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Mastering Hardscape Terminology

It is always a wise idea prior to meeting with your hardscape contractor to master a few key terms.  This will do two things: it will help you to understand what your visiting contractor is talking about, and help you to determine if your contractor even knows what they are talking about.  A sure-fire way to know if your contractor knows what he/she is doing is to find out if they even know the industry “lingo”.  Below we will cover some of the basic terminologies that may be discussed during your interview, or covered in your proposal.  We will discuss what they mean, and how they are important to the success of your project.

Hardscape – Hardscape refers to hard landscape materials in the built environment structures that are incorporated into a landscape. This can include paved areas, driveways, retaining walls, stairs, walkways, and any other landscaping made up of hard wearing materials such as wood, stone, concrete etc. as opposed to softscape, the horticultural elements of a landscape.

Geotextile – Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain. There are many different types of geotextile fabrics used for different purposes.  The two that you will want to remember are non-woven fabrics for permeable pavements and woven for standard pavers and driveway installations. Please be aware that weed barrier is technically a geotextile, but NOT of any grade that should be used in hardscape installation.  See the differences below.

Woven geotextile

Woven grid used primarily for retaining wall and paver base systems

Non-Woven geotextile

Non-Woven geotextile used primarily for permeable pavements, retaining wall applications, and water features.

Geogrid –  A geogrid is geosynthetic material used typically to reinforce soils and gravel materials. Geogrids are commonly used to reinforce retaining walls, as well as subbases or subsoils below roads or structures. While we usually use geogrids in reinforced retaining wall systems, we sometimes are able to use these grid systems in paver base installations in order to increase strength and decrease the base amount and client cost. There are two types of grids – Uniaxial, and Biaxial.  Using a biaxial grid eliminates a lot of human error as it is effective being installed in both directions while uniaxial is only effective in one direction.

Geogrid

Biaxial Geogrid used for strengthening paver bases, and aiding in global stability of soils and gravels behind retaining walls.

Densely-Graded Base – Densely-Graded base is a base in which the gradation, or the relative sizes of particles within the base, are highly variable and when lubricated with water will compact into a tight base which will bear a load. The gradation of a paver base is specific to its paver and function and is classified by an ASTM Standard.

Densely-Graded Base

A compacted Densely-Graded base installed as a paver base for a residential driveway.

 

Open-Graded Base – Open-Graded base is a base in which the gradation, or the relative sizes of particles within the base, are similar to each other. When installed as a base, it will bear a load and offer drainage as there is air space within the base. The gradation of a paver base is specific to its paver and function and is classified as an ASTM Standard.

Open-Graded Base

Installation of an Open-Graded base and setting bed on a residential permeable paver driveway

Angle of Repose – The angle of repose of granular material is the steepest angle of descent or dip relative to the horizontal.  This is important when assessing forces weighing against a retaining wall.  The greater the forces on a wall, the more consideration must be given to the design of the geogrid reinforcement behind the wall.

Angle of Repose

Graphic: ScienceDirect.com

ASTM Standards – ASTM stands for American Society for Testing and Materials and is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services.  This is important to you and your contractor as it establishes the exact grade of material that your paver or wall base is required to have.  Failure to install a base that is not within a certain ASTM standard for your application will ultimately lead to failure of your project.

ICPI – ICPI stands for Interlocking Concrete Pavement Institute. This organization leads the way with the training of hardscape contractors to install concrete paver systems.  They also conduct studies on the performance of pavement systems and write guidelines as to the installation of such systems. You can learn more about ICPI here.  It is imperative when speaking to any hardscape contractor that you are interviewing for your paver project, that you verify that they are certified through ICPI.

NCMA – NCMA stands for National Concrete Masonry Masonry Association. This organization leads the way with the training of hardscape contractors to install segmental retaining wall systems.  They also conduct studies on the performance of wall systems and write guidelines as to the installation of such systems. You can learn more about NCMA here.  It is imperative when speaking to any hardscape contractor that you are interviewing for your wall project, that you verify that they are certified through NCMA.

Standard Proctor Density – Standard Proctor density is the determination of the density of a material.  The Proctor compaction test is 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. Certified contractors know that certain types of base materials need to achieve a specific proctor density in order to be considered sufficiently compacted before moving on to the next step of the process. Not achieving adequate compaction will result in a failure of your pavement or wall system.

Proctor Density Test

Elegant Estates measuring the base density on a densely-graded base material on a residential paver driveway.

Permeable Paver Vs. Standard Paver – A permeable paver is a paver which is designed to allow water to go through the surface of the paver joints, while a standard paver required water to run off of the surface of the pavement.  While the pavers are indeed different, the difference is not so much in the paver itself, rather the manner in which it is installed. Since the two applications handle water differently, their entire systems are installed differently with different materials.

Standard Paver Detail

Permeable Paver Detail

Edge Restraint – An edge restraint is any type of material used to reinforce the edge of a paver to prevent migration of the pavers.  Typically this is a spiked poly material or poured concrete, but can also be curbing of various materials and styles.  Wood should never be used to restrain an edge as it will eventually rot and lead to a failed system.

Poly Edge Restraint System

The use of poly and spike edge restraints

 

Concrete Curbing used as an edge restraint

Concrete curbing was used on this driveway to act as an edge restraint.

 

Poured Concrete Edge restraint

The use of poured concrete as an edge restraint.

 

Soldier Course – Soldier course is a popular paver border in which the same sized pavers are placed side by side up and down the edge of your pavement project.

Sailor Course – Sailor course is a popular paver border in which the same sized pavers are placed end to end up and down the edge of your pavement project.

Inlay – An inlay is a design made out of pavers that are laid inside of the main field of pavers.  This breaks up the look of larger fields of pavers.

Paver Inlay

A strategic inlay breaks up this paver nicely.

 

Polymeric Sand – Polymeric sand is used to fill the joints between pavers, including concrete pavers, brick pavers, and stone pavers.  Some polymeric pavers are specifically designed for large gapped joints. This product is fine sand combined polymers that when mixed with water bind together. When dry, the polymeric sand acts like a hard mortar, and when wet, remain flexible.  This allows the pavement to flex as designed. Using anything other than polymeric sand for standard paver joints is not advised.

Poly Haze – Poly haze is a white haze that is left on the surface of your pavers from an improper installation by your contractor.  While water is required to activate the polymeric sand, too much water will wash out additional polymers which when left on the surface of your pavement will dry into a hazy appearance.

Paver Joint – A paver joint is the “crack” or space between your pavers.  It functions as drainage and stabilization for the paver system.  The joint fill will be different for standard versus permeable pavements.  While permeable pavers require fine drainable gravel, standard pavers require polymeric sand. Your paver joint plays a critical role in the overall interlock of your pavers.

Subgrade – A subgrade is referred to in a paver proposal often as the soil grade that exists under your paver base. It is important that your contractor understands the soil subgrade type so that the proper precautions can be taken to compact the base properly in standard applications and drain properly in permeable applications.

 

This glossary of terms will get you well on your way in understanding the hardscape verbiage used by your professional hardscape contractor.  When speaking to your contractor, be advised that if you know this terminology, and your contractor doesn’t, you may need to seek someone more proficient in the industry!

 

 

 

 

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