Subject: Re: [Shop-talk] Floor repair

From: Brian Kemp <[email-masked]>
Date: Tue, 8 Dec 2015 20:20:34 -0800

Bob - Is there any damage to the wood?  I'd wonder about the reason it 
got spongy.

A bigger sheet will be stronger, but you can make due with a smaller 
patch.  If you cut out the damaged section, I would leave the existing 
floor over the full joist to maintain the strength of the rest of the 
floor.  I would then take additional 2x boards and sister them to the 
existing joists to attach the patch.  This will give you a full 2x to 
attach the floor patch, so you don't have to screw right at the edge of 
the plywood.  I would also add 2x blocking between the joists where you 
cut to support the edges of both the original floor and the patch.  That 
will also stiffen the floor.  If the patch is more than a couple feet or 
you have a heavy load at that location, I would also add blocking in the 
middle.  It is only an one extra length of board when you are going 
through the effort.

If the wood is not damaged and you have access to the floor joists from 
below, like an unfinished basement or a crawl space, I'd just add 
blocking from below.  Push the blocking up tight and screw it in and you 
don't have to mess with the floor.

If this is due to water damage or termites, expect the problem to be 
bigger than it appears before demo.

Brian

On 12/8/2015 6:11 PM, Robert nogueira wrote:
> I've got a little section of a floor which is spongy. The floor is 3/4"
> plywood with a over lay of 1/4" plywood all on 16 inch centers.  The bad
> section is small and only between two joists. My plan was to cut out the bad
> section between the joists and replace it with new plywood. My question, is
> plywood stiffer between two joists  if a sheet spans several joists or will my
> plan of one piece spanning between two joists be as stiff as a full sheet
> spanning several joists?
> Also, is plywood stiffer across its width or stiffer across its length
> I hope this all makes sense .
> Bob
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From: "Peter J. Thomas" <[email-masked]>
Date: Wed, 9 Dec 2015 09:50:54 -0500

> I hope this all makes sense .
I prefer to span at least three joints, it basically doubles the 
stiffness.  Adding 2x4 cross bridging between joints also helps.

Plywood is slightly stiffer along the length, but only slightly.
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From: Jim Juhas <[email-masked]>
Date: Wed, 9 Dec 2015 10:04:55 -0500

I have done this with extra blocking as Brian suggests. 2x4 was plenty to
provide additional support. I was replacing water damaged plywood under my
bathroom.

Sent from my iPhone

> On Dec 8, 2015, at 9:11 PM, Robert nogueira <[email-masked]> wrote:
>
> Unsubscribe/Manage:
http://autox.team.net/mailman/options/shop-talk/[email-masked]
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From: "Pat Horne" <[email-masked]>
Date: Wed, 9 Dec 2015 09:10:56 -0600

Bob,

You can just replace the spongy part, but it would be better to replace a
bigger area. If I were doing it, I would cut out a section about half way
between the joist and the next one on each side. With your joists on 16"
centers, the patch would be about 32" wide. This makes for stronger support
of the area. I would also screw 2x4's around all the edges of the opening,
half under the old wood and half to support the new. Use adhesive and screws
to secure it.

While you have the floor open look to see what might have caused the wood to
fail in the first place. Is the location under or near the frig? There may
be a leak there. There may be a duct under the floor that could be leaking
moist air in that area. Plywood doesn't usually fail like that by itself.

Peace,
Pat

-----Original Message-----
From: Shop-talk [mailto:[email-masked]] On Behalf Of
Robert nogueira
Sent: Tuesday, December 08, 2015 8:12 PM
To: Shop Talk
Subject: [Shop-talk] Floor repair

I've got a little section of a floor which is spongy. The floor is 3/4"
plywood with a over lay of 1/4" plywood all on 16 inch centers.  The bad
section is small and only between two joists. My plan was to cut out the bad
section between the joists and replace it with new plywood. My question, is
plywood stiffer between two joists  if a sheet spans several joists or will
my plan of one piece spanning between two joists be as stiff as a full sheet
spanning several joists?
Also, is plywood stiffer across its width or stiffer across its length I
hope this all makes sense .
Bob
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Archive: http://www.team.net/archive
http://autox.team.net/mailman/options/shop-talk/[email-masked]
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