Hello all...noob here hoping that someone on the boards can help with a problem.

My house is new construction (purchased spec) with floors constructed from 3/4" OSB over 12" composite I-joists set 24" on center with no bracing. Though it meets code, there is significant deflection and "bounce" in the main floor...a 45lb dog trotting at the right pace has china rattling in the hutch. Fortunately, the basement is not yet finished, so I have easy access to the joists.

So, how do I stiffen up the floor? How does one go about blocking or sistering with composite I-joists? If this has been covered somewhere on the HGTV site or on another page, could someone provide a link?

Thanks in advance...

be good to know what the spans are for the I joists to see if they are properly sized to begin with...

But about the only way you can stiffen these floors at this point is to construct a center bearing wall or beam at the mid point of the span.

L-shaped basement, with steel I-beam separating the two sections, and the composite joists running the shortest span across each section. Longest span for the sections are 14' and 14'6" respectively...and I don't care to split the basement into four long, 7'-wide rooms.

Are you saying it is impossible to fit blocking or bracing after the fact with composite joists? There's no solution to stiffening this floor post-construction?

Ok.

Did some research for you. Don't know your I-Joist manufacturer but will presume TrusJoist and use their data.

You can see all the information I am about to convey at this link:

http://www.trusjoist.com/PDFFiles/2027.pdf

First, it appears that your I joist are undersized for the spans and on-center spacing.
11 7/8" (110) I joists at 24" on center can only span 14' maximum for 40psf floors with 20psf dead loads. (See Floor Span tables page 4 in above link) If this is your floor load criteria, your joists are severely undersized at worst or barely meet minimum loading at best for the spans and spacing.

Using 10psf dead load, you can span more than 15' with the 110 I joist, but if the floor sheathing is nailed only and not glued, then the effective span is reduced by 6".

The bottom line here is that your floor joists barely meet or do not meet standard load criteria for their size and spacing. It's no wonder the floors bounce.

If you see the footnote(1) in the span tables for 110 joist 24"oc at 40psf live and 20psf dead loading at L360, you will see also that these spans require at the very least "web stiffeners" where they do meet the span requirements.

For web stiffener size, placement, and fastening schedule see page 8 in the above link.

Note for web stiffening material: "Web stiffener material shall be PS1 or PS2 sheathing, face grain vertical."

The problem for you remains, however, that if these floor joists are undersized for the spans and loads as I suspect they are, even web stiffening will not resolve you problem, and supporting the floors from below with beams and posts or framed walls at mid span may be your only serious option to reinforcing these floors.

Without knowing what additional types of bearing loads may be present from upper stories on these floors, installing beams and posts or a framed wall at mid span may still be your only viable option here.

You got dealt a minimally compliant if not completely non-compliant floor system hand here regarding its ability to bear loads, and now need to make lemonade from the lemons.

It's obvious the builder just got by or maybe even didn't get by with his choice of floor framing, but to save some money he really just didn't care.

You're going to have to deal with his poor choices and the center beam may end up being your only option.

Hi Ken.

According to the APA-The Engineered Wood Association, you can stiffen an I-beam floor in several ways.

1. Add an additional layer of subflooring, glued and nailed.
2. Attaching a rigid ceiling to the joists in the basement (e.g. sheetrock) will help.
3. You can add solid blocking between joists. If the span is less 14', then one set of blocking in the middle of the span suffices. If the span is longer than 14', then divide the span into thirds, and place blocking at those points. Blocking can be made of 2x dimensional lumbar and should contact the webbing of the joist.
4. You can reinforce the joists by attaching a 19/32 or 23/32 inch thick structural panel (such as plywood) to both sides of the entire length of the joist, nailing and gluing the panels to the wood caps at the top & bottom of each joist.

Of course, you can always combine more than one method for added stability. (For example, adding bottom strapping perpendicularly to the joists, in addition to wood blocking, will significantly strengthen the floor.)

You can download a free PDF file from APA. Go to http://www.apawood.org, click on "Publications" in the left navigation bar, then click "Publications Search" at the bottom left. In the search window, type "Vibration Retrofit" (without the quotes), and limit the search to Title (see the check boxes below the search window).

