Nowhere is the profitability of a sprinkler installation project more dependent on sound engineering than a retrofit job. It’s the accuracy of the conceptual piping layout that will make or break the labor estimate. And if the installer works off a plan that was hastily prepared by a design engineer who only visited the jobsite once or twice, then he is going to have to make so many field alterations that he may as well be credited with engineering the job himself.
With a little ingenuity and a significant amount of engineering, the amount of elbow grease expended in a retrofit can be substantially mitigated.
Preliminaries: When designing commercial retrofits, it is prudent to seek out the building engineer and pick his brain. It is good fortune to run into some leather-faced guy who has been working in that building for years, who knows the whole plant inside and out, and may even have some old architectural plans.
After rummaging through all sorts of questions regarding the structure, explain that part of your job entails configuring how to run some large piping from Point A all the way over to Point B at a remote end of the building.
The operative theory here is that people love to help out other people with a problem that they are well prepared to solve. More times than not, the old building engineer thinks for awhile and soon comes up with an exceptionally good plan, one that saves the engineer a design headache.
Only good things can happen when “talking shop” with someone who is mechanically minded and also has a degree of emotional investment in “his” building, where his days are filled with repairs, upkeep and maintenance.
Another important preliminary step in any retrofit application involves asking the local fire marshal if CPVC piping can be used. If piping is to be concealed, the use of CPVC should be of top priority.
The lighter piping places a lessened load on the existing structure. Installers refer to the speed in which plastic pipe can be hung as “lightning” due to its overall quickness of operation. It is lightweight, easy to cut and more flexible than steel pipe. This is especially of benefit on retrofit projects, where “cut-in-field” slowdowns can kill the job’s profitability.
If the system is to be dry, such as for unheated attics, CPVC cannot be used, but a smart contractor will save considerably on labor if he utilizes attic sprinklers. One of the sprinkler industry’s major product improvements, attic sprinklers produce their largest cost-savings when they are used in existing attics - an installer’s worst nightmare. Developed in the early-1990s, they are listed for varying pitches of roof slope, on wet or dry systems, and were the first sprinklers ever to be listed for extended coverage in combustible construction.
Extended-coverage sprinklers of all types are a godsend for those retrofitting any building. Provided that adequate water pressure is available, these automatic sprinklers reduce the total number of sprinklers needed in virtually any building, thus reducing the number of fittings and also labor time.
Where available space above ceilings is minimal, these sprinklers can be supplied by exposed piping that may be painted or concealed in soffits. There are plenty of soffit manufacturers that market their wares to fire sprinkler installation firms specifically for retrofit applications.
Unfortunately, it is a truly rare instance where ESFR sprinklers can be retrofitted in an existing building, as the voluminous installation requirements contained in Chapter 8.12 of NFPA 13 bode badly for AHJ acceptance. The average existing structure contains too many obstructions and structural conditions that are not conducive to the demands of the NFPA code regarding ESFR heads.
The legwork also must include a water supply analysis, building survey and a preliminary layout in accordance with NFPA 13.
Particularly in multistory buildings, the reality of getting pipe in place must be addressed. For high-rises, delivered pipe lengths are usually kept to 12 feet in length, as they must be carried up stairs or in an elevator, and then fed through ceiling grid to be wiggled between structural members for proper placement. When ceiling tiles are to be removed and replaced, the sprinkler contractor can expect that many tiles will be soiled or broken, and should figure on buying any number of new ones before the job even starts.
Labor-Saving Ideas: Always remember, a quality retrofit design strategy is all about minimizing labor. Using the following rules-of-thumb makes the job less daunting:
- Seek to minimize the number of wall penetrations, particularly at masonry walls.
- Avoid running piping near large obstructions, such as air-handling equipment.
- Make absolutely certain that the cross-main (large piping) can be installed where shown on the plan. Any mistakes made on main or feed piping will constitute an installation disaster.
- Use fast-installation products wherever possible.
What little space existed above the ceilings to route fire sprinkler piping was congested, especially in the middle portion of the structure.
Since the installation time for any one floor would be multiplied by 22 when tabulating total cost, the creation of an efficient piping scheme was crucial. After “playing” with the hydraulic calculations, what worked best for each floor was to run two 2 1/2-inch mains at each far end of the building - where mechanical obstructions were few. Nine 1 1/4-inch lines connected the mains, with a tenth 2-inch branch line used near the standpipe connection, which “carried” the bulk of the water flow in the grid center.
The use of grooved-end piping with 1-inch welded outlets provided a key function. What clearly hastened the installation was the fact that the mains could be hung in place without any problem to commence the work.
Similar installations have been made by contractors who prefer to send all grooved pipe without welds, and direct their veteran installers to drill for mechanical tees in the field, spotting heads along the way. While this may shorten engineering outlay and get installation started quickly, it is actually an engineering-by-osmosis “blind” approach that ignores the real danger that onsite obstructions represent. The sprinkler spacing strategy gets compromised as a result, as do the hydraulic calculations.
How Much? The toughest call for the engineering firm involves generating a bid number. Dollar amounts of contractor proposals usually exceed what was forecasted. What represents the lion’s share of the difference is the installation of a satisfactory water supply and anticipated field-labor time. Naturally, if there is to be excavation for a new underground feed main, right away you’re in excess of $15,000.
If you have to install a private water source, such as a pressure tank, that’s another major expenditure, and that assumes there is somewhere for a tank to be placed. Once that matter is settled, an estimator scratches his head for days attempting to ascertain the most difficult aspect of his bid, which is predicting how much labor will be eaten up to install the system(s).
If he’s lucky, he is looking at a CPVC installation that will go in quickly. But he is often bidding a steel-pipe job with no existing plans.
Every retrofit project presents a unique challenge. The whole idea in retrofitting a mechanical system into a building is to make the process as painless as possible for everyone concerned. The greater percentage of the early fire sprinkler installations were retrofits, and this fact alone was responsible for the concept of using engineers so that the piping could be prefabricated for the installers.
A retrofit project at its onset is a measure of engineering skill to most effectively control a complicated task while causing the least disruption, in order to meet that project deadline. If it were easy, there would be no need for competent designers.
