# Replacing a subfloor



## bvz

Hello all,

I am about to remove a tiled kitchen floor which is over 3/4 plywood which is on top of the original 1 x 10 (3/4" x 9.5") diagonal plank subfloor.  I am not sure if the plywood is glued to the subfloor, but I am willing to bet it is.  This may make is necessary to replace the subfloor (plus the bamboo flooring manufacturer might require a plywood underlayment anyway - I'm waiting to find out).

My questions revolve around what it takes to replace the subfloor.  From what I can gather reading this and other forums is that the process goes something like the following (I am wondering if you all could just take a look and see if I am on the right track):

1) Cutting out the old subfloor as close to the edges of the room as I can get using a circular saw.

2) Not worrying about the last inch to inch and a half that remains jutting out into the room.  Basically just leave that bit in place.

3) Checking the existing joists to make sure there is no damage or rot to them.

4) Building up new blocking underneath any edges (the edges along where the old subfloor was cut away) so that the new subfloor always has something supporting its edges.  This blocking should be 2x6?  Match the existing joists?  Something else?  How do I do it for a long 12' edge that is parallel to an existing joist but not directly on that joist?  Do I just install a new joist somehow? (seems hard)

5) Installing 3/4" plywood sheets "perpendicular" to the existing joists.  This might be just regular plywood or it might be special tongue and groove subfloor ply, depending on what kind of underlayment the flooring manufacturer recommends.

6) Filling in any cracks (and screw heads) with special compound (whose name escapes me at the moment, but which is designed to fill and level subfloors)

7) Using floor leveling compound to fill in any low spots.


Does this seem to be correct?  Am I missing any steps?  Any good books you can recommend I read before I dive into this?

Thanks in advance!

Ben


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## inspectorD

Is this what you are replacing it with? (plus the bamboo flooring manufacturer might require a plywood underlayment anyway - I'm waiting to find out).


1) Cutting out the old subfloor as close to the edges of the room as I can get using a circular saw.
This saves you from using a sawzall along the edges of the walls. As long as you use the same thickness, you will be fine, just clean up the old stuff.

2) Not worrying about the last inch to inch and a half that remains jutting out into the room.  Basically just leave that bit in place. Yup

3) Checking the existing joists to make sure there is no damage or rot to them. As best you can, usually you can see it from below, My guess is you have a crawlspace. 

4) Building up new blocking underneath any edges (the edges along where the old subfloor was cut away) so that the new subfloor always has something supporting its edges.  This blocking should be 2x6?  Match the existing joists?  Something else?  How do I do it for a long 12' edge that is parallel to an existing joist but not directly on that joist?  Do I just install a new joist somehow? (seems hard)
This is usually not necessary, it depends on how much deflection is in the floor(bounce). It is a good idea, and it is hard and time consuming...just do the best you can...if you have to. 

5) Installing 3/4" plywood sheets "perpendicular" to the existing joists.  This might be just regular plywood or it might be special tongue and groove subfloor ply, depending on what kind of underlayment the flooring manufacturer recommends.
Yes...always

6) Filling in any cracks (and screw heads) with special compound (whose name escapes me at the moment, but which is designed to fill and level subfloors) Not with wood floors.

7) Using floor leveling compound to fill in any low spots.
Only if it is drastic, unless you have a million dollar home. We call those floors with a little sway in them....character.

Does this seem to be correct?  Am I missing any steps?  Any good books you can recommend I read before I dive into this?

Thanks in advance!

Ben[/QUOTE]

Good luck, tell us as you get along, how its going.


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## bvz

InspectorD,

Thanks so much for taking the time to answer my questions!  I really appreciate it.

I'm getting fiber strand bamboo floors from teragren.  They emailed me today and ostensibly included installation instructions - only they forgot to actually include the instructions   Hopefully tomorrow they will get back to  me with the actual document and I can then determine whether:


I *most likely* have to replace the subfloor (if the old underlayment was glued down)

or

I *absolutely* have to replace the subfloor (if they require a plywood underlayment - in which case I definitely have to replace the subfloor)

I don't mind the challenge of replacing the thing, really.  The only annoying thing about the process is that I just spent the last 4 Saturdays lying on my back in the dirt in a tiny tiny tiny crawlspace installing all new wiring for the kitchen.  Once I remove the subfloor, I will have easy access to these wires and could have done THAT whole job in a day.  Sigh.  That's why home improvement is so much fun.   

Thanks again for your help.  I am trying to set up a quick and cheap digital camera hooked to my computer so I can do time lapse photography of the whole remodel (well... I already missed taking out a wall, but everything else at least).  If I succeed in that, I'll try to post a link to the video when I finish the project.

ben


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## inspectorD

Sounds like you have quite the project there. Keep it up, your asking the right questions. 
Have fun.


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## bvz

Ok,

So I never actually got the time lapse thing going (just too busy and I wanted to get started on the floor).

I have managed to get the existing flooring off and was lucky... the plywood underlayment was not glued down.  So that means I do not have to replace the whole subfloor.  Woo Hoo!

I had an installer come by today and look at the place and he says they can glue down directly to the existing subfloor.  First I have to pull up and replace couple of split, and one seriously cupped, planks.  After that I am going to screw down the subfloor to re-tighten it against the joists.  They are going to then sand the floor and then glue down the fiber strand bamboo.

This all sounds doable and much better than ripping the whole thing up.  So... happy days.

Thanks to all for their help.

Ben


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