Opening Tolerances: Understanding Details Can Help Control Costs

By Craig Carson

When I started in this industry, the project documents we’d bid from were always 100-percent complete. There was no such thing as schematic development (SD), design development (DD) and finally construction development (CD) levels. Today we never see a 100-percent complete set of documents for bidding, and we’re sometimes asked to provide pricing early from conceptual sets of documents.

This started when the construction community had to change to survive the late 1970s. That was when we were hit with wild inflation and architects and owners turned to a concept called “fast tracking.” This was a way to issue sets of construction drawings in phases, getting those items under con-tract before inflation ate up more of the budget. We’d see civil, foundation and structural documents issued first, followed by mechanical, electrical and plumbing, and then architectural. Interior and landscaping came later.


This was when the change to the SD, DD and CD way started. We had to follow the plans and specifications strictly because the architect had time to develop the complete set of building documents before we saw them for bid-ding. Back then, architects were more precisely involved with the details and knew the tolerances of the products and disciplines of the building trades more than they typically do today.

There were many reasons for this: tighter reins on their fees, more owner intervention, as well as design-build coming into play to help hold costs down. Personally, I like where we are today and getting involved earlier in the projects. But still, we need to remind architects and general contractors (GC) about construction tolerances.


How many times have you been sit-ting in a design meeting with the project architect and GC going over system details, and pointed out that the caulk joint cannot be the ¼- or ½-inch dimension shown on a manufacturer’s systems detail? Why? Because it won’t accommodate the construction tolerances of the surrounding materials and the required size of the caulk joint from the sealant manufacturer, and still perform its critical duty. Taking all of this into account, you see why ¾-, 1-inch or even larger caulk joints should be required.

Manufacturers of standard glazing systems don’t comment on what size caulking joints need to be used with their products. This makes perfect sense; it’s not their responsibility to choose the caulking materials. The caulk joint sizes on their details have been carried over from past details for decades. The details just represent the need for caulking between the framing and the other building materials.

I’ve found that architects often resist this reality. After all, they’re concerned with the aesthetics of the project, get engrossed in the details and lose sight of the scale (sometimes losing sight that we don’t stand back, look at the building and say ‘Wow, if only the caulking joints could be smaller.’). However, we need to protect the building owners, the architects and, more importantly, ourselves from potential failure of the systems.

So, look at your openings and become familiar with the tolerances allowed for the surrounding materials and installation. Review the worst-case scenario and then add your recommended joint size for the span of the framed opening from the caulking manufacturer. You might surprise yourself on what this will add up to. Review this before you bid the project so you can provide the correct budget to caulk your framing. Larger joints not only add material, but also labor to caulk and properly tool. Cover costs in your bid, and as I’ve said before, the devil is in the details.

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