Best practices for installing interlocking concrete pavers

by jason_cramp | April 1, 2015 2:10 pm

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By Brian Burton

Author’s note: There are profitable long-term opportunities for pool and spa contractors in the maturing markets for interlocking concrete pavers (ICPs). In addition to excellent appearance and durability, ICPs offer a host of attractive landscaping possibilities as a result of the vast range of colours, textures, and shapes that are available. This article is the first of a series which will provide readers information on these innovative pavements, outline proper installation techniques, as well as appropriate methods to maintain and repair these hardscaping systems.

Interlocking concrete pavers (ICPs) are typically constructed as ‘flexible’ pavements on a well compacted soil subgrade and compacted aggregate base. Hand-sized concrete paver units are then placed on top of the base on a thin layer of bedding sand. The pavers are then compacted; sand is swept into the joints, and compacted again. When compacted, the pavers interlock to create a ‘flexible’ forgiving pavement system, which transfers vertical loads from vehicles to surrounding pavers by shear force through the joint sand. The sand in the joints enables applied loads to be spread over a wide area reducing the stresses on the base and subgrade.

ICPs, as they are known today, were developed in Europe in the ’50s as a replacement for clay bricks which were, up until that time, typically used to pave most streets. The long-established tradition in Europe resulted in tremendous growth in the North American industry and quickly established pavers with design professionals and consumers. In fact, more than 50,000 ha (123,553 acres) are installed annually around the world.

Indeed, many ICP installations today are nothing short of spectacular. The long-standing perception of this hardscaping material as being ‘bland’ has been replaced by a new bolder vision. The wide range of shapes, colours, and surface textures now available are revolutionizing the entire scope of hardscaping design and installation.

Bring the client’s landscaping up to speed

In the past, most backyards tended to be a haphazard affair with no overall design strategy. Today, however, most homeowners regard their backyard landscaping and pool and spa/hot tub amenities as extensions of their indoor living space. In many instances, these backyard spaces are designed and built to make a unique statement. However, proper paver installation requires skill, experience, and attention to detail on the part of the contractor to achieve the desired effect the homeowner is looking for, while contractors need to develop workable designs and cost-effective installation plans.

When developing and preparing a hardscaping proposal, keep the following in mind:

• Inspect the property thoroughly from all angles and discuss the homeowner’s lifestyle as well as his/her plans for the property; and
• Make a habit of developing a ‘conceptual’ approach to the design in draft form, which can be used to ‘firm up’ the quote. When possible, make a formal presentation of the finished proposal to the client.

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Selecting paving stones

Understanding how ICP systems function is an important part of proper installation. When planning the installation, the overall environment and the strength of the underlying soil subgrade should be considered.

ICPs can last 40 to 50 years and because of this it adds a sizeable amount of value to the client’s home. Further, they also allow the homeowner to co-ordinate and customize activity space, including driveways, walkways, patios, pool decks, and gardens in a way that was never before possible.

The number of consumers selecting ICPs for residential applications has grown rapidly. There are an increasing number of published reports by experts which rate ICPs as the best value for the money by a considerable margin over traditional pavements. In fact, many consumers learn the surprising truth about their landscaping when they put their home up for sale. Further, when landscaping elements are properly installed and maintained, they have a significant long-term influence on the market value of the property.

Base basics

A compacted aggregate base is essential to the proper installation of ICPs. Some of the most common questions and answers with regards to installing this base include:

Q. What is the base?
A.The base is made from stone crushed at a quarry and generally ranges in size from 19 mm (0.75 in.) to very small particles called ‘fines.’ It is graded or sorted after crushing by placing it on screens of different sizes mixed together in various proportions to create a range of particle sizes. The range creates a dense material when compacted.

Q. What is the right mix of particle sizes?
A.Crushed rock normally used under asphalt driveways and roads is generally acceptable under concrete pavers and bedding sand. The mix of particle sizes is often set by provincial or city standards. These materials can be used under patios, driveways, and streets. For example, granular ‘A’ base is commonly used in Ontario.

Q. Where is the base placed?
A.The compacted aggregate base is placed on top of the compacted soil subgrade.

Q. How much base should be used?
A.For patios and walkways, a minimum compacted thickness of 100 to 150 mm (4 to 6 in.) should be used, while for driveways the minimum compacted thickness is 150 to 200 mm (6 to 7.8 in.).

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Q. How is it installed?
A.The aggregate base should be installed in compacted layers of approximately 50 to 75 mm (2 to 3 in.).

Q. What type of equipment is required to compact aggregate base material?
A.For patios and walkways, a five‑horsepower (hp) plate compactor will do the job. The plate compactor should have at least 18 to 22 kN centrifugal force (4046 to 4945 pound force [lbf]). For driveways, a large, high-frequency plate rammer or vibratory roller can be used. A walk-behind or ride‑on roller can also be used.

Q. What about maintaining the slope or grade for drainage?
A.Slope the base away from buildings for drainage to remove rain and snow. Walkways and driveways should also slope to remove water. Maintain a slope while keeping a consistent thickness throughout the base by using string lines tied to stakes. Set the lines to mark the final grade. Check depth measurements along the string lines when excavating the pavers.

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Edge restraints

Edge restraints hold ICPs firmly in place and resist the forces of traffic or minor settlement. They also serve an important function in holding bedding sand in place and preventing its migration.

Edge restraints are vital components and are essential for trouble-free performance. When a compacted aggregate base supports the pavers and bedding sand, the base should extend beyond the restraint. As a rule of thumb, the base should extend beyond the restraint the same distance as the thickness of the base material. For instance, if the base is 150-mm (6-in.) thick then it should extend at least 150 mm (6 in.) beyond the outside edge of the restraints. This adds stability to the restraint, especially in soils subject to heaving.

