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nickdu 07-25-2009 09:16 PM

Removing subfloor
I've got some questions regarding removing a subfloor. I'm thinking of removing the subfloor in my mudroom so that I can build it up for a tile floor. If I do remove, as opposed to just adding a layer on top, I'm wondering the steps needed to remove.

From the reading I've done it looks as if I need to cut the floor at the walls and add blocking at the edges so that I have a spot to nail, or screw, the new subfloor into. This blocking is where I have the questions. When I cut out the floor at the walls it seems as if I could end up, worst case, with the subfloor under the base plate overhanging the previous floor joist by about 14 inches (on the wall that runs parallel to the floor joists). How does this section of subfloor get supported? Also, I read that if the base plate is not over a floor joist, as in the case I just mentioned, when you cut the subfloor at the wall the wall might move a bit and cause cracks.

What is the procedure for doing this? I've got an unfinished basement below.

Do I attempt to find out where the cut is going to end up and put the blocking in first so that the wall is always supported?

When the blocking is added so that I have a spot to nail the new subfloor into, is 1/2 of it supposed to support the floor on the other side of this new floor (the existing floor under the base plate)?


Bud Cline 07-26-2009 10:35 AM

WHY are you doing this? To buid up a floor you must ADD to it not remove it.:)

Seriously - What are you thinking?:)

nickdu 07-26-2009 03:56 PM

Yeah, sounds crazy. I don't think I can build up to the 1 1/4" that's suggested because I have an adjoining room where the finished wood floor is only 1/4" to 3/8" above the mud room subfloor so I think I would potentially have a transition problem. Here are a couple thoughts going through my head:

1. Remove the 5/8" (not sure if it's tongue and groove) and replace with 3/4" T&G only. Not the 1 1/4" that's recommended but it gets me 1/8" more. Plus I don't have to scrape off the left over thinset that's on the subfloor now.

2. Someone suggested just add 1/2" plywood on top of the 5/8", ditra and tile. They said that would put me about 5/8" above the adjoining floor which is transitional. That sounds good, but the tile we purchased are 12x24 and I'm told the floor needs to be very very very flat. I haven't checked the flatness yet but I'm guessing I'm going to have to flatten it. SLC will probably be needed so that would add to the floor height. Not sure if the transition would still be doable.

3. Get to 1 1/4" by building up the floor from below. This is an idea I had which I haven't proved out yet. Someone said it should stiffen the between joist subfloor (which I'm trying to do). Anyway here is the idea. I would remove the 5/8" since working from above might be easier. I would lay down 3/4" T&G. Before securing I would mark where the floor joists are from the unfinished basement below. Then pick back up the sheet and add 1/2" plywood strips where the markings are. I would glue and then screw in from above. Then lay the sheet back down and secure to the floor joists. Now between the joists I have 1 1/4" subfloor. Ledger boards were suggested but I'm not sure these are required. I believe the between joist floor will be stiffened regardless of whether there are ledger boards or not.

Well there you have it.


Bud Cline 07-28-2009 08:34 AM

Clear as mud!!!

Too complicated for me I'm afraid. I found myself dozing off while trying to read and understnad that plan.:)

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