Second of Two Parts

Now that we have counted the ways that good dimensional lumber can go bad, let’s see how this actually the whole unfortunate process in action—so we know how to prevent it.

Board of Education

A 100+-year-old school building was to be renovated with costly new six-inch fir lap siding, custom cut to match the old siding. Some noteworthy items about wood siding:

• It is typically delivered to the jobsite factory-primed on all six sides to prevent moisture intrusion.

• A board’s grooves and joints are fabricated so that there’s only one way to install them. Each has a definite “A" side (the good side) that faces the exterior and will be seen, and a definite “B” interior side that faces the wall and won’t be seen after installation.

• A siding manufacturer’s processes are designed so that the “A” side is handled carefully from fabrication to delivery, so that the factory-applied primer remains intact and pristine. The “B” side primer may have runs and drips as well as marks and dents acquired from tooling, contact with steel rollers and drying racks, or other stages of the handling and delivery process. This is not considered a problem, because no one will see the B side after installation.

Failing Grade

After all the new siding was installed on the school walls, the paint inspector arrived to oversee the finishing work. To his surprise, he saw numerous flaws on the newly primed siding.

A typical "B" side finish is shown at left. Unfortunately, in this case, it was applied to the exterior "A" side while the pristine  finish (right) is on the interior "B" side.

Upon further inspection, he concluded that the siding manufacturer had made a critical error: The primer was, essentially, inside-out. The “B” side had a pristine coat, but the exterior “A” side had the dents, marks, and runs typically found on the “B” side.

Now what?

The widespread marks and swirls in the primed surface were likely to telegraph through even multiple coats of intermediate and topcoat, which would lead to a highly unsatisfactory appearance.

Making it Right

The inspector ordered a mock-up on a section of siding to see if this was the case—and indeed it was. The uneven texture in the primer and surface flaws were still evident after application of the intermediate and topcoat.

So, all the siding had to be sanded and a full coat of new primer applied to cover the many bare spots left after sanding, bringing unbudgeted costs and delays. 

Moreover, if an oil-based primer had been specified for the factory application, environmental restrictions would prevent that product from being applied at the jobsite, so a water-based primer compatible with the finishing system would need to be substituted.

How Could This Have Been Prevented?

Ideally, the general contractor would have inspected the siding when it was delivered, noted that the primer flaws were on the wrong side, and rejected the shipment.

Even if it was missed at that time, the carpenter or GC certainly should have noted the problem after the first few boards were installed, and then stopped the installation.

At that point, the remaining boards could have been sent back and replaced by the manufacturer. Alternatively, the sanding and re-priming could have been done on the ground or in a shop setting.

Either method would have been faster and more efficient than doing the work after the siding was installed!

Editor's Note: This article was excerpted from Coating Specialist Training materials and PQA Inspector Dave Lick and is reprinted with permission from the MPI (Master Painters Institute). MPI content describes best practices for commercial, institutional, and light industrial painting.