Hi,
I just moved into my new house. The floors have annoying vibration when walking normally across a room. The whole first floor is either hardwood or ceramic tile.
The subfloor is Avantech 3/4″. The hardwood is 2 1/4 x 3/4″ strip flooring, nailed to the subfloor(stapled actually).
Does anyone have any ideas how to solve the vibration problem. The floor joists are Trus Joists (16″ oc) and the beams supporting the floor are LVL’s.
The joists are not reinforced with any type of blocking like they normally do when 2×10 dimensional lumber is used for the joists. According to the builder the cross bracing is unnecessary.
Would cross bracing the joists help with the vibration problem? Does anyone have any other ideas? Thanks….
Kathy
Replies
I would believe your builder is wrong on the cross bracing. I know that we cross brace anything that is conventional joists on the jobs that we do. I can't believe that this would not help your vibration problem. Its is hard to cross brace some areas due to duct work and plumbing, and lot times it gets ripped out. I would suggest to your builder that he put some cross bracing in.
We cross brace any floor joist spanning more than 8 ft. for the sole reason that it doesn't have much of an impact on budget. It can usually be done with jobsite scraps - solid bridging/blocking or cross bracing. If the architect, building inspector or manufacturer specifications didn't suggest any of these methods than offer to pay your builder for this extra service.
Mostly Questions................................................
What depth are the I-joist? ( 9-7/8" or 11-7/8" or 14" )
What is the composition and size of the top & bottom flange?
What is the span of the joist?
What is the configuration of the LVL beams? Length of span +number & size of LVL.
What is the loading of the I-joist on the LVL beams?
Are ther any load bearing walls on the joists or beams?
A drawing would be helpful.
Most I-joist manufacturers do not spec blocking/bracing if intalled as per details,
BUT there are ways to use bracing and bottom flange banding to couteract
"bounciness".
Hopefully the info from the above questions will lead us to options to help.
...........................Iron Helix
I am going to try and get a copy of the drawing from the builder showing the floor system so I don't have to measure everything.
Depth of the joist is 11 7/8"
Top and Bottom flange are engineered lumber.
Span is approximately 17.5 ' to either an LVL or to the edge of the basement wall. I measured but will try to get a drawing from the builder or draw one.
The LVL's are 9 1/4" wide with 3 in parallel. One LVL on the south side is approx. 24' long, the next LVL in parallel to it but offset since the house is not symmetrical.
Loading of the I-Joists on the beams is the joists sit on top of the LVL's.
One load bearing wall on the LVL in the (approx) middle of the first floor. Need drawing to be explicit.
Thank you...I will get the drawing today.
You mentioned that one of the LVLs is 24' long. But you don't mention the distance between the poles. That would be helpful to know.
The 17.5' span between supports is well within the norm for 11 7/8" I-joists. I'll be curious to see some more details if you can come up with them.
If the joist layout was done in a computer program, several of us here have autocad and related programs. If you could get a copy of that you can attach it to a post.
Or if you have one on paper, I'll email you my fax number if you'd be willing to send it to me. Why do you press harder on the buttons of a remote control when you know the batteries are dead?
Iron Helix is right on in asking for more info. The span of the I-joists is important. And the span of the LVL beam, from post to post. (or other support)
When he asks about the "loading" of the I-joist on the LVL beams, he means do they sit on TOP of the beam, or are they hanging on the SIDE of the beam with hangers.
He is also correct in saying that I-joists manufacturers don't recommend cross bracing.
Do you have access to the I-joists from underneath? Are you on a basement or crawlspace?
Exaggeration is a million times worse than understatement
Hi Boss, Looks like we were tyuping at the same time. I knew you'd be finding this one..
Excellence is its own reward!
The I-Joists are in the basement.
For a definite, objective opinion, I need the same info that Iron outlined for you.
But as a generic answeer, some of the I-joist companies recommend, based on studies, that the simplest improvement can be found in adding strappping to the bottom of the I-joists at 16"oc.
I suspect that you will find Boss Hog weigh in here with a link to an article on vibration for you as it is one of his hot buttons.
one of the problems is that I-joists are designed for load without concern for vibration. I believe that the lower mass of the I-joist construction contributes to vibration as opposed to solid frame lumber. I still prefer the I-joist system but like to plan with extra depth.
Another thing to consider, since you mention LVL support beams is that if you have a center beam, with LVLs spanning across it, depressing the floor on one side of it can create an uplift bounce on the other side, and that wave action can replay itself, sometimes multiplying effects felt.
The builder is wrong that nothing can be done. But he is not substandard. Understanding of wave action and vibration is only beginning to be brought out in the last few years as I-joists make this phenomenon more common.
Excellence is its own reward!
easy cheap test.
get a piece of 2x4 or 2x6 say 10 ft long.
run it under the floor across the beams, use square head ss screws.
i tried that under my washer and it worked great - stopped all the harmonic vibration.
easy
cheap
Just wondering, do square head screws impede vibration better than phillips or torx head screws?
;).
Excellence is its own reward!
not that i know of
I am not good at hammering nails while laying on my back so a cordless drill and (square drive) screws were easier for me.
Edited 5/18/2003 12:15:04 PM ET by wain
TJIs are strong, but their low mass makes them susceptible to the problem that you describe.
The manufacturer recognizes the problem and recommends 1-by-4 strapping attached to the bottoms of the flanges, with the strapping run perpendicular to the TJIs. Nail the strapping to each TJI flange with two 8d nails. Don't cross-nail. Run the strapping every 8' on center.
It's a low-cost fix. Low materials cost, with just a few manhours required.
Priint out the following link and hand it to your builder. If he uses engineered products often he should incorporate more of these ideas into the up-front installation to prevent future problems.
http://ki-lumber.com/engineered/TJI/2065.pdf
I believe you copied the wrong link. The field guide is for the prevention and repair of squeaks. They already fixed the squeaks....now it vibrates or at least the vibration doesn't dampen out quickly enough so it's very noticeable.....thank you anyway...I will search the trus joist web site for other field guides....
Read the bullet right below Figure 22.
I think the replies to this post are a great example of "what is Fine Homebuilding?"...that's not a mistake, it's rustic
Ah...I see it ....thanks...