There are two general types of edge restraints. The first type includes products manufactured from plastic, precast concrete, cut stone, aluminum, steel, and timber. The second type is formed on-site and comprises poured-in-place concrete.

Manufactured edge restraints

Plastic edging will not rust or rot and provides a rigid structure when spiked in place (using steel spikes), as well as contributing flexibility when the pavement is subject to freeze-thaw, moisture, and loading. Plastic restraint systems can be cut quickly with a hacksaw and can be used with light-duty residential, commercial, or, depending on the design, in some heavy-duty industrial applications.

Aluminum and steel edging provides a smooth vertical surface against the pavers. Steel should be painted or galvanized so rust does not stain the pavers. Spikes to secure steel and aluminum edging should extend well into the base course. Consult manufacturer’s literature for the recommended spacing of the spikes. Aluminum and steel edging are manufactured in different thicknesses. The thickest edging is recommended when pavers are subjected to vehicular traffic.

Full-depth precast concrete or cut-stone edging can be set in compacted aggregate or concrete backfill. For pavements exposed to vehicular traffic, the preferred method of installation is for the curb to rest on the compacted aggregate. Partial-depth precast concrete edge restraints may be used for residential and light-duty commercial applications. These precast units are anchored on a compacted aggregate base with steel spikes.

Construction tips
When the gap between the pavers and the edge restraint exceeds 10 mm (0.39 in.), the space should be filled with a cut paver. A clean appearance is possible when a running course is placed parallel to a straight, flush edge. This detail can reduce incidental chipping of cut pavers.

Edge restrains formed on site

Poured-in-place concrete curbs or combination curb and gutters make suitable restraints for pavers.  Exposed concrete edges should have a 3-mm (0.12-in.) radius edge to reduce the chance of chipping. As with precast edge restraints, the side of the curb should extend well below the sand bedding course.

Other edge restraint considerations

Pay careful attention when compacting pavers along the edge of the restraint material. Over time, settlement can occur if the pavers are not compacted properly. Using a plate compactor and a little extra care around these areas can ensure a quality installation.

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Essential design elements

When designing hardscaping installations consider the following elements when preparing a client quotation:

• The main entrance of the residence will be the primary focal point and the treatment of this area often sets the tone for the entire landscaping design. In some cases, the property owner may indicate otherwise for reasons of privacy or security.
• When developing a design approach, contractors should consider the vantage point. As a rule of thumb, paving installations, when properly designed, should ‘welcome the way’ for guests.
• Effective hardscaping works most effectively when co‑ordinated with the scale of the property. This can mean emphasizing certain attributes or spaces that make the property standout from its neighbours.
• Wherever practical, landscaping should echo or reinforce the architectural style of the property.
• Ensure dominant colours displayed in the façade and plants surrounding the home are co-ordinated effectively with the hardscaping. Also keep in mind, minor differences in texture can be magnified in landscaping.
• There are occasions when rapid changes in grade or water features, such as pools and ponds, should be considered during the design stage.

Pavers improve safety

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Special surface finishes such as shot blasting, tumbling, and bush hammering can be produced to provide an upscale architectural appearance. They are manufactured from Portland cement and fine and coarse aggregates. Pigments are added as a colouring agent along with chemicals to repel moisture, improve strength, and increase durability.

The ingredients are mixed with a small amount of water and moulded under vibration and extreme pressure to create a consistent and durable segmental block unit. Most blocks have a chamfer (shallow angled cut) around the top edge to improve pedestrian comfort and safety. The chamfer also improves the appearance of the blocks, minimizes damage during installation, and facilitates drainage. The units commonly incorporate protruding placement ribs on their sides to maintain a uniform 2-mm (0.08-in.) space around the installed units. Special surface finishes are created using unique aggregates, colour, polishing, and other techniques.

A hard-wearing surface

ICPs are manufactured of materials with an exceptionally long lifespan. There are many examples of ICPs in continuous use for more than 40 years. Unlike some other traditional surfaces, concrete blocks are structurally resistant to frost damage, most chemicals, fuel, and oils, making them suitable for use in demanding applications. The durability of ICPs also means they require very little maintenance.

Common installation deficiencies

• Failure to compact to 95 per cent proctor density (a laboratory method of experimentally determining the optimal moisture content at which a given soil type will become most dense and achieve its maximum dry density). • Failure to install edge restraints at perimeter of pavement. • Failure to the properly specify and install base and sub-base materials. • Failure to adequately re-compact the pavement system after the installation of joint sand.

Where loads are applied to ICPs their interlocking action dissipates the pressure sideways and downwards into the sub-base. Similarly, should the underlying materials move, the blocks are flexible enough to follow the line of settlement without failing. This flexibility, coupled with high strengths, makes the units suitable for pool and spa deck applications.

Routine visual inspection

It is a recommended practice to conduct an annual visual inspection of ICPs in the spring to identify any units that may have been damaged or displaced. (Unlike conventional pavements, stained, or damaged ICPs can be replaced.) The joints between the pavers should be inspected to determine if any sand has been lost. Joints with low or no sand should be topped up with bedding sand and swept clean. Cleaning and sealing will discourage ants and weeds in the joints and enhance the colour of the surface. It is a great way to add new life to a refurbished area.

[7]Brian Burton operates a multidisciplinary firm that specializes in website design and development, and technical business writing. The firm also assists companies interested in selling goods and services to governments and institutions. He can be reached via e-mail at burton@award-bid-management.com[8].

Source URL: https://www.poolspamarketing.com/trade/best-practices-for-installing-interlocking-concrete-pavers/

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