New Kitchen Floor Plywood thickness

[bluecon]

I bought some 3/4" by 2 1/4" maple to redo my kitchen floor.
Altogether about 180 sq ft. Part of the kitchen is a newer addition on the house and it is 1/4" higher than the the original part of the house.
The newer higher addition has 5/8 inch plywood. If I switched this to 3/8 inch plywood the floors would match. Is 3/8 plywood to thin to underlay the 3/4 inch maple. The beams underneath are on 16" centers.
I prefer to not raise the lower part of the floor since the present height will match the floor heights at the doorways.

[garager]

I bought some 3/4" by 2 1/4" maple to redo my kitchen floor.
Altogether about 180 sq ft. Part of the kitchen is a newer addition on the house and it is 1/4" higher than the the original part of the house.
The newer higher addition has 5/8 inch plywood. If I switched this to 3/8 inch plywood the floors would match. Is 3/8 plywood to thin to underlay the 3/4 inch maple. The beams underneath are on 16" centers.
I prefer to not raise the lower part of the floor since the present height will match the floor heights at the doorways.

Let me see if I'm getting this correct. Your have a sub floor at 5/8" right now w/no underlayment on top of your subfloor, is this correct?

Now you want your subflooring to be a 3/8" material?

Your new addition was built higher than your old part of the house, with less thickness of a subfloor in the new addition and yet its still higher.

Did you slap that builder on the back of his head??????? :slap:

That is if I read your post right of course.

A subfloor and underlayment, should not be less than 1 1/8" thick, then your finished flooring on top of the underlayment.

I have seen what I said when trying to analyze your post. # times in my life I have see the old flooring sloped up to the new addition, thanks to the builder who couldn't read a dang tape measurer.

I will keep a close eye on this thread, it has certainly grabbed my attention. Maybe I can help you, just need a little more info, and a picture of the area would be of great help. Any how, explain this for me, you should have 2 layers, before you lay down your finished flooring, or 1 thick subfloor of 1 1/8".

[bluecon]

Let me see if I'm getting this correct. Your have a sub floor at 5/8" right now w/no underlayment on top of your subfloor, is this correct?

That is correct for the floor that is in the newer part of the house.

Now you want your subflooring to be a 3/8" material?

That would easily solve the height problems.

Your new addition was built higher than your old part of the house, with less thickness of a subfloor in the new addition and yet its still higher.

That is true. I removed 3 layers of linoleoum floor and 2 layers of 1/4 board from the original and one layer of linoleoum from the new addition.
Did you slap that builder on the back of his head??????? :slap:

The addition is newer than the original house but was there when I bought the house.

That is if I read your post right of course.

A subfloor and underlayment, should not be less than 1 1/8" thick, then your finished flooring on top of the underlayment.

Didn't know you needed to go that thick.

I have seen what I said when trying to analyze your post. # times in my life I have see the old flooring sloped up to the new addition, thanks to the builder who couldn't read a dang tape measurer.

The floors were level since the layers on the existing evened everything out. I think the builder purposely built to that height instead of tearing up the existing linoleum.

I will keep a close eye on this thread, it has certainly grabbed my attention. Maybe I can help you, just need a little more info, and a picture of the area would be of great help. Any how, explain this for me, you should have 2 layers, before you lay down your finished flooring, or 1 thick subfloor of 1 1/8".
Thanks for the info.

[garager]

OK, then I did read it right. Now, I'm glad I ain't doing your place.:D Teasing

Um, I don't have much time for today, I'll be back in the morning. Anyhow, whats the flooring like in the old section, is everything at the same level?

Can you build up the old part to meet the correct height of your new kitchen.

As a builder, I cannot tell you its ok to go to 3/8" for a subflooring, or even your existing 5/8". There are codes that we must follow. I have a feeling, your not going to be able to eliminate an elevation difference, unless you build up the old part.

Who ever did your job was a hack, they didn't know better, The floor joists should all be at the same level, new to old, then build up from there. So this could be they used larger joists in the new part. Because possibly your old section was not up to code for joist requirement. Well I maybe getting to deep, I'll back down for now, there can be many reasons for whats going on, but what can you do for a code requirement floor.

Build up the old section, to the proper floor requirement in the kitchen. This means both areas will have to be built up. But if your old section is built w/2"x6"s and a span that is greater the what code requires, now your biting into to big of a chunk...

Keep the kitchen one type of flooring and the the room another type w/a slight step up. Show me pictures, as I said before, then I can see whats going on in all directions. Gotta go, I'll be back in the morning....

