How to repair plywood floor?

[lift mechanic]

I built my dream shop a couple years ago using 1-1/8" T&G plywood. Rolling my tool boxes and mobile machinery around I have noticed some small spots (4" x 6") that have sunk below the rest of the floor. There must have been a void in the plywood under the surface. My question is how to repair them? My thought was to make a template and route out the area sort of like you see in other areas of the plywood (boats) and over lapping on the larger (1) area. Any other thoughts on how to repair the floor. The floor is painted with a floor polyurathane paint.

[tomsteve]

you might be able to cut the area out, glue and screw some 3/4" thick supports around the perimeter underneath, then set a patch in.

[Splinter Puller]

I built my dream shop a couple years ago using 1-1/8" T&G  plywood. Rolling my tool boxes and mobile machinery around I have noticed some small spots (4" x 6") that have sunk below the rest of the floor. There must have been a void in the plywood under the surface. My question is how to repair them? My thought was to make a template and route out the area sort of like you see in other areas of the plywood (boats) and over lapping on the larger (1) area. Any other thoughts on how to repair the floor. The floor is painted with a floor polyurathane paint.

Yes... just route out the blemish to the depth of the flaw and glue in a dutchman patch.

[Snipe Hunter]

Yes... just route out the blemish to the depth of the flaw and glue in a dutchman patch.

[Wild Turkey]

My concern is that the problem could be deeper than a void so make sure you check what's left of the floor after you route the recess.  If it's still soft you may need to cut it out, screw an oversize patch beneath the floor, then fill the hole with another patch.

Voids are the #1 suspect, but make sure you solve the whole problem so it doesn't migrate.

( and please don't ask me how I know this


 !)

[tomsteve]

My concern is that the problem could be deeper than a void so make sure you check what's left of the floor after you route the recess.  If it's still soft you may need to cut it out, screw an oversize patch beneath the floor, then fill the hole with another patch.

pretty much why i suggested the same. routing out the bad plys then there is only a couple plys supporting the dutchman-theres a good possibility that it will still be spongy.

[Splinter Puller]

pretty much why i suggested the same. routing out the bad plys then there is only a couple plys supporting the dutchman-theres a good possibility that it will still be spongy.

I figured it was common sense that if the void was deep then you do a dutchman in layers with each layer an inch larger then the one below.   I guess this was not implied.   

You don't even have to be too worried about the thickness of the patch matching as each subsequent route will mill the patch flush with the new recess.     The layering would only be needed if the void was deep in the floor... which it is most likely not as a deep void would not telegraph through as a weak spot in the first place.  common sense folks.

[Cooler]

For that small of an area I would use a high compressive strength epoxy to level it and use a belt sander to make it even with the rest of the floor.  Even if it only lasts a few years it would be a good approach.

https://www.masterbond.com/properties/hi...ve-systems

[lift mechanic]

Thanks for the replies, good suggestions. I would think on 1-1/8" plywood the void even if 1/2" deep would not weaken the area. but I will check for softness before putting the dutchman patch in. All the depressed areas seems to be 1 layer down in the plywood, so I guess I will be spending a couple hours on my knees.

[Snipe Hunter]

You could also cut out the bad spot with a hole saw if it's small enough. Make a template out of MDF or something and use an angled router bit to cut a chamfer around the diameter of the hole. Make a round slug with the same thickness plywood, also with a chamfer. Make sure the slug sits flush in the hole and glue it in. If it's too big for a hole saw, use a jigsaw set at an angle and cut a square/rectangle hole and make a plug to match. It's a very strong repair.