Edgewater Ferry Terminal Canopy, Edgewater, NJ (Fabritec Structures)

The hardest part of designing and building a fabric structure is determining its cost. There are 3 major components to a fabric structure (steel, fabric and connections) and every decision made on the design and its install affects the cost as well. The more complex and steel there is on a project, the more it will cost to fabricate and install. The fabric and hardware chosen is just as important as the paint finish and the foundations. Location, site access and labor rates also play a major role.

My advice? Keep it simple.

Fabric Structures are mostly used as a cost effective solution to providing shade and shelter. The added bonus is that it is festive in nature and can be used for temporary or permanent applications. The beauty of these structures is in the details so keep them simple.

THE DETAILS

One’s signature or style is often expressed in the details of a project.  Detailing fabric structures is no different.  Architects, designers, consulting engineers and clients all have different ideas on how a fabric structure and its details should look. The designer must take into account the different demands required for the details during the life of a fabric structure and subsequent cost.  Issues to consider are the following:

Economics
The cost of designing custom components needs to be weighed against the use of semi-finished products (i.e. tube, pipe, etc.) and fabricated parts (bolts, nuts, shackles, etc.). Selecting the method by which primary components are made can greatly influence the overall cost of a structure.  A minimum number of elements are usually desirable. Membranes have different cost as well. There are some membranes with longer life spans than others and their selection should be based on application and life span.
.
Material
The different material properties (strength, thickness, elasticity, weight, etc.) make material selection critical.  For example, use of high tensile materials with smaller cross sections most often implies higher material cost.  However, using low strength materials with larger cross sections increases the weight and cost of the installation.  A need for components to be highly abrasion-resistant, low maintenance and “vandal proof” also influences the choice of suitable materials. Memembranes come with different "top coats" which provide different forms of protection. Again, their selection should be based on their application and life span.

Production
Various production processes (welding, forging, casting, etc.) have their own advantages and disadvantages that dictate the design of structural components.  In addition, the quantity of parts required (single vs. mass production), play a significant role in determining whether a custom component is feasible and cost effective.  For membranes, symmetry and optimization of cutting patterns is important. The fewer the number of cutting patterns, the more cost effective the production with be. Lastly, the ability to transport components to the job site must be considered.

Long Branch Sails, Long Branch, NJ (FabriTec Structures)

Anatomy of a Fabric Structure

The best way to understand the cost of a fabric structure is to request a Schedule of Value (SOV) or a breakdown of the major cost (design/engineering/project management, steel, fabric and hardware fabrication, installation and equipment and shipping). The percentage of the overall cost can vary significantly depending on the complexity of the design, the material chosen, the location and access of the site, the cost of labor and equipment and the amount of material needed to be shipped. Keep in mind, Fabric Structures are normally priced by surface area because of their unique shapes.

Here is a basic rule of thumb:

Plan Area (Length x Width) X Shape Factor (H) = Surface Area

Shape Factor is a number which varies depending on the form chosen and is used to estimate the amount of fabric including waste used on a proejct. Mast supported structures tend to have twice as much material as a hypar and barrel vault design.

Surface Area X Cost per SQFT= Budget

Schedule of Values (SOV)

Price per Square foot of common fabric structure materials (2012) based on a min. surface area of 5,000 sqft (500 sqm).

Please note, there is a large variable in cost per square foot because the more steel you use on a structure (frame supported vs a mast supported), the more expensive it will be. Also, there are many "grades" of PTFE, PVC and HDPE.

The key is to design the lightest structure possible. Less is more. Light is even better.