What underlayment needed for 3/4" hardwood floor?


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Old 08-05-16, 07:55 AM
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What underlayment needed for 3/4" hardwood floor?

Hi,

i'm going to lay hardwood floor for a big room above my garage. So I need something that has insulation effect to keep the room slightly warmer.

I googled around seeing something like Selitac stuff on Ebay but it sounds like it's for laminate floor. Some cork or rubber stuff too, which might be too thick. The height of the room is 8' and it's not high enough and I don't want too thick floor to make the height smaller.

What would you think?

Thanks in advance.
 
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Old 08-05-16, 08:15 AM
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You want insulation but no change in height? Not going to happen. That said, the best thing you can do now is air seal between the garage and the bonus room.
 
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Old 08-05-16, 08:19 AM
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Is the garage ceiling finished now? If so, is it insulated? The garage should be air sealed and have a fire rated finish. If it is finished but not insulated you could blow in fiberglass or foam it.
 
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Old 08-05-16, 09:03 AM
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As others said, under the floor is the best place to insulate. Foam will give you the best R-value and will air seal the entire floor.
 
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Old 08-05-16, 09:51 AM
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Forgot to mention....cellulose can be blown in too.
 
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Old 08-05-16, 02:48 PM
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What type of floor? Nail down, floating, click lock? Underlayments for floating floors are for sound deadening and not for insulation. They may act as a moisture barrier but that is about it. Nail down would use 15# roof felt paper.
 
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Old 08-05-16, 05:30 PM
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Thanks for the quick return from you guys!

Yes, the garage ceiling is of sheet rock, above which is fiber glass insulation (but not thick enough, I can see there is some room to be filled out with more layers of fiber glass insulation, not sure if blown foam is fine). It's hard to lay more f.g.insulation on top of the existing one since I need to remove the sub-floor first, or I'll have to get rid of the sheet rock ceiling.

The floor to be laid is 3/4" hardwood, which will be nailed on top of sub-floor with underlayment in between.

Another question. Can I blow/spray foam under the sub-floor with the existing insulation in there? There is a room next to the garage. If I take off the drop-ceiling of the room, I can see what's above the garage ceiling (insulation between the joists). Maybe I can blow foam through the openings.

Thanks again.
 
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Old 08-05-16, 05:49 PM
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OK, you can talk to others about additional insulation between the joists, but top side for nail down you need the following: Minimum 5/8" plywod or minimum 3/4" OSB. 15# felt paper under the hardwood and use the longest cleats you can get. It is for holding power. Also, take the time to screw the existing subfloor down using appropriate length deck screws.
 
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Old 08-08-16, 06:06 AM
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The right sized sub-floor is already there. I reinforced the sub-floor by 2 1/2" ring-shank nails. Are you saying it must be deck screws? Of course, ring-shank nails won't be as good as screws. I can certainly redo it if screws are way better.

You said longest 'cleats'. Are you talking about the floor nails? Please advise!

As for the underlayment, what you recommended is sort of thinner than the following?

Flooring Underlayment 1 8" 4'X125' Under Hardwood LVT Laminate w Tape ESP Low E | eBay

Thanks czizzi for your info.
 
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Old 08-08-16, 03:50 PM
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Cleats are nails for flooring (or you use staples).

That is a lot of money for underlayment for a nail down floor over an already insulated floor system. 15# felt => $20 Not seeing the benefits. Underneath is unheated space. Heat rises so the heat loss would be in the ceiling in the FROG. Wood is a poor conductor of heat, so I don't see a need for a radiant barrier.
 
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Old 08-09-16, 04:18 PM
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OK, forget about the reflective foam underlayment and i will follow what you recommended.

The cleats that I got is of 2" nails from Bostitch. I did not see 2 and half inch ones at Home Depot. Is that OK? I bought 2 1/2" Dackmate nails today to reinforce the sub-floor.

Thanks for your advice.
 
 

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