Subfloor, ceiling or blocking will have minimal effect on deflection, and I believe any or all would be a waste of money and effort.

Even adding a "thick structural panel" to each side of the joists does not directly attack the cause of deflection, which is related mostly to the depth of the joists, although it will help a lot more than the other options, IF it is done right.

Since your joists are 24" on center, you can add additional joists between them, ending up with joists 12" on center. This could be easier and cheaper than adding "thick structural panels" for the full length of both sides of the existing joists, and there's less worry about the job being done right.

One option no-one has suggested is the Legal option. Ask for a special inspection from your jurisdiction's building inspection department to see if your house meets code requirements. It might not. If not sue the builder.

Even if the house meets minimum requirements you might look carefully at any and all advertisements and disclosures you received when you purchased the house to see if any indicate that the construction was anything other than bare minimal.

Get an estimate from a reputable contractor to add the addtional joists or bearing wall recommended above.

Then write a letter to the builder of your house and the real estate broker who listed the house and demand that the problem be fixed at their expense or you will sue. While you are actuallly writing the letter to these people you need to consider that in the event of a law suit you will be using the letter as evidence and a judge will be reading it too, so include in the letter ALL pertinent facts -- tell your story to the judge in the demand letter. I would also send copies of your demand letter to the state agencies that regulate building contractors and real estate brokers. Make sure that you indicate that you have done so in your letter.

Contractors and Brokers are licensed they do not like having the regulating agencies on their backs. Too many complaints and they can lose their licenses and their liveyhood.

If the actual cost of fixing your problem falls within or near the limits of your area's small claims court, if you do not get satisfaction file a suit yourself -- a lawyer will be too expensive, wanting at least 1/3 of anything you collect. If your claim is much larger than the small claims limits call your local bar association and find a lawyer who specializes in this type of action. You should be able to meet with the lawyer for a 1/2 hour review at no cost. Interview more than one lawyer if it appears you may have a case.

Good luck!

Hello all...thanks for the feedback so far...

David, the legal option is not an option. My lawyer (always have one on retainer) has already investigated the options you've suggested, and the second inspection has been done. The house does meet code, and there were no disclosures stating anything but minimal compliance. There are no grounds for a suit in this situation.

Therefore, all costs fall on me, and all work falls on me (there's no way I'm paying for the contractor).

So, David, since the legal option does not exist, do you have suggestions on how to fix this?

Probably the easiest and most effective way to increase the stiffness of the floor would be to add more joists, ending up with joists 12 inches on center. However, piping and wiring could make this more difficult.

I'd definitely at least add the web stiffeners that "homebild" mentioned, since they should be there in the first place. And that makes the claim that the floor framing meets code a little bit suspect...since the code for composite joists is essentially the manufacturer's requirements, and the web stiffeners are apparently required. But they will not totally solve your problem. They are required to prevent the webs from buckling under load, and have little to do with stiffness of the joist.

The next best step would be to add the "thick structural panels" the full length of both sides of the joists, installed in accordance with the link which "Paul Tortland" referenced. You can piece these panels around pipes and wires, eliminating that problem.

Good luck.

I don't think the web stiffeners would do anything significant. web stiffeners are basically designed to decrease the likelyhood that the web will collapse under load - the "stiffening" is in the vertical direction.

Obviously picking up the loads at the centers of the joists with a wall, or beam and posts would be the best solution by decreasing the span length. If you have the space/room to do this it would also be the fastest and easiest.

Second best would be adding more joists, but as has been noted pipes etc cause a problem.

Third in my opinion would be nailing or screwing, and definitely gluing panels to both sides of the joists. I'd use at least 3/4" plywood of a grade that has few voids in the interior layers such as "sturdifloor." The glue is the key here. You are trying in essence to change the joists from I beams to box beams which should be stiffer. Probably won't help much though. If you choose to do this be careful to follow guidelines on where and how you place the fasteners so that you do not weaken the joist plates.

http://www.apawood.org/pdfs/download_pdf.cfm?PDFFilename=managed/D720.pdf

A couple of the APA recommendations attempt to cure vibration by adding mass to the assembly, in the form of additional subfloor, or a ceiling below. See my discussion of this approach under "Bouncy Floor" elsewhere in this forum (in Framing).

