Support Beam for spongy floor.

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  #1  
Old 10-28-18, 06:17 PM
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Support Beam for spongy floor.

Hello,

Iím trying to put a beam in to brace the floor in my Family Room. The room is 15 feet wide and I feel a little sponginess. My plan is to build my own beam (24 ft long) using maybe 2- 2x10ís sandwiching plywood in between. Iíll use jack posts for the support.
The floor joists are exact measurement- 2Ēx9Ē.
Questions:

Would it suffice to use 3 jack posts? One on each end and one in the middle?

Would the Jack posts being 12 feet apart be enough to take the sponginess out of the floor?
Also, what type of wood (Doug Fur)?

Thanks for any input...
 

Last edited by joeponcho; 10-28-18 at 06:32 PM. Reason: Add info
  #2  
Old 10-28-18, 10:27 PM
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Better to build small walls, which are permanent, under the ends of your beam than jackposts, which are meant to be temporary.
 
  #3  
Old 10-29-18, 04:13 AM
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There was a 12'x14' addition built onto my living rm before I bought the place. For whatever reason they ran the joists the long direction which resulted in a slight give when walking across the floor. I used two 2x6 [beam] supported every 6' in the crawlspace. That was about 25 yrs ago and the floor has been solid ever since.

I assume you have a basement under the family rm. How is that space used? I like SS's suggestion for walls to support the beam.
 
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Old 10-29-18, 05:38 AM
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So, this is similar to what I have done to several of our homes where there was same soft flooring.

Typ I would buy a small glue lam but making one is acceptable. In all cases I also used adjustable posts and results were great, rock solid floors. I also screwed the beam to each joist which helps also!

Remember, these are not load bearing all they are doing is stiffening up the floors to eliminate the deflection that occurs when someone walks on the floor, minimal load!

With my glue lam I have some areas that were probably 15' span, with the 2x10 construction the 12 should be fine!
 
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Old 11-02-18, 12:33 PM
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Thanks for the info. After researching for the past week, I think I'm going to use either
3- 2x10's or 3- 2x8's and support them with Jack posts every 8 feet. Since this is not weight bearing, would 3- 2x8's suffice supported every 8 feet?

For some reason the previous owner put in 1 jack post with 3- 2x8's sandwiched together but they're only 4 feet long.

Is there a big difference between 3- 2x8's & 3- 2x10's?
 
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Old 11-02-18, 12:39 PM
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The 2x10 will always be stiffer but remember the load that these are supporting is nothing more than the weight of someone walking on the floor so a couple of 2x6 would be sufficient,
 
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Old 11-02-18, 12:50 PM
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Thanks Marq1.
So 3- 2x8's would be above and beyond, correct? I tend to over do things!
 
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Old 11-02-18, 04:26 PM
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fyi, the straps on the posts fit best with 2 - 2x? so give that a consideration.
 
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Old 11-02-18, 05:47 PM
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Remember, these are not load bearing
It doesn't happen often, but I'm going to disagree with Marq on this - if the beam(s) is/are not weight bearing, then nothing would be accomplished. Additionally, temporary supports tend to raise more questions when a potential buyer is sought.
 
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Old 11-02-18, 07:35 PM
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Thanks stickshift. Iím confused though. Youíre not the only person to say that these Jack Posts are temporary, yet I see them in just about every basement Iíve been in that was built after the 1960ís. What do you consider a ďPermanent Post?Ē
 
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Old 11-02-18, 07:57 PM
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Also, Iím researching ďPermanent Jack PostsĒ and what does this statement mean: ďCan be used permanently if as a secondary support.Ē Itís a contradiction in terms, isnít it?
 
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Old 11-03-18, 04:52 AM
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You’re not the only person to say that these Jack Posts are temporary, yet I see them in just about every basement I’ve been in that was built after the 1960’s.
They are quite common but usually the ones used during construction are embedded in the concrete which signifies they are part of the building design. When they are set over the concrete it's generally an indication they were added at some point to fix an issue - which leads a potential buyer to question what else might have been built wrong. Jack posts are supposed to have a footer underneath them although it's not really needed in your situation.
 
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Old 11-03-18, 06:27 AM
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Well there really is no other way to fix what you are trying to do other than adding additional support, every house I have done this to, at least 3 that I can recall then had the basement finished afterwards. so the beams and posts were then inside walls so they were not visible.

Would it raise questions, maybe but then you have to live with the soft floors or take them down before selling,

I also always used the solid posts, not the really cheap adjustable ones although for the loads you are applying, the weight of a person and the beam itself, it would be more than sufficient!

https://www.doityourself.com/forum/a...1&d=1541248005
 
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