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french_guy 05-14-2013 01:16 PM

replace a subfloor?
 
How difficult it is to replace a subfloor?
I currently have OSB, not very flat and squeaking in some spots. I had some issues in the master bedroom (I'm installing laminate), and tried to fix it the best I could without removing the subfloor – but I am partially happy with the result
For the other 2 rooms, I was thinking I could maybe replace the subfloor myself?

I understand the current subfloor has to be cut along the wall (baseboard and door casing have to be removed) with a circular saw, recip saw or even better a toe-kick saw? Depending on the saw used, a stripe of subfloor will remain along the walls
Then use a prybar to remove all nails, and step by step tear out board by board
Then check the level and put some shims if necessary on top the joist
Then put the new subfloor (3/4” T&G OSB or 3/4” plywood with deck screws and glue)
But was about “blocking”?
For the walls being perpendicular to the floor joist, I assume I will have to put some piece of wood (2 x 4 stud?) in between each joist, to make sure the edge of the new board will be flush with the stripe of old subfloor and more importantly be supported underneath. By the way, how those piece of stud should be secured to the joist? Nails, screws, glues, specific metal plates?
But what about the edges that are along the walls parallel to the joists?
And do I need to have blocking under every edge?

Hope I was clear in y explanation…

Thanks

MJ Force 05-14-2013 02:33 PM

I've had to do this in a large bathroom to access the plumbing. With my skill saw I cut 2" away from each wall and removed the entire subfloor. The 2" remaining lip allowed me to screw and glue backing (2x4's). A constant 2" lip allowed the room to remain square which made lay the new T&G subfloor easy. Glue and screw all outer edges of the new floor to the backing.

MJ Force 05-14-2013 02:40 PM

Unless you have some serious deflection issues with your floor joist, I would not try to shim out the subfloor. Glue and screw your new subfloor to the joist. Slight leveling issues could be addressed with floor level compound over the new subfloor.

french_guy 05-14-2013 02:48 PM

Sorry for my ignorance, but what do you mean by "backing"?
Do you mean a piece of stud glued and screwed half under the lip, the other half being for the new subfloor?

MJ Force 05-14-2013 02:48 PM

Is the OSB that bad of shape that you must replace it? Or would adding more screws help, you think? And then pouring floor level in the trouble areas.

french_guy 05-14-2013 02:49 PM

Quote:

Originally Posted by MJ Force (Post 1179325)
Unless you have some serious deflection issues with your floor joist, I would not try to shim out the subfloor. Glue and screw your new subfloor to the joist. Slight leveling issues could be addressed with floor level compound over the new subfloor.

Actually, I have a serious deflection in the hallway, but for that I am trying to get a quote from a carpenter....!!!!

MJ Force 05-14-2013 02:49 PM

Quote:

Originally Posted by french_guy
Sorry for my ignorance, but what do you mean by "backing"?
Do you mean a piece of stud glued and screwed half under the lip, the other half being for the new subfloor?

Yes! Exactly. It works well if glued and screwed.

french_guy 05-14-2013 02:54 PM

Quote:

Originally Posted by MJ Force (Post 1179329)
Is the OSB that bad of shape that you must replace it? Or would adding more screws help, you think? And then pouring floor level in the trouble areas.

Not sure, will have to see when the carpet is removed...
What type of screw are best to use? I have used regular coarse screws in the previous room, but one of the contractor who came to look at the hallway said it was the worst type of screw to use, not being strong at all (i have to admit some of them broke just under the head when I was screwing them wiht my Ryobi impact driver !!!)

MJ Force 05-14-2013 03:00 PM

Quote:

Originally Posted by french_guy
Actually, I have a serious deflection in the hallway, but for that I am trying to get a quote from a carpenter....!!!!

Again, this sounds exactly like the issue I had after I dealt with the bathroom. But not connected.
The upper hallway around a curved stairwell dropped 3/4" from edge to wall. I determined that there was no settling and that the framers just laid it this way. My Tile guy and I were able to level this off so it didn't feel like you were tipping over while you walked down the hall. We poured floor level compound.

MJ Force 05-14-2013 03:07 PM

Quote:

Originally Posted by french_guy
Not sure, will have to see when the carpet is removed...
What type of screw are best to use? I have used regular coarse screws in the previous room, but one of the contractor who came to look at the hallway said it was the worst type of screw to use, not being strong at all (i have to admit some of them broke just under the head when I was screwing them wiht my Ryobi impact driver !!!)

You may have used drywall screws by mistake. I can snap them with a screw driver. If you have any amount of screwing to do, rent an automatic screwdriving tool. Or ask your local hardware store for the correct fasteners.

ddawg16 05-14-2013 03:47 PM

I can't imagine using OSB for a sub-floor....it just not have the same deflection (same thickness) as plywood.

This is what my bathroom floor looked like...shower pan failed.

http://i43.photobucket.com/albums/e3...e/P8110008.jpg

To take out the old floor joists, I just cut them down the middle and applied liberal amounts of sledge hammer.

http://i43.photobucket.com/albums/e3...e/P8240018.jpg

The new joists went in easier than the old ones came out. I was also able to double up in a couple of areas.

On top of that I put 3/4" T&G plywood. Then anchored it with #10 exterior screws.

For reference....on the 2-story addition I'm working on....that sub-floor is 1 1/8" T&G....it's about like walking on concrete....I wish the rest of the house had the same.

french_guy 05-14-2013 04:03 PM

Quote:

Originally Posted by MJ Force (Post 1179345)
You may have used drywall screws by mistake. I can snap them with a screw driver. If you have any amount of screwing to do, rent an automatic screwdriving tool. Or ask your local hardware store for the correct fasteners.

No, it was not the black drywall screws, but the gold one.....not sure if they are any better though!!!

MJ Force 05-14-2013 04:12 PM

Quote:

Originally Posted by ddawg16
I can't imagine using OSB for a sub-floor....

Me neither. Who knows how much wetness that stuff can take during construction. I'll have to ask my daughter, she works in a big OSB plant in northern BC.


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