Mistakes in the Plans

I’m old enough to remember when plans were drawn by hand. A designer who wanted a particular detail had to physically draw that detail line by line, considering each line as it was drawn.

That’s not what happens today. A designer who wants a specific detail simply finds that detail in some old plan set. The designer clicks to copy and clicks again to paste into the current drawing. Little thinking is required. The result: All sorts of nonsense can end up in the plans. As the contractor, it's your job to find mistakes like this. First, I'll explain how. Then I'll explain why.

Bill Mitchell, an architect friend, recommends using a checklist to find design errors. Every item on this list has some impact on cost. 

The Six Cs of Plan Review

Examine each of these categories separately. First, look for anything that’s missing. Are the plans complete? Then do a second review to be sure plans and specs are consistent. Continue through the list one “C” at a time.

Complete – Are the plans an accurate and thorough representation of what’s intended? Is every detail that’s called out in a bubble actually drawn somewhere? Are enough sections shown to define the project?

Consistent – Is each sheet of the plans consistent with every other plan sheet? Are the plans consistent with what’s in the specs? Find yourself a light table. Overlay sheets on each other, one sheet at a time. Does the ceiling plan match the floor plan? Do light fixtures fall where air conditioning grilles are already located? Do plumbing vents on the roof pass through heating and cooling units?

Clear – Ambiguity in plans is the enemy of productivity. Good plans require the least improvisation. Are all key dimensions called out? As a contractor, you’re entitled to scale dimensions off the plans. But if there’s room for several interpretations of what’s required, do you bid the worst case or the best case? Plan details are usually the last step in the design process. A set of plans light on details will be heavy on change orders.

Correct – Begin by checking the length of one outside wall. Add up the chain of dimensions along the entire wall. Then check the full length of the opposite outside wall. Checking to the center of walls isn’t good enough. That makes the framer do the math. Be sure the two dimension chains match. If they don’t, it’s called a bust in the plans. When you’ve checked the length of all opposite outside walls, begin checking dimensions of inside walls. When you’re sure all wall lengths are right, start checking wall heights.

Constructible – Every designer is perfectly capable of drawing plans that can’t be followed at any reasonable cost. Be sure the plans allow enough space for trade contractors to complete their work. For example, does the plenum above a ceiling have space for both duct and conduit? In a residence, be sure framing details leave enough room for drain lines. If space is tight, your plumber, electrician or HVAC contractor will find a way. But you may not like the result.

Cost – Designers aren’t always sensitive to cost issues – either construction cost or the cost of maintenance. Favor materials that are readily available and that can be installed using conventional construction techniques. For example, almost all construction materials come with square corners. Building a semi-circular wall requires forcing square materials into a round shape. It can be done. But waste will run up costs with little benefit.

How to Protect Yourself

Architects and engineers use contracts that shift responsibility for finding design flaws to the contractor. You’ll see “verify in field” stamped on many plan sets. Whether you see “VIF” or not, both law and common sense give you, the contractor, at least shared responsiblility for errors on the plans. If you aren't eager to accept liability for mistakes by others, use Construction Contract Writer to shift liability back where it belongs. The trial version is free.