw conditions raise frost questions that local engineers and your stormwater office answer 6. Our drainage research page covers soils and flooding.
When it makes sense, and your next step
Permeable pavers make sense when a city rewards or requires on-site infiltration, when the soil drains and the water table is deep, when the slope is gentle, and when someone will keep the surface vacuumed. They make little sense on a steep, clay, wet or dirty site, or where heavy trucks will park.
Your next step is to look at your lot’s drainage, ask your stormwater office what applies, and request a site assessment before pricing any system. If the answer is no, a standard paver base or a gravel surface may work better; compare the options if you are thinking of a walkway.
To find help, read the guide to choosing a landscaping company and ask each bid for the layer depths, the stone sizes and the maintenance plan in writing.
Questions about Permeable Pavers
What are permeable pavers?
Permeable pavers, or permeable interlocking concrete pavement, are concrete pavers laid with open joints filled with small stone over an open stone reservoir.
Rain passes through the joints, is stored in the stone and then soaks into the soil or drains through a pipe.
The pavers are not permeable themselves, says Fairfax County; the joints carry the water.
How do permeable pavers work?
Water moves through the stone-filled joints into open-graded stone layers below. ICPI says the system can infiltrate fully into the soil, partly with drain pipes, or not at all with a liner, depending on the soil. The stone layers hold water temporarily, support the pavers and help filter pollutants, according to Fairfax County.
Do permeable pavers clog?
Yes, with sediment. Howard County says trucks can grind dirt into the surface, leading to clogging and early failure.
Fairfax says to vacuum sweep at least twice a year, and treats water ponding in the observation well 72 hours after a half-inch storm as a clogging sign. ICPI says clogged surfaces can be restored with vacuum equipment.
What goes in the joints of permeable pavers?
Small angular stone, not ordinary jointing sand. ICPI Tech Spec 18 says permeable joint material typically consists of angular ASTM No. 8, 89 or 9 stone. Fairfax County lists sanding as something to avoid on permeable pavement, because sand can clog the openings that carry the water.
Can permeable pavers be used in freezing climates?
Sometimes, with local design. ICPI says the units resist freeze-thaw and deicing salts, and that installation can continue in cold weather if the subgrade and aggregates stay unfrozen. A CMHA summary says agencies and engineers had worried about heaving, freeze-thaw damage and blocked infiltration. Ask your stormwater office and an engineer about local frost.
Do permeable pavers work on clay soil?
They can, with a different design. ICPI says partial-infiltration designs, with perforated drain pipes, suit lower infiltration soils such as silts and clays, and that no-infiltration designs with a liner are required where soil has very low permeability or low strength. Plain full-infiltration designs suit sands and gravels.
How do you clean permeable pavers?
Vacuum sweep, at least twice a year, per Fairfax and Howard counties. Fairfax says not to sand, reseal, resurface or power wash, and Howard says washing systems and compressed air units should not be used. After sweeping, pour a five-gallon bucket of water on the surface to check that it soaks in.
How steep a slope can permeable pavers handle?
ICPI says the slope of the permeable surface should be less than 12% and is typically 5% or less. Steeper sites need terracing or another design.
The system also needs more than 2 feet between the base bottom and the seasonal high water table, and should sit down slope of building foundations that have piped footer drains.
Are permeable pavers allowed everywhere?
Rules are local. ICPI says its use is recognized by many stormwater agencies, and it recommends at least 100 feet from water supply wells with local rules possibly adding more. Some cities offer stormwater fee credits. Ask your stormwater or building office whether a permit, design standard or setback applies to your lot.
Sources
- Interlocking Concrete Pavement Institute, Tech Spec 18: Construction of Permeable Interlocking Concrete Pavement Systems (rev. March 2022; member-distributor PDF, text extracted with pdftotext), retrieved .
- Fairfax County Public Works and Environmental Services, Permeable Pavement fact sheet, retrieved .
- Howard County Department of Public Works, Bureau of Environmental Services, Permeable Paving: Operation and Maintenance (PDF, text extracted with pdftotext; created 2021-11-29 per file metadata), retrieved .
- U.S. EPA, Soak Up the Rain: Permeable Pavement (page marked no longer updated), retrieved .
- Interlocking Concrete Pavement Institute, Tech Spec 2: Construction of Interlocking Concrete Pavements (rev. February 2020; member-distributor PDF, text extracted with pdftotext), retrieved .
- Concrete Masonry & Hardscapes Association, Permeable Interlocking Concrete Pavement (PICP) Performance in Cold Climate, project summary PAV-FDN-003-13, retrieved .
Expert review
Written by the HyreYard Research Desk. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Layer sizes, site limits and design types are from ICPI Tech Spec 18, a trade-body bulletin, and are labeled as such. Maintenance rules are from two Maryland and Virginia county sheets and may differ elsewhere.
The EPA page is old and says it is not updated. The University of New Hampshire cold-climate study was not read; only a CMHA summary of why it was done.
Suggest a correction. We fix errors and say what changed.