[Ikester]

One must always be mindful of code requirements of course but honestly I can't see a problem laying 3/4" hardwood over 3/8 ply IF fir ply is used, floor joists are spaced at a standard 16", and the hardwood strips are laid perpendicular to joist direction. The safe approach would be to place 1/4" underlay on the original floor to match a 5/8" subfloor decking in the addition before installing the hardwood.

1 1/8" was mentioned as minimum subfloor decking + underlay thickness. That's a new one on me. Under ceramic tile yes but hardwood?

[bluecon]

OK, then I did read it right. Now, I'm glad I ain't doing your place.:D Teasing

Um, I don't have much time for today, I'll be back in the morning. Anyhow, whats the flooring like in the old section, is everything at the same level?

Can you build up the old part to meet the correct height of your new kitchen.

As a builder, I cannot tell you its ok to go to 3/8" for a subflooring, or even your existing 5/8". There are codes that we must follow. I have a feeling, your not going to be able to eliminate an elevation difference, unless you build up the old part.

Who ever did your job was a hack, they didn't know better, The floor joists should all be at the same level, new to old, then build up from there. So this could be they used larger joists in the new part. Because possibly your old section was not up to code for joist requirement. Well I maybe getting to deep, I'll back down for now, there can be many reasons for whats going on, but what can you do for a code requirement floor.

Build up the old section, to the proper floor requirement in the kitchen. This means both areas will have to be built up. But if your old section is built w/2"x6"s and a span that is greater the what code requires, now your biting into to big of a chunk...

Keep the kitchen one type of flooring and the the room another type w/a slight step up. Show me pictures, as I said before, then I can see whats going on in all directions. Gotta go, I'll be back in the morning....
The joists are 2"*8"s on 16" centers. I have no camera at this house. will post pictures when I get one. I think I should tear the floor up to see what they did.

[garager]

1 1/8" was mentioned as minimum subfloor decking + underlay thickness. That's a new one on me. Under ceramic tile yes but hardwood?

I'm not saying this is a code requirement, just when we build, we like to put down 1 1/8" sheathing. Not always, do the HO have their minds made up on the flooring materials and I'm not going to allow for any soft spots, but this isn't a case for 1 1/8", no argument there. Also, not always do I go with 1 1/8", for wood floor, but never will I ever go less than 3/4" subfloor unless forced to, sorta as this type of situation, tiles most certainly though at 1 1/8", especially if they are 18" tiles .

He should go with the safe approach and raise the old flooring, that is my recommendation. Now even with 5/8", if he uses any short flooring, this could still have an effect with softness underneath his new floor. If he is using long stuff, he shouldn't really have a problem. A bouncy floor can have a bad effect with the new flooring.

Another suggestion, is to beef up under the subfloor between the joists, but that is a tremendous amount of work, and needless to say it would be difficult. But if the new flooring is bouncy between joists after installed, that is another option. This is a good topic, I would like to see other carpenters or contractors jump in and have their say so.....

Mark

[bluecon]

The new addition is only about 36 sq ft of floor space.
I still need to paint the cupboards and have a while to decide.
Right now I am thinking to put new 5/8" plywood in the new part and build up the original part with 1/4". What is the proper 1/4" to use for that? Presently there are 2 layers of 5/8" plywood in the original section.

Is it possible to build up between the joists with blocking of plywood and/or 2 * 4"s and then lay a 3/8" plywood on top of that?

[garager]

Another suggestion, is to beef up under the subfloor between the joists, but that is a tremendous amount of work, and needless to say it would be difficult. But if the new flooring is bouncy between joists after installed, that is another option. This is a good topic, I would like to see other carpenters or contractors jump in and have their say so.....

Mark

The new addition is only about 36 sq ft of floor space.
I still need to paint the cupboards and have a while to decide.
Right now I am thinking to put new 5/8" plywood in the new part and build up the original part with 1/4". What is the proper 1/4" to use for that? Presently there are 2 layers of 5/8" plywood in the original section.

Is it possible to build up between the joists with blocking of plywood and/or 2 * 4"s and then lay a 3/8" plywood on top of that?

Yes, not easy to do, but it will work.

Minnesota State Residential Code Book

Allowable spans and loads for wood structural panels for subfloor sheathing and combination subfloor underlayment.

Span Rating 16" OC Subfloor sheathing Minimum thickness 5/16" and Underlayment of 19/32",5/8"

Almost 1' there guys, this is for Minnesota, your state maybe different.

For a 1/4" underlayment (your build up) you can use partical sheathing if you'd like. Just stager the seams of course.