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Patching subfloor holes

J

JackOfDiamonds

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Jul 31, 2020
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706
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Idaho (USA)
During construction of my addition, we had a downpour before the roof was on. Water was pooling in the second floor with nowhere to go, and it was starting to run into the house. The contractors drilled several holes to allow water to drain down into into trash cans on the first floor. It was probably the right thing to do, but now I have these holes in my subfloor to patch.


1000015885.jpg

I'm thinking of screwing a block on the underside, then filling them with something, but I haven't decided what.
 
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C

cgrutt

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I just used JB-Weld Kwik wood epoxy stick to fill similar sized hole it worked good.
 
L

larry4406

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18,739
Location
Northern Virginia
Hole saw of choice, smaller the better to clear your hole.

Scrap piece of matching subfloor. Cut out a plug.

Using the waste, center it on your hole. Use it to guide the matching hole saw to create larger hole in the subfloor.

Construction adhesive applied to 2x4 block and apply it to underside, screw it from above. Add adhesive and install the plug and screw it in. Fill gap with adhesive.
 
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U

Ultradog MN

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Jan 20, 2024
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Twin Cities
I too will ask what you'll be covering it with. As @duneslider says If hardwood, dont bother.
If carpet or any kind of vinyl I would glue/screw a backer under it then fill with Rock Hard or Durabond.
Remember: Even an average sized woman can exert immense pressure in one spot if wearing high heels.
A big gal can exert up to a ton - or so I've read
 
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P

PCustoms

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Jul 23, 2011
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22,053
Location
VT
PugetDude said:
A 250lb woman putting all her weight on a 3/8 diameter spike heel is 2260 pounds per square inch...
Click to expand...

Damn, definitely don't use PVC then....


I have a few 2x4 holes to fill (kneewall supports thru floor). Put some adhesive on a scrap 2x, tacked it from below then went upstairs and pulled it tight with several construction screws. Then I cut a piece of the closest thickness plywood I had and glued that in from the top.

When it came time to do the flooring I had a few lips and low spots, as I was using the leveler material I did a smear over each patch. Had it just been these spots I would have used Bondo
 
C

cgrutt

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Mar 4, 2016
Messages
8,091
cgrutt said:
I just used JB-Weld Kwik wood epoxy stick to fill similar sized hole it worked good.
Click to expand...


Just to follow up with this hole was in cedar T&G floor board on front porch. I did recommend pulling up board and replacing it as well as several others but customer preferred to just fill the hole first. I advised that we could try that but no idea if it would work or how long it would last. Filled the main hole with JB-Weld Kwikwood epoxy stick followed by some short'strand fiberglass. Sanded and primed repair with oil-based exterior primer. Should be painting today.

Original hole

Screenshot_20260511_064103_Gallery.jpg

Hole filled and primed for paint

Screenshot_20260511_064136_Gallery.jpg
 
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