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-   -   1/2" sublfoor...what underlayment for hardwood? (http://www.diychatroom.com/f5/1-2-sublfoor-what-underlayment-hardwood-158560/)

Jrhenry24 10-01-2012 11:03 AM

1/2" sublfoor...what underlayment for hardwood?
 
Hi,
I decided to replace the laminate floors in my kitchen with hardwood. After ripping them up I found 1/2" plywood with 3/4" particle board underlayment. I ripped out the underlayment leaving only the 1/2" plywood subfloor.

1. What underlayment do I need to put down over the top so I can place oak hardwood strip flooring? What is recommended and what would you use in your own home?

2. What fasteners should I use to put the underlayment on top of the subfloor, and where do I place them?

3. How good of shape does the subfloor need to be in to prevent squeaking? I intend to nail or screw it down before placing the underlayment on it.

4. Roofing felt only between the underlayment and strip flooring?

5. Use glue for the underlayment to the subfloor with the fasteners?

6. Any other considerations?


Thank you for taking the time to read my post

hand drive 10-01-2012 11:27 AM

you also have to consider the thickness of the new underlayment when added to the new hardwood. For example, the laminate flooring was thinner than average hardwood so if you went back with 3/4" under layment and then the hardwoods on top of that then 1 1/2" would be total thickness. That will most likely put the hardwoods up into the baseboard zone and into all of the door jambs. Most houses I've seen with 1/2" sub floor had 5/8" on top of it equaling about 1 1/8" total thickness.

joecaption 10-01-2012 11:37 AM

Or better yet get rid of the 1/2 also. It's about useless as a subfloor and acts more like just 1/2 shims on top of the joist because it just sags between them.
Ypu can cut it out with a Toe Kick saw along the walls.
I'd then use 3/4 T & G Advatec as the subflooring with constrution adhesive on the joist and ether #8 ring shank nails or ceramic coated decking screws.
It comes with the nailing pattern printed with on the sheets.
Then a layer of 1/2 or 3/8" underlayment rated plywood making sure the seams do not line up with the subfloor below.

md2lgyk 10-02-2012 07:53 AM

What joecaption says. I used Advantec for the subflooring when I built my house. It is a very good product.

Jrhenry24 10-02-2012 10:19 AM

Advantech
 
Is it neccessary to rip out the 1/2". We are talking 300 square feet so that would amount to several hundreds of more dollars in costs, 12-15 additioanl sheets of playwood for underlaymwnt, additional nails, and manpower to saw out the old subfloor and add blocking to the sides where there are no joists. If i laid advantech or some plywood over the 1/2" subfloor would i ever notice a difference?

ddawg16 10-02-2012 11:01 AM

I can relate to your pain.....been there...done that.....

Heard the phrase "You learn by your mistakes"....that is why I am the guys above are so bloody smart....

If your ok with the added height of the floor and the obvious trimming of doors you will have to make...not to mention the likely 'steps' as you transition from one room to another...then, yea, leave down the 1/2 'plywood'.

But if your going through the expense of hardwood floors....might as well do it right.....especially if you don't want squeaking....

To answer some of your questions.....

I would use screws to attach the 3/4" plywood to your 1/2" plywood...I would use 2" screws and screw in on top of the floor joist...that will give you about 3/4" of screw into your joist and thus reduce the chances of squeaking.

Felt? I don't know the answer to that one.....

Glue? Only if you were going straight on top of floor joists.

BTW...little side note....I'm in the middle of a 2-story addition to my house (been working on it for a year already)....upstairs I used 1 1/8" T&G. At first I complained to the architect....he said "Do it, you will understand afterwards." I did it....I now understand. My existing house is 3/4".......and everything bounces.....upstairs? It's about like walking on concrete......I do understand...

So....the advice Joe is giving you is because "He understands"....We are lucky that Joe and others like him contrimbute here.

Nailbags 10-02-2012 04:22 PM

replace it with 3/4 TG Plywood stay away from that cheep OSB stuff.

Jrhenry24 10-03-2012 05:04 PM

I have only two doors that i am replacing anyways. Will i ever notice the difference if i lay 3/4 t&g over the 1/2 as opposed to ripping 1/2 out and replacing w advantech and an underlayment?

ddawg16 10-03-2012 05:07 PM

Quote:

Originally Posted by Jrhenry24 (Post 1023107)
I have only two doors that i am replacing anyways. Will i ever notice the difference if i lay 3/4 t&g over the 1/2 as opposed to ripping 1/2 out and replacing w advantech and an underlayment?

Have you ever had a car repainted? Did any of the previous 'imperfections' show up?

You might be ok....but then again....if not....makes for an expensive mistake.

Care to hear about my experience with not useing T&G plywood?

You won't find me not using it again for a floor.

Jrhenry24 10-04-2012 07:58 PM

Quote:

Originally Posted by ddawg16 (Post 1023108)
Have you ever had a car repainted? Did any of the previous 'imperfections' show up?

You might be ok....but then again....if not....makes for an expensive mistake.

Care to hear about my experience with not useing T&G plywood?

You won't find me not using it again for a floor.

yes, i would like to hear your experience. i have probably gotten told 4 different ways to go about this by four different professionals. is there anyone who has laid plywood over 1/2 without problems? this is what i was originally told to do

oh'mike 10-04-2012 08:57 PM

If the old 1/2" ply is sound and flat--you can leave it and add another layer in top---1/2" bc is plenty---I use 1/4" small crown staples--1 1/2" long about every 6 to 8 inches----

Plenty of subfloor for 3/4" tongue and groove oak----

You have to be practical and draw the line between "Absolutely Ideal" and 'what will work just fine"---1/2" on top will be 'Just fine"


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