As an experiment, you could pile the heaviest furniture you can reasonably gather into the center of the room, and see if that helps.

The maximum allowable deflection for a 15-foot span would be 0.375 inches if 1/480th of the span is used as a criterion, and certainly no more than 0.5 inches if 1/360th is used. This would be the case under full load of 40psf live and 10 psf dead loads. In actuality, such loads are seldom approached. My guess is that your joists are not deflecting anywhere near the permissible maximum, but simply flexing...and more mass could well cure the problem, by damping the vibrations.

I'm coming in a little late on this. I am a structural engr. in CT. Engineered joists have an inherent "bounce" problem because of their relative low mass. We never design using the manufacturer tables because of this. There are programs that give "bounce" ratings for engineered joist designs - TrusJoist has one.

Adding blocking, additional subfloor, heavy ceiling panels all add only little, if anything, to the stiffness.

Best methods are to add joists between the existing or adding beam/bearing wall below.
Easiest is usually adding bearing wall below. This assumes you have a 4" concrete basement slab bearing on good subgrade. The wall does not need to be in the center of the joists. A 2 x 6 wall will be better than a 2 x 4 wall because it will spread the load better on the slab (since no footing below wall). Can even frame doors in the wall, with headers above, to create closets or something useful. Brace the wall studs with sheetrock or blocking.

Hello. CT Engineer hit the nail on the proverbial head by suggesting a closet along the wall, built transverse to the direction of the I-joists. If the interior of the closet were two feet deep, as is normal for clothing on hangers, then the overall span of the floor joists above would be reduced by the two foot depth, plus the thickness of the framed wall. 14 feet from foundation wall to foundation wall becomes 11'8 1/2", if 2"x4" framing is used, or 11'6 1/2" if 2"x6" framing is used. The resulting closet could also house an entertainment center, library, or display shelving. Just make certain that the entire floor load is properly transferred to the basement slab, and well-distributed, with a full bearing plate on the floor, since the slab will only be 4" thick, and, therefore, unable to adequately handle a point load. If columns and headers are used, as, for example, for a series of arched openings parallel with your foundation wall, then the slab neeeds to be opened up wherever you intend on installing a column, and a proper concrete footing, approximately 2'x2'x2', poured into the earth below the slab, and allowed to cure about 2 weeks prior to imposing any load on the newly poured footings. It takes concrete about 28 days to fully cure, but, at 2 weeks, it will be better than 80% of its final compressive strength. Once you set your columns, the hole can be finished off to level with the slab, but leave a full perimeter control joint with an expansion strip in each area surrounding each column, so as not to propagate a stress crack in your floor. The series of arched openings could also, just as easily, go down the center of the basement, with the same construction as described above. Depending on the length of the basement, a steel beam transverse to the I-joists, with but one column at each end, or with a beam pocket in the foundation wall at one end and a column at the other, would have the same effect, in that the spans of the I-joists will have been shortened, thus effectively stiffening the floor. You will need a structural engineer to calculate your effective loads, and to specify an appropriate steel beam, if you elect this option.

quote:

Originally posted by kallhands:
Hello all...thanks for the feedback so far...

David, the legal option is not an option.

I have a question relating to the legality issue. When I brought up a similar issue with the builder, I was told that the flooring had been built according to the code.

Well, I purchased the house based on the model home, there was hardly any bounce associated with the floor in the model home. Is that a valid argument ? The bottom line is that when you buy a house, and when they claim that it confirms to the code, it is really an issue of usability of the dwelling.

I have similar bouncy floor issues and I am not very happy with my 1-month old purchase (all wooden floors, but bouncy!).

The home is under warranty - has anyone had any luck with builders fixing this issue? Upon eyeballing the home, I did not see any sign of the builder using any significant glue between the i-joist and the subfloor. WHat percentage does the glue application dampen the bounciness of the floor? Very little, 90% ? any ? Thanks for this very helpful thread.

The glue has only a small effect on stiffness.

