How Many Times Can My Floor Be Sanded?

Pre 1900 Hardwood Floors

This period pre-dates the wider spread use of regular tongue and groove hardwood floors. Thicknesses vary all over the place but a common lies in the one inch range. Considering these floors have no tongue and groove the floor can be sanded more times than others providing nails are set along the way and continue to hold the floor intact. The only potential drawback bay be in the structural support of the thinner flooring without a subfloor. Thinner flooring would tend to be less structurally sound. Excessive squeaking and creaking would be a symptom of this kind of thickness.

These floors are much easier to asses in how much hardwood is left to sand off. Simply find an area that shows the original floor joists below, inset a business card or similar until it rests on the floor joist. Make a mark, remove and measure.

Older Tongue And Groove

Most older tongue and groove floors were manufactured with a thickness of 3/4 of one inch, with some almost one inch. However the floor cannot be sanded successfully with good results below the tongue and groove area without exposing nails used to install the floor.

Methods use to determine the amount of hardwood above the tongue and groove are similar to pre 1900 types. If there is any gapping present between boards, insert the business card remove and measure. The business card will rest on the tongue portion of the board. Prior to any measuring, vacuum any dirt that may be trapped in the area.

Another measuring option includes checking the perimeter of in floor heating vent openings. Remove the vent cover and check the condition by eyesight looking at the tongue and groove (image below) profile.

Exception: Post World War II hardwood floors milled in the USA would sometimes be 5/16" thickness without being tongue and groove. This time period ranges from the mid to late 40's due to the lack of available supply.

Newer Tongue And Groove

For all common tongue and groove floors the frequency in when they can be refinished or sanded depends on how much hardwood is left above the tongue and groove. The first illustration shown indicates a new solid pine floorboard. Thickness from top to bottom is 3/4 of one inch. The arrow indicates the amount of hardwood above the groove area. For brand new floors the measurement runs in the 1/4 inch range.

Micro Beveled Prefinished Floors

Throw in the wild card on this one. How many times these floors can be sanded will depend on what appearance you want to achieve. Most times the bevel will have to be sanded completely out to achieve a desirable look. Otherwise chances are good you will be left with a non uniform bevel depth appearance. This is not the fault of the floor finisher, but rather the condition of the overall flatness of the floor before sanding.

Inconsistent flatness will cause the drum sander to remove more material in some places and not another. How much is removed to reach a smooth bevel free floor depends on the depth of the original manufactured bevel. Some full beveled floors popular in the seventies have a depth greater than 1/8 of an inch. Most newer prefinished floors manufactured between early 1990 and today offer a shallower bevel or in the 1/16 inch range and less.

Engineered Hardwood Floors

Here's where things get a little different. How many times will depend on the wear or veneer layer of the product. Let's say for instance you just purchased a Bruce Lock and Fold floor from Lowes. The amount that can be sanded or refinished off the top is minimal. The photo on the right best illustrates the situation.

Considering the overall thickness is only 3/8" (top to bottom) one can get a  good idea how thick the top layer is. It's located at the point of the arrow in a darker shade. Simple math makes it look like the surface layer is 1/8" the thickness of the board; making the top layer about 1/16 of an inch thick--- if that! In a perfect world a very good professional could sand this floor once but we wouldn't have any money on the bet.

Other better engineered floors in the 3mm range could possibly be sanded twice and not the three times many manufacturers lead you to believe.