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Estimating the Cost of Building Fire Sprinkler Systems

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Fire sprinklers are becoming a requirement in many city and state codes for new buildings and remodels.
(Excerpted from the Newly Revised Standard Estimating Practice, Ninth Edition)


In the typical construction drawing phase, the building interior sprinkler is in a “design drawing condition”. After the general contractor receives its notice to proceed, and often after the project has received its permit to construct, the Sprinkler Installer/designer and special systems suppression designer will then submit stamped design drawings for approval.
The estimator can, however, expect complete construction drawing information for fire undergrounds, fire hydrants, and required FDCs. Specifications should indicate the required sprinkler spacing and type of sprinkler heads but not necessarily the completed design drawings for the interior system. The construction estimator should fully review all of the plans and specifications and perform a site walk.  Due to the construction drawings being incomplete regarding the interior system, any introduction to fire sprinklers and fire suppression systems requires exposure to NFPA codes. These codes must be understood to estimate the sprinkler system. The National Fire Protection Association (NFPA) manual is the primary design reference.

An important NFPA abbreviation is the Authority Having Jurisdiction, commonly referred to as “AHJ”. The AHJ is the designated authority for interpreting and applying the appropriate NFPA and local codes for each project. The AHJ, Owner specifications and Architect/Engineer specify the system and codes required for that location. The AHJ is typically the State, Local or University Fire Marshal, or State building official. The Architect/Engineer develops the contract documents based upon the codes and any requirements of the owner -- including the owner’s insurer specifying the requirements of Fire Sprinkler design – but, many times, not actually designing it. It is important to understand these requirements and any requirements of the owner’s insurer.  For example, Factory Mutual and the owner may require Schedule 40 seamless pipe rather than the lower cost Schedule 10 pipe, and closer sprinkler spacing than NFPA standards, for example.

Measurement Methods
Quantity takeoffs in fire suppression construction measure multiple components, including undergrounds for fire mains and site fire hydrants, as well as the building interior and specialty fire suppression systems.  When estimating underground site fire piping, the NFPA may need to be referenced if the construction documents do not include the fire pipe burial depths.

Once accurate lengths, depths, and widths are determined, these three dimensions can be used to calculate excavated trench volumes, pipe bedding and backfill. The construction estimator will utilize the correct conversion factor from CUB YD to TON to determine the quantities of pipe bedding required.

It may be necessary for the construction estimator to factor waste into the calculations. Trench spoils will swell per bank compaction excavation calculations. The actual volume of material to be handled is the “bank” yardage, as measured from the plans. Backfill will sometimes leave spoils that will need to be graded into the site or removed from the site if cobble and stone are encountered. Shrinkage of backfill may occur, depending on the material placed, if it is compacted better than bank ratios, and is also subject to spillage loss as material is handled repeatedly.

Piping is measured in lineal feet and can be calculated as follows:

  •  Beginning with the largest size or the point of origin for a system of piping, measure all horizontal piping from the floor plan.
  •  Count the drops, risers and stacks, and multiply them by footages derived from elevations, sections, and cut sheets.
  •  Count tees, then elbows, then valves.
  •  Add adapters and flanges needed to connect piping to fixtures and equipment.
  •  Calculate quantities of hangers and supports needed for all piping – hangers for horizontal pipe and riser clamps for vertical pipe.
  •  Include pipe markers, valve tags, and equipment labels.
  •  Clearly mark or color items that have been taken off and recorded. If an item is not colored or marked, assume that it has not been taken off.

Sprinkler Piping is typically sold in 20’ lengths and field cut. Larger sizes may be transported in shorter 10’ lengths, due to the onsite handling weight of the larger diameter piping. 20’ pipe is field cut and threads must be field cut into the ends. In pipe sizes 3” and under, the cost of cutting threads into the pipe must be added to each end -- but typically 3” pipe diameter and larger uses Victaulic compression fittings with no threading labor cost required. Fittings, such as nipples, tees, elbows, reducers, escutcheons, and sprinkler heads require a quantity take off based upon the anticipated pipe routing and sprinkler head locations.

Project-Specific Factors in Takeoff and Pricing
Suggested method for organizing the estimate:


1) Site: Underground Fire main to the building and Fire Hydrants.
2) Building Sprinklers and their required risers and equipment.
3) Additional potential cost items.

