Old House Remodeling:

Patching Thin Hardwood Flooring

In This Article:

The jagged edges of existing flooring are cut back to a straight line, a thin spacer material is added, and salvaged 3/8" oak hardwood flooring is installed.

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Skill Level: 3 (Intermediate) Time Taken: About 2½ Hours

By , Editor


While remodeling an old house we decided to add some closets and change the locations of some doorways. The new bedroom door joined two areas that already had thin hardwood flooring, but previously were separated by a wall.

This house has 3/8 inch thick oak flooring in most of the rooms. I believe the flooring was installed many years after the house was built in 1898. For instance, where we've removed flooring on the second floor, we've found that the tongue-and-groove subfloor is painted, a sure sign that the subfloor was once the finished floor surface.

Standard hardwood flooring is 3/4" thick. If hardwood flooring is installed as an after-thought, 3/8" or 5/16" flooring is usually installed.

This rough-looking area between two existing hardwood floors was created when we cut a new door opening in an interior wall.


The ends of the boards were quite staggered, which is normal for an edge that is covered with trim.


I used this Porter-Cable 6½" circular saw to make the major cuts. This saw has the blade on the left of the motor, where most circular saws have the blade on the right. I used this saw because it's easier to handle than larger circular saws.


This saw also comes with a dust collector fitting, which I need to keep the saw dust to a minimum.


The dust collector fitting plugs into an opening in the front of the saw.

I duct-taped a 1¼" shop-vac fitting to this metal piece, so I had a dust-collecting circular saw.


I laid out the cut, using a 4' ruler.

I used the small speed-square to make sure the line was perpendicular to the existing flooring boards.

A framing square would work too, and it might be more accurate.


With a sharp utility knife I scored a line in the existing hardwood floor surface.


Then I went over the line with a pencil to make the line easier to see.


A close-up of the scored and marked line.


I made a plunge cut with the circular saw and then cut along the line.

While I made this cut free-hand, I could have rigged up a cutting guide board. That seemed like too much work for two small cuts.


A closer view.

The red arrow points to the line I followed. Of course, I needed to make the right-hand surface of the blade follow this line.


The circular saw can only cut until the saw body hits the doorway. Then I need to use other cutting methods.


This is the Fein Multi-Master, which costs about $200. It's a lot of money for a tool I don't use often, but it's worth every cent.


I used the narrow saw blade to cut the last few boards.

The blade just vibrates slightly. If you touch the blade it won't cut your skin, yet it cuts wood reasonably fast.

This blade did not come with the tool... I had to buy it separately for about $35. Fein's accessories are not cheap.


A closer view.

The Fein Multi-Master is a true flush-cutting saw, and can cut right up against an obstruction.


After making the cuts I used the sanding head to smooth out the rough edge of the cut boards.


Using a steel ruler, I made marks 9 inches away from the first cut.

My flooring is 1½" wide, so I needed to use a multiple of 1.5 for the width of the patch.


Actually, making the second cut slightly less than 9 inches would be a good idea. If the last board is too wide and needs to be ripped narrower, that's fine... but if the last board is a fraction of an inch too skinny, that's a problem.

After I marked the line, I cut the ends of the boards with the circular saw, and finished up with the Fein Multi-Master.


Close-up photo of the second cut.

Notice the slight bevel on the corner of the cut (between the two arrows). This bevel should reduce the chances of something snagging on the cut edge after the patch is installed. If one of these boards is cupped too high, a sharp corner will catch on things and split the wood.


Sub-Floor Preparations:

A small problem:

The sub-floor is made from 1x4 tongue-and-groove planks, and the boards have all cupped over the years, leaving these high spots at the edges.


I used a random-orbital sander with 40 grit sandpaper to sand down the high spots.


The patch area after sanding.

Note that there are several holes in the subfloor. These are from electrical wires that we moved during the remodeling process.


I nailed a piece of aluminum flashing over the holes. This should provide better structural support.

The old flooring was installed over a layer of burlap, so without special filler material the new flooring would be lower by about 1/16 inch.

I looked at Home Depot for some type of thin filler material but came away empty-handed. I guess they don't make 1/16 inch thick Masonite.

For a spacer material, I decided to use some leftover scraps of vinyl siding, which is about .040 to .050 inch thick (compared to 1/16 inch, which is .062 inches)

I simply stapled the strips of vinyl siding to the floor.


Flooring Installation:

I installed the first piece of flooring.

I face-nailed the back edge, since there was no tongue to connect with the groove.


Then I carefully nailed the tongue edge, driving the nails into the corner where the tongue meets the edge of the board.


Close-up of brad nail in tongue.


I also tried some 18 gauge staples, but they tended to split the wood too much.


For the next pieces, I used a scrap of flooring as a tapping block, to avoid hammering directly on the flooring.


Since I was using salvaged flooring, I had to clean up the crud on the edges and the tongue of the boards. I used a couple of different carbide paint scrapers.


Critical Detail - The Last Piece

I staged these two photos to illustrate the method I used to install the critical final piece of flooring.

I used a table saw to rip the tongue off the last board.

Using a small bench belt sander, I sanded a slight bevel on the cut edge, so the board could be tilted into place.


When installed, the top edge should fit snugly against the ends of the original flooring boards.

There is a slight cavity below that final edge, but nobody can see it.


For the last piece, I had to carefully tap the board into place. This was a tight fit


I had to face-nail the last piece.

(I later used some wood putty to cover the nail heads.)


The completed patch.


Later, I sanded the floor with a 3-head random-orbital floor sander. I rented this sander from Menard's, but Lowes also rents the same machine.

There are 3 grades of sanding discs sold alongside this machine: 36 grit, 50 grit and 80 grit.


I also used a 3"x21" belt sander to grind down the small areas that needed more serious material removal. Using this sander I could apply a higher pressure on a smaller area than the big machine. This also worked well for sanding around the edges of the room.

I used 40 grit sanding belts for heavy-duty sanding, then I followed with the random orbital sander using 50 grit sanding discs.


This photo shows the same spot after the floor was refinished, the new door hung, and the trim installed.

The perpendicular boards create a slight accent in the overall appearance of the floor.


When looking at the larger scheme of things, the flooring patch is barely noticeable. You can see it at the lower right.



More Info:

Tools Used:

  • Basic Carpentry Tools
  • Steel Ruler
  • Miter Saw
  • Table Saw
  • Pneumatic Brad Nailer
  • Air Compressor
  • Carbide Paint Scraper
  • Bench Belt Sander

Materials Used:

  • Oak Flooring, 3/8" Thick
  • 1" Brad Nails
  • Aluminum Flashing
  • Vinyl Siding Scraps
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Copyright © 2006, 2007  HammerZone.com

Written July 25, 2006
Minor Revisions, January 9, 2007