paving material

Permeable paving

Permeable paving, is different than pervious paving or porous pavement, by virtue of the fact that rainwater passes around the paver as opposed to passing through the paver helping to reduce or eliminate "clogging" found in pervious or porous systems. "Permeable" is a term used to describe paving methods for roads, parking lots and walkways that allow the movement of water and air around the paving material. Although some porous paving materials appear nearly indistinguishable from nonporous materials, their environmental effects are qualitatively different. Whether porous asphalt, concrete, paving stones or bricks, all these pervious materials allow precipitation to percolate through areas that would traditionally be impervious and instead infiltrates the stormwater through to the soil below. The infiltration capacity of the native soil is a key design consideration for determining the depth of base rock for stormwater storage or for whether an underdrain system is needed.

In new suburban growth, porous pavements protect pristine watersheds. In areas already built out, old town centers, redevelopment and reconstruction are opportunities for environmental rehabilitation. Permable paving is an important component in low impact development, a process for land development in the United States that attempts to minimize impacts on water quality.

Advantages of permeable paving

Permeable paving surfaces are highly desirable because of the problems associated with water runoff from paved surfaces. Part of the problem is creating an unnatural volume of runoff from precipitation, which causes serious erosion and siltation in streams and other bodies of waters. Part of the problem is also the washing off of vehicular pollutants into water bodies.



However, permeable pavements require frequent maintenance because grit or gravel can block the open pores. This is commonly done by industrial vacuums that suck up all the sediment. If maintenance is not carried out on a regular basis, the porous pavements can begin to hold large amounts of water and cause flooding. With more advanced paving systems the levels of maintenance needed can be greatly decreased, concrete block permeable paving requires no more maintenance than regular concrete paving as the grit between the blocks enhances the filtering properties of the pavement. Also, in a large storm event, the water table below the porous pavement can rise to a higher level preventing the precipitation from being absorbed into the ground. The best way to prevent these problem is to allow for adequate rain water run off at the pavement design stage.

Disadvantages of permeable paving

There are good New alternatives for example the Sustainable urban drainage systems system. The benefit of these pavers is that they don't severely lose their colour over time or get clogged pores that eventually prevent the bricks from absorbing water.

The Limitations of Permeable Paving,

Run off Volumes

Permeable pavements are designed to replace Effective Impervious Areas (EIAs), not to manage storm water from other impervious surfaces on site. Use of this technique must be part of an overall on site management system for storm water, and is not a replacement for other techniques.

Pollutant Load

Highly contaminated runoff can be generated by some land uses where pollutant concentrations exceed those typically found in storm water. These "hot spots" include commercial nurseries, recycling facilities, fueling stations, industrial storage, marinas, some outdoor loading facilities, public works yards, hazardous materials generators (if containers are exposed to rainfall), vehicle service and maintenance areas, and vehicle and equipment washing and steam cleaning facilities. Since porous pavement is an infiltration practice, it should not be applied at storm water hot spots due to the potential for ground water contamination. All contaminated runoff should be prevented from entering municipal storm drain systems by using best management practices for the specific industry or activity.CRD Watershed Best Practices

Weight & Traffic Volumes







Some estimates put the cost of permeable paving at two to three times that of conventional asphalt paving. Using permeable paving, however, can reduce the cost of providing larger or more storm water BMP’s on site and these savings should be factored into any cost analysis. In addition, the off-site environmental impact costs of not reducing on-site storm water volumes and pollution have historically been ignored or assigned to other groups (local government parks, public works and environmental restoration budgets, fisheries losses, etc.) The City of Olympia in Washington State is studying the use of porous concrete quite closely and finding that new storm water regulations are making it a viable alternative to storm water ponds.


Some permeable paving products are prone to damage from misuse, such as drivers who tear up patches of plastic & gravel grid systems by “joy riding” on remote parking lots at night. The damage is not difficult to repair but can look unsightly in the meantime. Grass pavers require supplemental watering in the first year to establish the vegetation, otherwise they may need to be re-seeded. Regional climate also means that most grass applications will go dormant during the dry season. While brown vegetation is only a matter of aesthetics, it can influence public support for this type of permeable paving. Olympia, Washington has found that porous concrete mix quality can be difficult to control , as it is sensitive to water and difficult to blend correctly. As well, few local contractors know correct installation techniques. The city is still working on how, and how often, to clean porous concrete. Olympia expects to solve these problems as it gains more experience.


So what exactly is Efflorescence?


The problem with Efflorescence


The solution to removing Efflorescence

Efflorescence Removers effectively removes the calcium/lime build up without damaging the integrity of the surface it is cleaning unlike more harmful cleaners such as muriatic acid. Efflorescence Removers is an environmentally safe, non toxic alternative that will not harm plants or animals and does not discharge any offensive odor, making it the ideal cleaner for application in public areas. Efflorescence Removers should be applied by hand pump sprayer to the surface until foam begins to appear. The foam only appears when efflorescence is present. Wait five minutes, mechanically agitate and wash. Re-apply to areas where the foam appears and continue to reapply until the foam no longer occurs after application. One gallon of Efflorescence Remover covers 350 square feet.

Types of permeable paving surfaces

Installation of porous pavements is not more difficult than that of dense pavements, but it is different, and its different specifications and procedures must be strictly adhered to. Nine different families of porous paving materials present distinctive advantages and disadvantages for specific applications. Here are examples:

"Porous asphalt" is mixed at conventional asphalt plants, but fine (small) aggregate is omitted from the mixture. The remaining large, single-sized aggregate particles leave open voids that give the material its porosity and permeability. Under the porous asphalt surface is a base course of further single-sized aggregate. Porous asphalt surfaces are being used on highways to improve driving safety by removing water from the surface.

"Porous concrete", like porous asphalt, can bear frequent traffic, and is universally accessible. Its quality depends on the installer's knowledge and experience.

"Single-sized aggregate" without any binder is the most permeable paving material in existence — and the least expensive. Although it can be used only in very low-traffic settings such as seldom-used parking stalls, its potential cumulative area is great.

"Porous turf", if properly constructed, can be used for occasional parking like that at churches and stadiums. Living turf transpires water, actively counteracting the “heat island” with what appears to be a green open lawn.

"Open-jointed blocks" are concrete or stone units with open, permeable spaces between the units. They give an architectural appearance, and can bear surprisingly heavy traffic, particularly interlocking paving blocks.

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