Steel joists - bouncy

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Topic by TipTop posted 02-16-2015 04:45 AM 3250 views 0 times favorited 4 replies Add to Favorites Watch
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1 post in 4241 days

02-16-2015 04:45 AM

My two story house is steel-framed. The flooring system throughout the home is such that even a child causes the floors to deflect when walking across any room. This phenomenon has been annoying me for many years. When the kids play in the house, it seems like the whole house rumbles (it doesn’t but when in the room directly below where the kids are, it’s very loud). An adult walking across the floor causes enough deflection to shake floor lamps, enteraintment center and the like.

All I can tell you about the steel floor joists is that they are 24” on center. I have no idea what the gauge is. The joists are “C”-shaped. There is no “blocking” between the joists. Perhaps this can’t be done with steel joists, I don’t know.

One contractor tried this solution for the main level flooring (from the previously unfinished basement): he ran wood joists along side the steel joists before he installed the drywall. Then we removed the carpeting and installed thick hardwood flooring. While this helped a little, I was surprised to find the floors were still bouncy.

I was hoping we could find a solution without tearing out drywall for the rest of the floors…meaning I was hoping to find a solution that would involve going through the subfloor (most of the floors are covered by carpet which we want to replace anyway).

Any insight would be greatly appreciated.


View UnionLabel's profile


70 posts in 4399 days

06-14-2010 03:58 PM

At 24” on center, what is the span? What are the dimensions of the “C” shaped beams? Is the basement open concept? When was the house built? Is it prefab, modular, or site built stick style construction? Pictures would be helpful.

-- Methods are many,Principles are few.Methods change often,Principles never do.

View Catspaw's profile


35 posts in 5025 days

06-15-2010 12:41 PM

It’s my opinion that you’re SOL. The floor joists are doing exactly what they “do”. They flex (which is why skyscrapers don’t fall over in high winds and bridges don’t collapse under weight.)

It’s the old adage about the mighty oak and the willow. I’m guessing that only a shorter span and narrower o.c. would suffice. That is, short of sistering on wood joists to stiffen them all up.

I’ve read where bridging does nothing to add to the strength of a floor system. However, I would be curious about screwing plywood to the bottom surface that would create a torque box. Torque boxes are notoriously stiff. The second skin, I beleive, is what completes the system to stiffen it (as opposed to just having the joist and the subfloor on the upper surface.

I suppose a relatively cheap experiment could be to add a ton of screws thru the subfloor. A bi-metalic strip has added strength and does not want to flex. It could be that the subfloor fasteners are giving way slightly, allowing the two materials to flex slip and flex (assuming no subfloor adhesive was used.) Adding screws might tend to minimize the slop between the joist and subfloor.

I kind of notice the same thing with wood floor trusses (the 2×3 with OSB web between type.) They are strong, but, it always feels like you’re walking on the head of a drum. Normal joists always seem to have a damping effect on that bounce.

-- arborial reconfiguration specialist

View UnionLabel's profile


70 posts in 4399 days

06-15-2010 02:18 PM

Check out page twelve. There are stiffeners that twist in place. BOCA code requires a minimum of 3/4” T&G plywood over steel, with #8 bugle head screws every 12” to be installed or flanged steel pin to be shot in every 12” also.
There are a number of articles regarding mis-installation of subfloor materials or wrong thickness. If the subfloor is 3/4”, then it is possible that there were joist clips missed to stiffen the joists. The principle is the same as boxing in a channel frame on a car in order to stiffen it.

-- Methods are many,Principles are few.Methods change often,Principles never do.

View michellejohn's profile


19 posts in 991 days

09-25-2019 07:13 AM

The selection of the steel joists depends on the structure that we are trying to build. There are some varieties of option click to read more available to handle different situations. The use of this joists reduce the overall building height and help to save the additional costs.

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