Special Inspections
Some building departments require “special inspections” for the bolts, holddowns, and plywood. These are performed by third party companies. Each special inspection costs $1,000. $650 for the special inspector and $350 to us to do the coordination.
Bolt Inspections:
For the bolts, they usually want to physically watch us tighten 25% of the the bolts with a special socket wrench called a torque wrench. They want us to do this even though we always install the bolts with impact wrenches similar to what mechanics use to tighten bolts on tires. Impact wrenches tighten a bolt far beyond the limits of a torque wrench.
We use impact wrenches because they are fast and the bolts are very tight.
Perhaps the strangest thing about this is that tightness of bolts has zero impact on the sliding resistance of the bolt. 1 month after a house is built all the nuts on the foundation bolts are loose because the mudsill shrinks after it dries. At this point you can remove the nuts by hand. If tight bolts were a serious matter, re-tightening the bolts after the mudsills shrink would be a code requirement. Special inspection companies are invariably owned by engineers, who have a lot of influence on building departments, and they profit from redundant special inspections.
Types Of Special Inspections
There are two other types of special inspections.
Plywood Inspections: If plywood nails are spaced less than 4″ apart on the edges the building department will probably require another special. For these inspections the inspector stares at the nails for 10 seconds and says “Yep, they are 3″ apart” and you are billed $1,000.
To avoid this expense we used to install the nails 6″ apart and when the inspector left we would re-nail the plywood 2-3″ apart. We do this because a retrofit with nails 3″ apart is twice as strong as a retrofit with nails 6″ apart and 25% stronger than a retrofit with nails 4″ apart. This webpage explains the importance of nail spacing.
Recently we changed policy and now charge you for the plywood special inspection so we don’t need to come back after the inspector is gone. We do what we can to prevent the building department from making us do it wrong.
Holddown Inspections: Holddowns requires bolts be placed in holes that are dust free. The special inspector will be checking for dust after we drill the hole in the concrete. The holes we drill are dust free. We use a special bit attached to a vacuum that removes all the dust when we are drilling holes in the concrete. Some building departments require pull tests which only special inspection firms have the equipment to perform. Pull
