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replacing section in subfloor


Synicasm's Avatar
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06-08-11, 02:17 PM   #1  
replacing section in subfloor

I have a roughly 4 x 6 section of subfloor I am replacing and one end of the piece that is 4 feet wide will end up being between two floor joists. Will simply adding some extra 3/4 inch plywood underneath the seam between the joists and screwing through the 2 pieces of 3/4 inch ply be enough to support the between joist seam that is not supported by any joist.

 
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06-08-11, 02:24 PM   #2  
Can you cut out a bigger piece to get to the middle of the joist?

 
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06-08-11, 02:29 PM   #3  
No unfortinatly the next joist is under neath a doorway and i think its too far away to add a sister board to the Joist. I was thinking of adding a couple 2x4 perpendicullar but cant figure how to attach the ends of the 2x4's to the joist under the door.

 
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06-08-11, 02:54 PM   #4  
Sounds like a job for pocket screws or toenailed nails - I'm assuming you can get to the joist, just not the other side to nail through it?

 
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06-08-11, 03:12 PM   #5  
Don't use plywood for a cleat. Use dimension lumber. Sister a 2x4 along the joist to give you a good nailing/screwing surface. Not sure why you can't reach it. Plywood won't give you the strength you need on edge. Can you get under the house and fit the boards that way? Certainly installing cross bracing would suffice and may be better since your doorway is not not sitting on anything.

 
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06-08-11, 03:34 PM   #6  
The joist is about 8 inches back under the subfloor section I cut out.. I am working from the top If i can avoid it i dont want to go underneath to avoid cutting into the belly wrap.

I think I will try to Pocket screw / toe nail it a couple of 2x4's inside joists looks to be the best option.

Thanks for the advice

 
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06-08-11, 04:26 PM   #7  
I don't think pocket screws are appropriate for a floor load. You should be toe screwing or toe nailing.

Can you cut the subfloor all the way back to the joist that is through the doorway? Then put 2x material between the two joists to carry the edge of the new piece of plywood.

 
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06-08-11, 05:34 PM   #8  
If the long dimension of the plywood is running parallel to your joists, you are running your plywood the wrong direction. The long dimension of the plywood needs to be perpendicular to the direction of the floor joists.

Unless you have some weird layout, the 4' wide ends of your plywood should always fall on the 16" layout of your joists. I understand what you are saying about the next joist being beyond the wall/doorway. In addition to providing some end blocking under the wall and between those last two joists, it could be that you need to make a joint in the opposite direction that you are planning.

If your partition wall is bare, you can lay that end blocking flat underneath the wall and sink a screw down through the sill plate and subfloor to suck it up tight against the existing subfloor. A little subfloor adhesive between the two would be a good idea too. That will hold it for you while you try to toescrew the far end. Good place for an impact driver and some torx screws. Or a palm nailer and some 16d's.

 
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06-10-11, 03:22 PM   #9  
The long 'cut' Dimension will be running perpendicular to the joists. After looking at it last night the actual overhang is about 4 inches then a break and another 10 inches or so that go under the door frame before the next joist of the existing material. The original sub floor is particle board .. ( not OSB ) and are in something like 12x12 feet sheets. So if you will imagine I am replacing one corner section of about 6 x 4 feet. I ended up adding cross 2x6 pieces perpendicular to the joists where I could using a combination of toe nailing and end nailing basically allowing for 3 of the 4 edges of the piece I plan on replacing to be supported . On the 4th edge I am using a 2x4 to (I think its called cleat ) the remaining particleboard and 4 inch overhang the new plywood. I think this will be stable enough. If not Ill probably end up having to add some more in between joist pieces on the final edge to support it.

 
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06-10-11, 05:26 PM   #10  
The particle board is in 4x8 sheets. I can't imagine picking up a 12 x 12' sheet of anything As long as you have all the seams covered, you should be good to go. What are you replacing the particle board with? Has the existing particle board swollen? Will the edges meet well?

 
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06-13-11, 12:23 PM   #11  
This is a Mobile Home.. The pieces of particle board they used on the sub-floor are not 4x8 sheets. I imagine they used these gigantic sheets when building the home at the mobile home factory

Everything matched up well and the extra supports I added seem to be working well.

Thanks!

 
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