Hardwood Floors April/May 2019

Sanding Aesthetics Causes and Cures (Continued) AT THE SITE

• Abrasive related: – Poor-quality or improperly manufactured abrasive – Contaminated or damaged abrasive – Improper abrasive selection or improper abrasive sequence • Site conditions: – Substrate-related issues causing equipment malfunction – Se led or otherwise unlevel or loose ooring • Harmonic vibration: – e structural integrity of, or (parallel vs. perpendicular), seams not ending on joists – Undersized joists, undersized beams/supporting joists, improper joist or beam span (end-to-end or between joists/beams) – Flooring installed parallel with oor joists – Insu cient or loose fasteners, incorrect fastening schedules, etc. – Structural integrity of the oor being sanded – Sanding of loose, poorly installed, or oating wood oors undulations in, the sub oor – e undulation of the oor from joist truss de ection – Improper sub oor thickness, insu cient sub oor orientation

– Older, historic wood ooring installed directly to oor joists resulting in more de ection between the joists – Any sub oor or wood oor systemwith “built-in-give,” such as with some gym oor systems

COMMON CURES Refer to NWFAWood Flooring Sand and Finish Guidelines for proper sanding processes. • e structural integrity of the sub oor system is not the responsibility of a wood ooring contractor unless he or she installed the sub oor system. Structural-related issues should be addressed by a quali ed professional. • Resand the oor at a minimum 7- to 15-degree angle with the big machine on the rst cut to a en the oor. Sanding at the opposite angle on the subsequent cut may also be necessary to a en the oor properly. Avoid cross-grain sanding (perpendicular to the direction of the grain) on any area of the oor if possible. • No repairs may be necessary.

Download and purchase copies at nwfa.org.

One of the most important factors to keep inmind is that every wood oor will show sanding marks on the nished surface. e reason is that every oor that gets nished requires sanding. Some sanding marks may be visible, and some may not. Evaluating these sanding marks is where some ambiguity comes into play.

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