How to patch hardwood floors.

Patching is a fiddly job, but not difficult. 

Hardwood Floors need patching when

  • Pet stains are just too deep (sanding can only fix so much)
  • Walls or cabinets are moved
  • Old vent or duct openings become obsolete

While tongue and groove flooring is modular and designed to allow for replacement, patching can be a fussy and tool-intensive process. Sometimes even small, seemingly innocuous patches require the use of a up to three types of saw (circular, chop and table), a router, a nailer AND a drill.

In general, the older the house, the older the wood; the older the wood, the less likely it is to a standard shape and size and the more you will work to get replacement boards to fit.

For non-carpenters, allow at least half a day to complete even the smallest patch. And don’t go rent your sanders until all your patching is done! Watch Bob do a pretty, laced-in patch on our YouTube channel!

First, replace any missing subfloor.

Cold-air return patches like these are a pain because the hole you’re fixing goes right through to the level below! All hardwood flooring – even small patched areas – needs to have subfloor underneath; hardwood floor alone isn’t strong enough to hold you and all your crazy stomping. And you won’t have anything to fasten the hardwood floor to without a subfloor.

But fixing a subfloor that is already largely covered with hardwood is like trying to change your underwear while you still have pants on: you’ll need to remove more than you want.

In other words, you’ll have to remove hardwood beyond the area you’re patching so you can get to the floor joists (which are usually 16″ on center) and then make sure that you screw the new subfloor to those floor joists. Then you can replace the hardwood floor itself.

There is a right way—and a wrong way—to design your patch.

You can finger-join your replacement boards back into the existing floor (above), or you can neatly frame and miter the outline of the patch.

If you’re not going to use a framed patch, make sure you stagger your board ends.

And we mean really stagger them; never have two adjoining boards end within 4″ of each other (this may mean that you remove portions of boards that are not damaged – but the sacrifice is worth it!)

Please don’t just fill the opening with a line of boards all the same length.

These two photos show how just ugly that is.

Bedoom202
Bedoom202

Remove the unwanted wood.

If you’re replacing an area where the tongue and groove are still intact, you’ll need to destroy at least one board; this will create enough space for you to get a pry bay under the adjacent boards.

The best way to remove that starter board is to use a spade bit to drill a large hole at each end and then use a circular saw (set the saw cut depth to exactly the thickness of wood to be removed) to cut two lines, connecting the holes.

You’ll take out the loose center piece with a hammer and a chisel, then carefully ease out the remaining two edge sections.

Now your pry bar will have a space to get under the other adjacent boards that need to be removed.

Fill the empty space with hardwood!

This is a good point to double check that you are using the right wood in your patch.

At the bare minimum, make sure you are using the same widths and species of wood. And, if you can, use wood of the same age, particularly if you are patching maple.

Use a chop saw to cut the boards to fit each row of your opening. For the laced-in patches, you’ll need a hammer or mallet to persuade the new boards to thread back into your staggered openings. If they can’t be persuaded with a mallet, you may have to open up your grooves or thin down your tongues using either a router or a table saw.

Blind nail the boards as you go using a flooring nailer or even just a pneumatic trim nailer held at a 45° angle.

Just be sure you’re using at least a 16gauge 2″ nail or staple – 18gauge trim nails aren’t robust enough to hold flooring. And any fastener labeled as a brad is definitely too delicate for this job.

Make sure you’re using a fastener about every 8 inches, with at least two fasteners per board (even if the boards you took out were nailed every 16″). If your patch finishes against a wall, you may to rip down the width of the final board to get it to fit, which is when a table saw becomes useful.

Can I just replace one single board?

Absolutely – just be extra careful not to damage the surrounding floor as you remove the sacrificial board. Cut a new board exactly to length to fit into the opening, but you’ll have to remove the bottom of the groove to get it to drop in.

Dry fit it first – if it’s too low, you’ll want to build up underneath with cardboard or rosin paper. Pre-drill and face-nail the board in place with 2″ trim nails or screws, preferably at an angle to improve holding power. If you haven’t had to shim under the board, you can use a squirt of construction adhesive instead of fasteners.

Don’t try to use filler to avoid a patch!

This is just shameful; don’t do it.

Filler is never meant to be used like spackle. This might be fine if you plan to paint or carpet over this floor, but if the wood is going to show, replace the damaged sections.

Pete’s Bonus Tips

We have everything you need, online or in our St. Paul, MN store.

Visit our online store from the comfort of your sofa or visit our cute store at 186 Fairview Ave N in St. Paul, MN. We've got everything you need for your project, and friendly people to answer your questions. 

Three installation definitions

End-matched

When even the short ends of hardwood flooring are tongued-and-grooved. This creates a superior holding on all four sides of every board. This is important because seasonal change can cause hardwood to change in both width and in thickness.

Board width change just creates gapping, but even a slight lift at the end of a board can create enough lippage for you to catch a toe! It also exposes that board end to chipping.

End matching keeps those short ends tight and level. Conventional milling puts a tongue on the north and east side of every board and a groove on the south and west edges.

Blind-nailed

When tongue and groove flooring is nailed at the tongue of each board, allowing the adjacent board to cover up the fastener, which means the floor is secured almost invisibly to the subfloor.

Even more important, the nails are at least a 1/4" from the surface of the boards, which makes for a much less risky sanding experience.

Top-nailed floors are a beast to sand because all your fasteners must be counter-sunk by hand or they might catch the sanding drum.

Relief groove

There is endless debate about the purpose of these grooves that are milled into the back side of hardwood flooring. The best explanation we've heard is that the grooves prevent the board from becoming "case-hardened" during the drying process.

This keeps the board from developing shinkage-induced interior stresses that would cause cells in its core to buckle and collapse. For the rest of us, the relief grooves tell us which is the face side of the board.

Spline (slip-tongue)

A narrow strip of wood that can slip into the groove of a piece of hardwood flooring and turn it into a tongue.

Because tongue and groove floors are always installed tongue-forward, spline allows you to change your installation direction in irregularly-shaped rooms.

Get a one-on-one phone consultation with a hardwood flooring expert.

For a small fee of $25, we can provide the wisdom and knowledge that you need to complete your hardwood flooring project.

When you don’t know what you need to do next, that’s when it’s time to call Pete’s Hardwood Floors Help Hotline.

An actual flooring contractor will answer all of your questions!

We have a crack staff with a range of specialties, from carpentry through floor machine maintenance, and we can troubleshoot just about any hardwood flooring mystery thrown our way.

If you are stuck or struggling with your hardwood floor project, one call could save you hours in the long run.