A structure can easily conform to building codes and still be unsatisfactory. The building codes set forth a minimum standard, not necessarily the BEST standard.

It is the work of the designer of the home to make certain that the structure will perform properly. If the home was purchased from a builder, chances are he used "stock plans" from some company far removed from the area, and then there is a chance that he did not follow the plans exactly. This is why I always advise people to use a good architect, and have the home designed specifically for them. That way you have someone on YOUR side.

Bouncy floors are common in any structure when elements are pushed to their limits. Bounce is also different from deflection. If your floors sag noticeably, you have deflection, and once established, it is permanent. If your floors bounce, chances are the joists return to their original position once the load is removed,

You can check for deflection by measuring underneath the joists. Measure the height at the wall or support girder, and then measure the height at mid-span. The difference should be less than 1/360 of the span, and in better structures 1/480.

You will probably find that there is much less deflection than that, because maximum floor loads rarely occur.

But if you observe the bottoms of the joists when a heavier adult walks across the floor above, you may notice some movement, but the joists will probably return to their original position

You will find more discussions of bouncy floors elsewhere in this forum. There may not be any cure that you would like, sorry to say.

Thanks for the info. If a builder displays a model home that has no similar flaws, as a "dumb" buyer, it appears that it is the responsibility of the builder to confirm to these issues. I mean, if true, is it perfectly acceptable for a builder to exceed building code in the model home and not do the same when the actual dwelling is constructed.

Secondly, what happens if the floor is not level ? I am assuming that if the floor is not reasonably level, we will experience more bounciness ?

I also noticed that the model home had solid tile in the kitchen area, and carpet with good padding in the family room area. We have wooden floors (strips) everywhere. I wonder if the bouncing effect is more pronounced when having wooden floors ?

This message has been edited. Last edited by: anonymouse,

It should be easy to investigate. Just check joist sizes and spans in the model, compared to your house. But the model home is probably not referred to in your contract, so there is no reason to believe that any differences between the model home and yours will result in an actionable situation.

Read your contract and see what it says. If it refers to the building code as a standard, then the builder obviously hoped that his customers would assume that would mean a sound house. Sadly, that is far from the truth.

The floor finish would have very little to do with bounce. It is strictly a matter of joist type and joist depth. And as I said, a joist can meet or even exceed code minimums and still exhibit bounce.

Moral: builders should not design homes, and buyers should not allow them to. A good architect would have been money well spent. I am constantly amazed that buyers skip this vital step, and then run into problems such as yours. And others read about the problems, and then go ahead and do it the same way. often with the same result.

Interestingly, I visited the model home today. It has tile floors in the kitchen, it does bounce, although a lot less than ours.

I went into the basement and noticed that the subfloor has been glued to the i-joists in addition to nails, I see no trace of glue whatsoever on my subfloors. I also noticed that some of the i-joists do not even sit snugly on the metal i-beam. I wonder if this is contributing to the problems I am having. If that is not the case, why then does the model home feel stiffer compared to my home (I dont see any differences, unless there are 2 layers of subfloor in there!).

Hello all...sorry about the long span between posts on this.

Anonymouse, I noticed the same thing when I went back to the model, but there wee more differences. First, the model was completed with their basement finishing option. The extra construction in the basement probably added to the rigidity, combined with the fact that they could have additional joists above the ceiling drywall.

I hired a local builder (recommended by the city inspector) for a 4-hour design session, with an up-front fee and the understanding that I would be working with him in the future for any work beyond my capabilities.

Together, we came up with a solution that has worked well. After making exploratory cuts in the foundation, we found we had enough thickness to support a load-bearing wall (as per W.J. Parker's suggestion). This wall was built 21" out from the outer wall, making an 18"-deep wall of storage closeting.

In the openings where lack of HVAC ducting allowed, we went to joists 12"-on-center, spanning from the steel I-beam to the new wall. Everywhere this couldn't be done, we blocked the top and bottom of the I-joists with 2X4 sections tightly fitted between.

The result has been a significantly stiffer and quieter floor, quite a bit of hassle, time, expense and a lesson never to buy a spec unit again.