Choosing the Right Building Stone

Table of Contents

Considering that stones are exposed to wear and impact, they must possess the following characteristics:

Factors Influencing the Choice of Building Stone

Color of Stones

Durability of Stone

Stone Texture

Mineralogical Composition of Stone

Choosing the Right Building Stone

Today, due to advancements in extraction and transportation technology, the use of stone has expanded significantly, finding application in various construction sectors. Choosing the right building stone that is highly compatible with the environmental climate to ensure the durability of the structure is a crucial point that buyers must take into consideration.

If you intend to purchase stone—such as travertine, crystal stone (marble), marble (مرمریت), etc.—for your building, you must select the type based on the specific area of the building where the stone will be installed. Typically, spaces are categorized into the following groups:

Exterior facade
Interior facade
Stair treads and landings
Flooring for residential interior spaces
Flooring for commercial and office interior spaces
Rooftop and sidewalk flooring
Restrooms and bathrooms
Wall caps for boundary walls, yards, and roof parapets
Kitchen countertops and islands

Considering that stones are exposed to wear and impact, they must possess the following characteristics:

Low porosity
Aesthetic appeal in color and appearance
Washability and resistance against acids, bases, and detergents
The capability to be cut in one direction (a characteristic found in metamorphic stones and some sedimentary rocks).
High strength and hardness.
Relatively high abrasion resistance.
High impact resistance.

The best stones for flooring and staircases are gneiss and quartzite.

Interior Wall Cladding

Most interior walls of office buildings, public and sanitary facilities, retail stores, and dining halls are covered with stone. The stones used for this purpose must possess the following features:

Optimum polishability
Low porosity
Aesthetic color and appearance
Washability and durability against detergents

Building Stone Facade

The most frequent application of stone in construction is for facades. Building facades are constantly exposed to weather conditions such as rain, frost, sunlight, and pollutants; therefore, facade stone must possess specific characteristics to withstand these factors. Consequently, special attention must be paid to the following points when selecting stone for a building facade:

Its mineralogical composition must be considered, as harmful minerals (iron minerals) oxidize in weathering conditions and cause stone degradation.
It is better to choose the facade stone in proportion to the expected useful lifespan of the building.
The stone should be selected according to the region's climate and weather conditions. For example, in cold and humid areas, the stone must have very low porosity; otherwise, it may disintegrate due to successive freezes. In locations prone to sandstorms where the stone is exposed to friction, an abrasion-resistant stone must be chosen.
The selected stone must have good polishability and cutting capability.
If installed using the wet method, it must exhibit good adhesion to the mortar.
Its color must be stable.
It should be resistant against vapors, gases, and sunlight.
It should have relatively good tensile and flexural strength.

Factors Influencing the Choice of Building Stone

At the beginning of the project, the intended application must be specified, and these factors should be determined accordingly. Overall, the key factors in choosing the right building stone include price, color, durability, and technical specifications.

Color of Stones

This factor is primarily important from an architect's perspective, although engineers also weigh in on stone color. Light colors are generally preferred over dark ones. This is particularly significant in limestones because most dark-colored limestones cannot withstand sunlight and air pollution in exterior building facades. The color green is a trait of great economic importance. Stones with rare colors such as green, azure, and red hold higher value. Sometimes viewing distance matters in perceiving stone color. A medium-grained granite containing pink feldspars will not display this feature from a distance; likewise, a multi-colored piece of it will appear monochrome from afar. Therefore, whether a stone is monochrome or multi-colored should be evaluated at a distance of about 20 to 50 centimeters from the eye.

Durability of Stone

The durability of a building stone refers to its resistance against chemical attacks and weathering agents. Unfortunately, stone durability—which should be the most important factor in stone selection—is frequently overlooked. There are many expensive buildings where this issue was disregarded during stone selection, resulting in financial loss. Natural factors influencing this include structure, texture, and mineralogical composition. The installation location of the stone within the building and its application are other factors affecting stone durability. Additionally, climate conditions are extremely important; chemical weathering is more dominant in hot and humid climates, while physical weathering is more prominent in cold and dry climates.

Stone Texture

Stones may feature uniform coarse-grained or fine-grained crystals, or a porphyritic texture (unequal crystals). Coarse-grained stones fracture sooner than fine-grained ones and are particularly sensitive to temperature changes. This type of failure is at least partially related to the differences in the expansion coefficients of the minerals making up the stone. Stones can also be dense or porous. Dense stones disintegrate slower than porous ones. Dense stones are nearly impermeable, so weathering agents cannot act rapidly. On the other hand, stones with open and capillary porosity easily absorb water and suffer from cracking due to frost.

Mineralogical Composition of Stone

Since various minerals exhibit different resistances against the attack of weathering agents, it is natural that stones possess varying resistance to weathering due to their distinct constituent minerals. Those containing minerals with lower resistance will sustain damage sooner from various factors.