1) – Site: Underground Fire Main to the Building and Fire Hydrants
The typical contract documents for a major site will include the exterior fire hydrants and a fire line loop around the building it serves, including the pipe size. This will be designed by the civil engineer. By “looping” the site, there will be good water flows regardless of which fire hydrant location is used and still provide good simultaneous flow to the building sprinkler risers. The city’s potable water piping can be used for this, but larger buildings will typically have a dedicated fire system with a backflow preventer. The civil engineer will obtain flows and pressures from the chosen connection point and design the underground piping and exterior fire hydrants. This loop will then be routed to the building in one or two locations as risers require. There are often conflicts with existing utilities, storm drainage systems, and other structures that must be addressed by the construction estimator.  If possible, these items should be identified prior to completing the estimate.  If this is not possible, it is usually advisable to include an allowance or contingency for these items.

2) – Building Sprinklers and Their Required Risers
NFPA and the AHJ will govern the number of risers required based upon the building size and hazard classification. Risers typically range from 3” - 8” diameter pipe for estimating purposes. If engineered riser sizes are not available, the required riser size can be estimated based on the engineer’s underground main pipe size to the building and the above riser requirements and NFPA. The 3” riser size can be used on smaller buildings with good city residual pressures at the highest sprinkler point of 50 psi as on the attached example. Larger riser pipe will be estimated on the area allowed and/or a long pipe run and/or a lower existing city residual pressure. If the building has “extra hazard”, the allowed area is dropped per NFPA and the AHJ. “Extra hazard” is defined in NFPA based upon the use of the space and its relative risk in the event of a fire. The hazard rating should be stated on the construction documents.

The sprinkler spacing should be based upon the coverage area allowed per NFPA and the hazard classification. The AHJ or Factory Mutual may also reduce those allowable areas to much less than NFPA requires, based upon the specific case. All fire sprinkler systems require an alarm system, whether they are a simple water flow gong on a small residential installation riser or a distributed digital control (DDC) system with smoke sensors, heat sensors and pull stations at each exit pathway on commercial and industrial projects.

For the example in this estimate, we have included a flow switch with internal relay in the riser assembly to which the alarm controls electrician will terminate. This is a typical commercial/industrial choice. Sprinklers installed in finished office ceilings always require an escutcheon trim ring at the hole. The escutcheon is not just a finish trim piece for architectural looks to hide the holes’ edges from view, but an important component in sprinkler and fire system design. The escutcheon prevents smoke and heat from rising into the ceiling space or floor above. This concentrates the heat from a fire on the sprinklers’ fusible link, allowing the sprinklers to activate quickly, as designed. Sprinkler installers will provide labor for the required hydrostatic leak inspection tests as part of their scope, and the estimator should always estimate this labor cost as well.

3) – Additional Potential Cost Items
All fire risers, specialty systems and fire extinguisher locations require signage costs. The local AHJ will often require a Knox box for each main building entrance. This Knox box is installed with the building’s master key inside the “safe”, for fire department use only.

The Knox box is installed on the outside of the building so the fire department won’t have to break into the building and damage excess property during a fire.  All sprinkler installations require a spare sprinkler head cabinet stocked with sprinkler heads and a replacement wrench for each type of sprinkler. Should a sprinkler be accidentally struck and release water, the local fire department will respond, and can then replace the head onsite and re-pressurize or “rearm” the system. allowing the occupants back in the building quickly.
 
Flanged or threaded connection, FM- and UL-rated valves with tamper switch and flow direction indicators are required instead of standard plumbing valves. Rising stem gate valves for visual verification of open flow conditions, or butterfly valves with open/close indicators are typical specifications to fire riser assemblies. These higher cost valves must be included for an accurate estimate. Victaulic exterior compression-type pipe connection fittings (instead of threaded connections) are common in the 3” and higher pipe sizes.
A 4’ exterior building overhang or larger will require sprinklers outside of the building envelope. Any obstruction 48” or larger inside the building will require a fire sprinkler to be installed underneath the obstruction. If a wood joist system is used, sprinklers are generally required above the ceiling in the joist space, as well as below the ceiling, for area coverage (See details belows). Penetrations through fire-rated walls and their required fire caulking, and routing around existing building systems and structure, can make these estimates challenging.

