How would you guys fix this subfloor back down?

Submitted by Luckosaurous t3_10papog in DIY

So I’ve had to lift the floor to get a room re-wired and will be moving the radiator in shot to the other side of the room. The problem is that I’ve had to cut through the floor about 15cm from the nearest joist. It’s a real struggle to reach the next joist as it’s beneath a stud wall and the hot water tank is installed above it so I can’t really access anything other than what you can see in the pictures.

My thoughts were one of two options, but I’m keen to see other peoples thoughts/experience/ideas:

  1. ⁠Cut some big triangular wedges and attach them to the side of the joist that you can see to support the overhang.
  2. ⁠Run a smaller cross brace between the joist you can see and the one under the water tank, and use pocket hole screws to attack it to the far joist under the water tank that you can’t see (fiddly, will probably result in lots of swearing) and just a regular screw through the near side joist into the cross brace.

Other considerations; I may be overthinking this, but screws don’t really grip end grain well, so rather than screw through the joist into the end grain, should I set up another piece of wood next to the cross brace/wedge so that the screw from the joist can hit face grain and then go side grain onto the cross brace/wedge?

Basically any help an experience you’ve had will be warmly welcomed. In particular I’m worried about a creaking floor in the aftermath.

Images as I’m probably not explaining very well

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Comments

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moe_70 t1_j6jcshf wrote

Your overthinking this way too much, cut a 2x6 and put it under the floor bellow the trim, use 3.5 inch wood screws and go into the baseboard till you get into the 2x6.

Cap off your floor, screw it back in and fill the holes in the baseboard.

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BadSanna t1_j6jdgmv wrote

No one is going to be walking over there. Just grab a 2x6, cut it longer than the hole, put it in horizontally and screw through the joist then use deck screws through the subfloor on either end. Should be plenty strong enough and easy to remove if you need to access what look like pipes in there.

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BadSanna t1_j6jdyw8 wrote

Also, you should block between the joists in the center bay so the cut breaks over the block to avoid the small cutout section bowing differently when someone steps on it. 2x4 should be fine, but 2x6 would fit and be better.

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BadSanna t1_j6js7i1 wrote

Replying to Luckosaurous (#1,624,422)

What? No. The missing piece should be one section.

I'm saying screw through the far joist into a horizontal block perpendicular to and aligned to the top of the far joist in the small bay against the wall. Make that block longer than the width of the hole so you can also screw down through the subfloor into the block at the ends. That will be enough to support the subfloor in the narrow bay against the wall if someone steps there for some unlikely reason.

Then you should also block along the seems in the center bay so the missing piece of plywood has support under the break. Just regular vertical blocks. It's called "boxing out."

You would do the same for like an attic access hatch, so there is support along every seem. You don't need to bother with the one inch gap between the double joist and the next one, that's too small a space to deform even if someone leaned on the exact spot with a cane or something.

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Exotic-Flight3452 t1_j6lmkp3 wrote

You need to add a no other 2x4 to support the end against the wall. You can do this from the other side of the wall if possible. If not, make a 2x4 3”-4” longer than the opening. Put it under and first attach the existing floor from the top. Then put the subfloor back on top and screw it down.

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EnvironmentalBath185 t1_j6mfkai wrote

I’d just “picture frame” the inside of the square and add a center brace to prevent bowing; the frame gives you all good screw points. Good luck.

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Luckosaurous OP t1_j6mggwv wrote

Thanks for all the responses everyone!👍🏻

As usual I think I was trying to over engineer the problem and make it so that an elephant could walk on it but it seems general consensus is that a simple baton running under the stud wall but overhanging the gap with some screws on both sides of the join into the baton should suffice.

I’ll probably still put a couple of triangular wedges in anyway for my own peace of mind as I’m a bit ocd about jobs being solid, but very much appreciated, thank you! 🙏🏻 🍻

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