Stone Pavement

 

 

 

 

 

 

 

 

 

Stone is a versatile and durable natural paving material commonly used in landscape construction. With a variety of different applications, stone can be featured as a naturalistic or architectural element in a pavement pattern, and its natural color and texture variations can add considerable visual interest. Stone comes in a wide range of types and colors depending on the natural mineral content of the quarry it is mined from, so landscape designers have plenty of options from which to choose.

Stone pavement can be broadly categorized as either dressed or rough/naturalistic. Dressed stone refers to pieces which have been cut to a regular shape or dimension (i.e. Bluestone pavers), whereas natural stone retains its naturally occurring shape or dimension (flagstone, inset cobbles, etc.)

 

PROS & CONS

Advantages:

-Because stone pavement is composed of modular pieces arranged to cover a given area, the installer has some control over where surface jointing will occur.

-Jointing can be a naturalistic/irregular pattern, or a geometric pattern, depending on the desired aesthetic and the type of stone selected. The designer has considerable influence over how the finished pavement will look.

-Most stone pavement types are very durable

-A very decorative, premium finish material

 

Disadvantages:

-Depending on the application, a concrete base slab may be required to support the surface pavement, adding considerable site preparation work and material requirements.

-Although there is some degree of control over where the jointing occurs, stone pavement may require a bond breaker if placed on a concrete slab, to avoid surface cracks appearing above joints in the slab below.

-As a premium finish material, stone is often considerably more expensive to install than concrete or asphalt pavement.

 

CONSTRUCTION

The sequence of construction is usually as follows:

EXCAVATION/GRADING

As a first step, the area to be paved will be excavated to allow for a proper building surface to be constructed beneath the pavement. Depending on the pavement’s intended use, the depth and bearing capacity of the base material will vary. Stone pavement designed to receive vehicle traffic (“heavy duty”) will usually require at least an 8” concrete slab below the pavement, with a 12” aggregate base below that. A pedestrian-only surface can be installed on as little as 8” below of crushed stone if the ground below is sufficiently compacted. If you are unsure, a landscape architect or civil engineer can make a recommendation for your project taking into account specific attributes of your site.

Once the excavation is completed to attain the necessary depth, the exposed earth surface below is compacted, usually to a minimum of 95% Proctor Density, or an engineer’s recommendations.

AGGREGATE BASE

Once grading and subgrade preparation is complete, a base course will be laid to provide a stable platform for the pavement profile above to rest on. In most cases, a dense-graded aggregate will be used, since the range of particle sizes can lock together to form a very supportive aggregate base. For applications with permeable joints between stone pavers, an open-graded aggregate or crushed stone will be specified instead, to allow for free drainage below the pavement. The base is distributed over the compacted subgrade in the area to be paved, and is then mechanically compacted itself, either by a steamroller or manual vibrating plate compactor (for smaller areas).

Once the base course is in place, the pavement can be installed.

POUR CONCRETE (IF NEEDED)

If stone pavement is to be placed on a concrete slab, the formwork for the base slab should be constructed to create a container in the desired shape. Some applications may call for a reinforced concrete base, which will require that rebar or welded wire mesh be installed before pouring the concrete. Then, the concrete should be poured into the form(s) to achieve the desired thickness above the aggregate base. Expansion and contraction joints should be installed with the pouring of the concrete base slab, and a bond breaker (usually construction felt) should be provided for in case it is needed later to prevent cracking. Usually expansion joints in the base slab should be no greater than 30’ apart. As this concrete is not the finished pavement surface, it does not require any particular type of finish, although a rougher surface may help give the mortar more to adhere to when the stone is installed above.

INSTALL STONE PAVEMENT

Stone pavement can now be mortared to the concrete base slab, or placed directly on the compacted stone base. If unsure what your pattern will look like and want to test it out, the stone can be laid out on the prepared base material with no mortar and field adjustments can be made to be sure it looks as intended.

When installing stone pavement, mortar should be applied to the concrete base, with the stone then being set into the mortar bed. Mortar should then be added to fill in the joints between the stones, using the appropriate masonry tools to clean up any excess along the way.

Some common pattern types for stone paving include:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Many designers find creative ways to use and combine these patterns as the site design calls for. More formal garden layouts or styles may be more suited to the geometric stones of an ashlar or bond pattern, while informal or flowing “gardenesque” style may demand irregular stones or patterns. These styles can also coexist within the same design, and transition spaces may be an opportunity to provide cues that reflect this shift of attitude with the pavement itself.