A complete estimate for installing a sprinkler system in an existing building will include firestopping on each penetration through a fire-rated wall. Seismic bracing of piping is required in some seismic zone municipalities, as well as seismic pipe connections. Fire department connections are commonly referred to as (FDC). A building is typically required to install an FDC for each fire riser, to give the fire department a water source close to the building,. Scissor lifts should be included in estimates for large jobs to promote productivity, and boom lifts for extremely high installations.



 

Overview of Labor, Material, Indirect Costs and Approach to Markups
Labor and equipment costs are calculated on a per hour basis and are typically determined based on the prevailing wage rates. Because of the need to account for so many things other than pipe installation, we will calculate labor and equipment costs in this estimate based on 8-hour days and a 40-hour week. The crew for this estimate is two or more.
Material costs are based on the takeoff quantities, and the estimator should include waste factors. It is also important to include the costs of freight to the project. Material quotations are solicited from pipe and fitting manufacturers and dealers. In addition to labor, equipment, and materials, quotations must be solicited from subcontractors to provide surveying, asphalt pavement restoration, and saw-cutting.

Indirect costs that will be estimated are permits, payment and performance bonds, temporary facilities and taxes. The contractors must calculate their own home office and project management costs. The standard estimating factors for indirect costs must also be accounted for by the construction estimator. Job trailers, office trailers, material storage, and temporary facilities must be included.

Special Risk Considerations
As with all underground projects, conflicts with existing utilities, footings etc., may require the estimator to anticipate additional costs not immediately evident.  For example, the estimator must factor in the effect of inclement weather on trenching. The estimator should also consider potential issues such as slower production rates from double shifts or night work; multiple trades mobilized simultaneously results in slow productivity; union vs. open shop; longer crew drive times; scarcity of staging areas; shoring of non-cohesive soils on deep trenches and flowable backfill in public traffic areas will all contribute to the cost estimate. Projects involving larger quantities of materials will have lower unit prices than projects involving smaller quantities.  Productivity should be considered for a heated or air conditioned building versus a building that is not enclosed.

Ratios and Analysis – Testing the Bid
Previous bids and square foot take off numbers for fire sprinklers and cubic foot numbers for computer rooms etc. are excellent to test the estimate. Variables that will affect this number upwards and downwards include all the exceptions and details noted above. Cost per square foot for fire sprinklers is a good test if all exceptions are accounted for outside the square foot take off and the estimating spreadsheet details these costs separately.  It is always a good method to maintain your database of historical costs and to then adjust numbers for geographic location, yearly inflation and economy of scale on large projects to test the estimate.


Other Pertinent Information
Permitting costs can vary significantly from location to location. Some AHJs perform a design review for no cost, and some municipality’s design reviews cost thousands. Plan review cost is important, as the sprinkler submittal and permit fees are often overlooked by the owner. The cost of controls and an air compressor for a dry sprinkler system will need to be included.  Fire booster pumps may be required if the existing flow from the public connection proves inadequate. Mechanical engineering costs may be required to design these systems if you are estimating before the construction drawing bid stage. A controls system for the fire pump will also be required and is included in the attached assembly estimate. A sample rough order of magnitude estimate of $150,000 is shown in the example for the entire pump/controller/water tank for a remote private well building scenario. 

This is an excerpt from the new Ninth Edition of Standard Estimating Practice, published by BNi Building News in June, 2014. Standard Estimating Practice is written by the American Society of Professional Estimators and is an invaluable  reference manual on the practice of estimating construction projects. This new Ninth edition, along with providing practical estimating guidelines, covers estimating plumbing in a healthcare center, HVAC digital controls, basic integrated automation systems, facility electrical power generating and storage equipment, electrical communication systems, security camera systems, fire alarm systems, and much more. This new edition provides the basic techniques of estimating, along with the “how-to” of applying these techniques to real life estimates.

Tags: Costs, Estimating Construction


1 Comments

  • Jun 13, 2014 Nick Ferrazano says:

    FDC connections are not a water soure for the fire dept. They are used for the fire dept to pump water into the system to increase the pressure and volume of water to the fire.


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