# Bouncy ceiling in soon-to-be finished basement



## pburgh19 (Nov 23, 2015)

I'm working my way through finishing my basement and I've come to another point where I need a few opinions. Our floor plan results in the main room of our basement being directly under our great room on the main level. Our kids tend to bounce around a lot up there (as well as my wife when she works out). While in the basement, I can SEE the floor flexing downward as people jump around upstairs. Once the basement is done all that activity should be downstairs... but I'm concerned about how that flex could affect the basement ceiling once drywalled. 

The basement room is roughly 14.5' wide by 30' long. The flex point is about 10 feet off one end of the room.  I could install a support column, but it would get in the way of the kitchen(ette) that's going in at that end. 

Will the drywall joints crack with that flex? I am running furring/strapping, fyi.

Thanks


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## Bud9051 (Nov 11, 2015)

What size are the floor joists above?
Were cross braces installed or solid blocking?
Basically, yes the drywall will crack if the ceiling bounces. Some of the drywall pros may have some advice to improve that situation.

For disclosure, I hate basements. Sorry, but I've seen too many massive projects turn to poo for many reasons. Based upon my dislike I usually advise many careful steps for those wanting to utilize that extra space. I won't force the advice upon you, but it is available if you ask.

My specialty is now energy efficiency, but I have been a small contractor for years.

Bud


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## pburgh19 (Nov 23, 2015)

The joists are 2x10. There are a few blocks, but mostly cross-bracing. 

I'm fairly certain I could stabilize the area with a column, was just wondering if that was going to be a requirement. :|


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## Bud9051 (Nov 11, 2015)

I would assume you would like to avoid an extra column in the basement. A little complicated, but sistering some engineered lumber (LVL beams) with a few of those 2x10s would sure make an improvement. A lot depends upon what is in those cavities now.

More blocking and cross bracing will help make the floor move as an assembly as opposed to individual 2x10s flexing down by themselves. From my experience, blocking is never taken very seriously when installed.

Bud


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## pburgh19 (Nov 23, 2015)

I had considered sistering as well. The cavities in question are empty, thankfully. If sistering, do the engineered beams need to run the entire width, or can they be ~80% wide and still provide the necessary support?

If I did have to go the column route... I could probably turn the kitchette in to a bar and hide the column in there somewhere. Not my first choice, of course.


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## Bud9051 (Nov 11, 2015)

You said the basement room is 14.5 x 30 so I assume the 14.5 is from a center beam to the outside wall. If by 80% do you mean 80% of the 28' (or whatever) full width? Or 80% of the 14.5'.

If just the 14.5' it would still make a fifference but obviously not as much as going the full, center to outside.

I hope that makes sense.

Bud


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## pburgh19 (Nov 23, 2015)

I was referring to the 14.5 width. The joists run across the room.


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## Bud9051 (Nov 11, 2015)

If you are not dealing with a lot of wires, pipes, and ducts, then sliding a 15' board in there should be possible. But the majority of the flexing would be coming nearer to the middle of the span, so 80% that covers the middle should be an improvement.

Bud


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## Gary in WA (Mar 11, 2009)

If you solid block the mid-span expect a 66% improvement on stiffness over x-bridging alone; and add (in addition) a 1x4 furring there (to joist bottoms), expect a 167% improvement over x-bridging.

Gary


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