Hardwood Floors February/March 2017

RESOURCES

By Brett Miller

NWFA Sand and Finish Guidelines Update Highlight

In June 2016, the NWFA released updated guidelines for the sand and finish processes. One of the areas that was updated involved sanding direction using the big machine (belt or drum sander):

These changes were made by suggestions of many of the subject matter experts within the wood flooring industry to help ensure a higher quality end-result in the final sanded product. The direction of the cut from the big machine (drum or belt sander) is the first step in ensuring a properly sanded, flat floor. NWFA Members can download a PDF of the full Sand and Finish Guidelines at nwfa.org or order a hard copy from the NWFA Online Store. • NEW GUIDELINE – The first cut should be at a 45 degree angle to the wood grain; the second cut should be on the opposite angle to the wood grain using the next appropriate grit of sandpaper. All subsequent sanding cuts with the big machine should remain at an angle to the wood grain to prevent dish-out of the material. The cut angle on the floor will be dictated by the many variations in grain direction, species and condition of each individual floor. Use the last sequenced grit, not skipping any grits between sanding cuts. • OLD GUIDELINE – the first cut with the big machine should be at a 7-15 degree angle to the length of the boards. • NEW GUIDELINE – the first cut with the big machine should be at a minimum 7-15 degree angle to the length of the boards. More aggressive angles (up to 45 degrees) may be necessary to achieve a flat surface in extreme cases. Wider plank floors, excessive overwood/underwood or uneven flooring systems may benefit from a steeper angle first cut. The more uneven the flooring surface, the steeper the angle of the cut should be. When the first cut exceeds a 15 degree angle, the subsequent straight cut must be made with the same grit paper used on the first cut at the exact opposite angle. • OLD GUIDELINE – when sanding parquet patterns the first cut should be at a diagonal; the second cut should be on the opposite diagonal using the next appropriate grit of sandpaper and the final sanding cut with the big machine should be parallel with the room’s longest dimension, using the last sequenced grit, not skipping more than one grit between sanding cuts.

The 1st cut should be at a minimum 7-15° angle to the length of the boards.

Subsequent cuts should be parallel to the length of the boards.

All cuts should be at a 45° angle to the direction of the wood.

Illustrations courtesy of Lägler

the magazine of the nat ional wood f loor ing associat ion

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