The first segmented roads were built by the Minoans about 5,000 years ago. The Romans built the first segmental interstate system, which was longer than the current U.S. Interstate Highway system. Most would agree that cobblestones offer an “Old World” beauty and charm, but the strength and The longevity of interlocking pavers is often overlooked in North America. This article will explain the basics of interlocking pavers and address common misconceptions about pavers.
It is important to understand that a paver installation is an engineered system; the pavers are simply one part of this system. The components of a paver installation, from bottom to top, are: compacted subgrade (or soil layer), geotextile fabric, compacted aggregate base, bed sand, edge restraint, pavers, and joint sand. Unlike cast-in-place concrete, interlocking pavers are a flexible pavement. It is this flexibility that allows the point load of a truck or car tire to be transferred and distributed through the base course to the subgrade. By the time the load reaches the subgrade, the load has spread over a large area and the subgrade is not deformed.
Concrete, on the other hand, is a rigid pavement. Its function is simply to join soft spots on the ground. Poured concrete will crack and break due to loads, shrinkage, soil expansion, and frost lift from the subgrade. Concrete is one of the most vital materials in construction, but poured-in-place concrete produces a poor paving surface. This is due to its relative inability to flex and its low tensile strength. Fiber reinforcement and rebar can improve the tensile strength of concrete, but cracking and breaking are inevitable.
Modular pavers are typically made of hardened precast concrete or kiln-fired clay. Properly installed pavers are interlocked, so the load on one paver is distributed among multiple pavers and ultimately transferred through the base course. Factors that affect interlock are paver thickness, paver shape, paver size, joint width, placement pattern, and edge constraint. Most paver manufacturers offer a lifetime warranty when their products are professionally installed. Natural stone such as Flagstone and Bluestone are not suitable for resilient paving and are typically set with mortar over a concrete slab. Because interlocking pavers are bonded with sand (rather than mortar), they can be cheaply lifted and replaced. For example, pavers can be raised to access underground utilities and reset when the job is complete.
Paving system designs are based on variables including soil composition, anticipated load stress, weather, water table, and rainfall. The materials used for the aggregate base and bedding sand vary geographically. Soils that have a high clay and marl content are not suitable for compaction and cannot be used as base material; in these cases it is replaced by graduated crushed stone. Proper compaction of the subgrade and base material is critical to the long-term performance of a paving system, and in vehicular applications, the depth of compacted base can exceed 12 inches. The edges of a paver installation must be restrained to ensure interlock and prevent side slippage. The most common types of curb restraint are the plastic staked curb restraint, precast concrete curb, and cast-in-place concrete. Bedding sand materials include angular sand, manufactured sand, and polymeric sand.
The beauty and longevity of a paver system is determined by its designer and installer. Properly installed pavers offer a lifetime paving solution. Improperly installed pavers can fail in a matter of years. When choosing an installer, look for training, experience and references.
Frequent questions
Q: Are the pavers pervious (or pervious)?
A: Most paver installations are waterproof (waterproof). However, most manufacturers offer pervious pavers, which are installed on an open base. A pervious system is designed to store water in the base material so that it can be released back into the soil. These systems reduce runoff, recharge groundwater, and eliminate the need for detention ponds.
Q: Can pavers be installed on a steep slope?
A: Yes, pavers work great on steep slopes, but joint erosion can occur in heavy rain. In these cases, polymers are added to the joint sand to prevent sand washing.
Q: Do pavers settle over time?
A: Settlement is almost never a problem with properly installed pavers. However, soft areas in the subgrade must be addressed prior to base placement. Trash pits and decaying organic material should be removed and replaced with compacted base material.
Q: Can pavers be used for roads?
A: Paving systems can handle tremendous loads and for this reason they are often used at airports and seaports. However, pavers are not suitable for high speed vehicle traffic and braking forces.
Q: Will pavers help my drainage problems?
A: Water management is addressed during the design phase. When there is very little slope or a negative slope, surface drainage; channel drains; and drain lines are used to direct water away from structures.
Q: Will weeds grow in the joints?
A: Airborne weeds can take root in bed sand, but they are easily controlled with herbicides. Polymeric Joint Sand can be used to prevent weed growth and stabilize joints.
Q: Where can I find a good installer?