# Putting subfloor in my attic



## buletbob (May 9, 2008)

your best would be to use 3/4". I have seen 1/2" & 5/8" used. a brad gun would be the wrong choice. why not screws. this way you can remove the sheet with out popping any nails in the ceiling. BOB


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## Speedball (Nov 2, 2008)

I second the 3/4" so it won't bow with weight on it and screws are a great idea for removal if ever needed.


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## MrBill_DIY (May 4, 2008)

*Attic Subfloor*

I had a contractor do this to my attic floor last summer. He just brought in 4'x4' sheets of 3/4" plywood and screwed them down with drywall screws, which have deep threads and thin heads that don't need countersinking. It worked fine, and now I can unscrew the pieces easily.


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## 4just1don (Jun 13, 2008)

I would NOT use drywall screws but use construction screws instead,,,torx heads are easiest and most non stripping,,,"I" hate phillips heads,course my hands hates screwing anyway,,,cause of worst one of those 'ritis' brothers,,,aurthur


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## bjbatlanta (Jul 16, 2008)

Gotta agree with the screws just for the sake of not causing drywall problems below from the impact of a nail gun. You'd need to use a framing gun with 6d or 8d headed nails.


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## chad4290 (Nov 28, 2008)

use .113 diameter w/ two 3/8 ring shanked nails with pl400 subfloor adhesive. don't want squeaks


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## Wildie (Jul 23, 2008)

My vote would be 5/8" t/g plywood sheeting screwed down with Robertson (square head) deck screws.[ if the ceiling joists are 16" o/c.- 3/4" ply, if 24" o/c]

Drywall screws are no good for decking, as their fine threads will allow them to pull out.


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## AllanJ (Nov 24, 2007)

>>> Drywall screws are no good -- fine threads

I have seen "fine thread drywall screws" for metal studs. But more commonly (where I live) I see "coarse thread drywall screws" for wood studs and these are mighty difficult to pull out of wood.


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## Wildie (Jul 23, 2008)

AllanJ said:


> >>> Drywall screws are no good -- fine threads
> 
> I have seen "fine thread drywall screws" for metal studs. But more commonly (where I live) I see "coarse thread drywall screws" for wood studs and these are mighty difficult to pull out of wood.


 I know what you are saying! I just prefer drywall screws for walls and deck screws for decking!

At risk of hijacking the thread, has anybody ever seen square head drywall screws?


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## MrBill_DIY (May 4, 2008)

I assumed that the screws I see in my attic floor are drywall screws, but maybe they are actually deck screws. In looking at deck screws, I can hardly tell the difference between coarse thread drywall screws and some deck screws, since they both have thin heads and very deep threads. The threads of coarse thread drywalls are very sharp and allow the screws to go into wood easily with no pre-drilling, and the head seats into the surface so there's no countersinking needed. In spots where I thought the floor needed some a few more screws I added some coarse thread drywall screws because I already had some, and they worked fine. They will not pull out easily because the threads are very wide. But they may not be as strong as deck screws even if they are shaped the same, so I would probably use deck screws if I were doing the job from scratch.


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## Termite (Apr 13, 2008)

Minimum 5/8" plywood and deck screws (not drywall screws). 

Are your ceiling joists sized for use as a floor and not just as a ceiling? I'd be concerned about using the area above as a floor if you don't have adequate framing to support the live and dead loads of a floor. Most ceilings are not sized to do that.


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## Wildie (Jul 23, 2008)

MrBill_DIY said:


> I assumed that the screws I see in my attic floor are drywall screws, but maybe they are actually deck screws. In looking at deck screws, I can hardly tell the difference between coarse thread drywall screws and some deck screws, since they both have thin heads and very deep threads. The threads of coarse thread drywalls are very sharp and allow the screws to go into wood easily with no pre-drilling, and the head seats into the surface so there's no countersinking needed. In spots where I thought the floor needed some a few more screws I added some coarse thread drywall screws because I already had some, and they worked fine. They will not pull out easily because the threads are very wide. But they may not be as strong as deck screws even if they are shaped the same, so I would probably use deck screws if I were doing the job from scratch.


 When it gets right down to it, the screw length is more important.


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## gma2rjc (Nov 21, 2008)

I'm wondering if you have insulation in your attic and, if so, is the subfloor compressing it?


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## MrBill_DIY (May 4, 2008)

*Insulation*

I already had blown-in cellulose insulation in the attic floor, before replacing the thin plywood that was the old attic floor with thicker plywood. So the old blown-in insulation is still in the floor. Also, I had a contractor insulate the attic rafters with fiberglass to reduce the temperature extremes in the attic. I got that idea from a neighbor who did the same, and it seems to have helped since the highest temperature I recorded up there last summer was only 88 degrees.


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## 47_47 (Sep 11, 2007)

Wildie said:


> At risk of hijacking the thread, has anybody ever seen square head drywall screws?


Try McFeelys

http://www.mcfeelys.com/drywall-screws


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## Wildie (Jul 23, 2008)

47_47 said:


> Try McFeelys
> 
> http://www.mcfeelys.com/drywall-screws


 They seem to have em all! (smile)


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## Marvin Gardens (Sep 30, 2008)

Before you go ahead with the floor make sure that the joists will handle the weight. I have been seeing way to many attic conversions lately that don't have big enough joists to handle the load. I get called in to do minor repairs like fix cracked drywall and spongy floors.

Once I look at the overall picture I see that they have to big a span for the weight they are carrying.


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