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Old 03-30-2013, 04:19 PM   #1
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Replacing solid 2x8 joists with stiffer alternative possible?


I am slowly redoing my 2nd floor bathroom which is pretty small - 5' by 8' ( tile floor area will be 5'x5').

While investigating under the floor - found major problem with joist integrity. Permanent unloaded deflection due to water damage, 2.5" plumbing holes almost at center span... remedied with lots of shimming, subfloor patchworking by previous owner. Horrible mess.

Current joists = 2x8 solid @ 16oc - 12' span.

I want to replace the joists rather than sister them because ideally, I would like to get to stiffness approaching L/720.

But I cannot find any open web/engineered/steel alternatives that have the same depth as a 2x8. Other than LVL which seems pretty flexible, everything has a depth of 9+". I can and will reroute plumbing drains so they don't go through joists if necessary.

Any ideas on stiffer alternatives to 2x8 SPF? If so, where does a home owner get them if not at Lowes or Home Despot?

Thanks
Bob

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Old 03-30-2013, 04:31 PM   #2
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Replacing solid 2x8 joists with stiffer alternative possible?


Replace and double up, add more between the other joist, add a girder runing down the middle of the span with footers and block piers.
Without some pictures were all going to have to guess.

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Old 03-30-2013, 04:42 PM   #3
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Replacing solid 2x8 joists with stiffer alternative possible?


joe is spot on, reroute your plumbing and use double floor joists or install a beam under the middle of the existing joist spans with new columns/piers under the end of the beam.
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Old 03-30-2013, 05:51 PM   #4
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Replacing solid 2x8 joists with stiffer alternative possible?


Steel S shapes and W shapes are readily available at any steel fabrication shop. More costly than wood, and harder to work with, but they are available in depths as low as 4 inches for W shapes and 3 inches for S shapes. 6 inch deep and 7 inch deep shapes are also available.
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Old 03-30-2013, 08:13 PM   #5
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Replacing solid 2x8 joists with stiffer alternative possible?


Just to let you know, the correct location to place a hole in a joist is in the center, as it has very little effect on its strength, The top being in compression, and the bottom in tension. The middle is pretty much neutral. 12 feet is a considerable span for 2 x 8's at 16 inches O.C. though.
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Old 03-30-2013, 08:19 PM   #6
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Replacing solid 2x8 joists with stiffer alternative possible?


Change your spacing to 12".

Use douglas fir from your local real lumberyard.

Install solid wood blocking, 2 sets, spaced equally at about 4' from each end.
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Old 03-31-2013, 10:04 AM   #7
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Replacing solid 2x8 joists with stiffer alternative possible?


Bob - you mention a 'stiffness' of L/720. Presumably you refer to deflection.
If your present (allowable) deflection is L/360, you will need joists twice as stiff to reduce your deflection to L/720. This means doubled 2x8s, or halving the spacing (8" c/s instead of 16"c/s).
Another way is to stiffen 8" joists with steel strip (6"-7" deep) screwed to the sides. But as the steel is a lot stronger in stiffness than timber (all things being equal), you would need to work out a thickness and depth of plate to give you the deflection you require - really an SE's job - and probably not worth it for you.
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Old 03-31-2013, 10:11 AM   #8
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Replacing solid 2x8 joists with stiffer alternative possible?


a good article for deflection limits of floor framing for tile flooring http://www.structural101.com/Wood-Fr...-Flooring.html
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Old 03-31-2013, 02:23 PM   #9
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Replacing solid 2x8 joists with stiffer alternative possible?


Thanks for all the great responses. I have some investigation to do.
Has to be 12' span - no mid beam because of dining room below.

I like the idea of the 3-4" steel shapes because then I'd have room for lateral floor stiffening on top of them, plenty of room for non-commode plumbing and also a sunken tub - the one I am installing has no skirt now so that would work - interesting to think about. Gonna have to call around about the shapes and read up on the difficulties.

Thanks for the article - yep - trying to avoid the disappointment they discuss in there. If the steel shapes idea is just too involved, I may just have to sacrifice the stone idea and trade down to something more forgiving like ceramic. It just getting too crazy.

Thanks for the help people. If there is anything worth presenting in photos as things move along - I will definitely post them.

Bob
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Old 03-31-2013, 03:33 PM   #10
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Replacing solid 2x8 joists with stiffer alternative possible?


I like the steel option.....

If that does not work....consider a PSL beam or two....you can get those in the same height as a 2x8 and just about any width you want....makes for a really stiff beam....

One other thought.....maybe consider 1 1/8" T&G for the sub-floor along with what ever you use for floor joists......glued and screwed.....that is how I did my second floor....I wish I had used it on the 1st floor.....about par to walking on concrete....

BTW.....it's not as hard to replace those floor joists as it may look.....actually, it harder to take them out vs putting back in.....in my case, I just cut them down the middle and then did some serious work with a sledge hammer to peal them over on their sides.....

This was my bathroom after I took out the floor....a cracked shower pan also gave me about a 2.5" sag....

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Old 04-03-2013, 06:52 PM   #11
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Replacing solid 2x8 joists with stiffer alternative possible?


You can use the IBS2000 between your 2" x 8" joists. They will stiffen your floor and help with the rattling china. Check out this website and give them a call.
www.luxorcorp.com
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Old 04-03-2013, 06:57 PM   #12
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Replacing solid 2x8 joists with stiffer alternative possible?


Try the IBS2000 for your 2" x 8" Check out the video at www.luxorcorp.com


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