Part 9 in Jeff's series on errors in estimating discusses conditions.

Last month, we began our discussion of conditions and how they are an important aspect of the mistake making process in estimating. This month, we’ll continue this important discussion.

In estimating, there are a multitude of conditions that must be recognized, identified, quantified and analyzed for their affect on labor, material and equipment cost burdens. In our limited format in this advice column, we cannot hope to cover each and every type of condition an estimator may encounter in the course of a career as an estimator.

Open to above/below

Commonly identified on the design drawings with the abbreviations O.T.A. (Open to Above) and O.T.B. (Open to Below), they are commonly delineated with a dashed line “X” (for open to above) and a solid line “X” (for open to below). Open-to-below is one of the most critical conditions commonly overlooked by both inexperienced and experienced estimators. For example, partitions enclosing the perimeter of a mezzanine, escalator or atrium space must be distinguished from those walls of the same type elsewhere on the floor plan for they are open-to-below for one side of the partition. The framing and insulation can be installed from the floor side as can be one side of the single or multiple layers of gypsum board panels comprising the assembly. However, the side adjacent to the open-to-below space is distinct based on two critical factors:

• Considerably lower labor production

• Scaffolding/lift costs

The same factors/considerations for installing walls apply for any/all: fascia/soffit/ceiling work to be performed in areas that are open-to-above/below. Perhaps wood planks or metal platforms can span the open area and there upon temporary scaffolding can be placed. If not, fixed-in-place scaffolding from the floor below or scissor lifts may be required to gain access to the area above. Often, the general contractor provides such scaffolding so that multiple trades can access the open area—but not always. You must determine the scope of work for providing such scaffolding/work platforms before submitting your bid. If it is the individual trade contractor who is ultimately responsible to provide such access, very often trade contractors requiring such access make agreements with one another to share the cost and use of such equipment.

Whenever tradesmen are working in open-to-above/below conditions, they are in harm’s way and safety precautions must be taken. These precautions do, however, adversely affect labor production significantly. I’ve seen experienced estimators, who should know better, completely overlook this important condition. I asked one such estimator how he accounted for the extra costs involved when he did not make any effort to highlight it in his estimate. He said he simply added a few extra feet in his measurement around open-to-below spaces to account for any additional costs. That is a very risky tack to take—it may or may not cover the true cost.

Better to distinguish such conditions on your survey sheets and analyze it separately for all supplemental costs. Many trade contractors lose their profit margin or get into red ink on jobs due to such oversights—it can be their Achilles’ heel.

Within shafts

Akin to open-to-above/below conditions, work to be performed within mechanical or, more typically, elevator shafts, must be recognized, identified, quantified and analyzed separately from like assemblies that do not require installation from within a shaft. Quite common for this condition are demising walls between back-to-back elevator banks. Such walls are most commonly found in large office buildings with multiple elevator banks. Such a wall provides a fire barrier between these back-to-back elevator banks that typically is required by the building code. Another assembly whereby access within an elevator shaft is always required are “cant strips.” These are typically required to prevent items from lodging on projections within the shaft. Typically, it is a piece of shaftliner secured with utility framing components at a 75-degree angle from the edge of the projection back to the surrounding wall of the elevator shaft. It can be difficult to quantify this condition or even determine from the plans whether or not it is actually required. For this reason, it is often presented as a unit price (per linear foot) rather than a lump-sum price based on a guessed-at quantity.

In general, there are two ways to work within an elevator shaft. The first and most common is to plank-out the shaft opening with strong planks made of dimensional lumber. This is a simple span from one end of the shaft to the other (width-wise) with proper bearing on structural elements and no gaps between planks. The second and safer method is to use the top of operating elevators as a work platform. This may not always be possible or practical. In any event, work performed within a shaft is inherently the most dangerous type of work a drywall contractor can perform. It’s important that safety harnesses be worn at all times and all OSHA and other regulations pertaining to hazardous work conditions be strictly conformed to. I once worked for a company that lost two carpenters—they fell to their deaths while working in an elevator shaft.

As with the aforementioned open-to-above/below condition, these safety precautions reduce labor productivity significantly and typically require a team approach rather than an individual working alone. As well, the cost for creating a safe work platform that can access the work area must be considered as a cost burden under the equipment/scaffolding category on your cost summary. I always distinguish this condition, within shaft, above all others. Such a wall can easily cost double that of a like wall elsewhere on the floor plan. Likewise, a cant strip—which is a relatively simple assembly—has a high installed cost due to its hazardous location.

Difficult access

Aside from those conditions that present inherent danger to the workmen simply by their location above open areas/shafts, there are those conditions that have supplemental cost factors due to their location adjacent to elements that hinder installation. For example, it is very common for the core of an office building to have restrooms adjoining the elevator banks on one or both sides. Under these circumstances, it is typical for there to be a chase space (for the rough plumbing serving the fixtures) between the elevator shaftwall face and the furring that conceals the rough plumbing. This rough plumbing represents an obstacle to the easy installation of the elevator shaftwall assembly thus it must be recognized, identified, quantified and analyzed for cost separately. Likewise, if that very same elevator shaftwall was behind diagonal steel bracing (typical at the core), it too represents a “difficult access” condition and must be dealt with in the same manner. A rose may be a rose by any other name but a wall is not like any other wall when a difficult access condition exists.

For fascia/soffit/ceiling work, very often the mechanical/electrical/plumbing “spaghetti” suspended from the deck above can cause a difficult access condition to exist. For example, a large trunk duct may interfere with attaching hangers to the deck. In such a case, it may be required to bridge the duct and suspend hangers from that bridging. Such conditions are not always easily identifiable and experienced estimators always include labor/material allowances to cover such contingencies. W&C