Building and Construction - TJI Joist 110 11-7/8 inches PROBLEM

Author

TJI Joist 110 11-7/8 inches PROBLEM

Xeroid

2005-10-20, 3:21 pm

I contacted the manufacturer of this joist before install. They told
me it was the right residental joist I needed for my floor spanning
about 17' 6". They told me I could space them either at 16 inches with
bracing or on 12" centers without bracing. I installed them on 12"
centers. 5/8 TG Plywood is screwed into place as the sub floor.

PROBLEM ... the floor is way to bouncy. One man walking on the floor
can feel it .... and if you are underneath you can see the joist move!
Deflect downward! Maybe up to an inch ?

I contact the manufacturer again .. now they tell me to brace them with
2X8's screwed between faces staggered and resting on the bottom
portion. Two rows. I am not impressed with TJI joists or the
Weiserhouser company.

HOW do I get the bounce or FLEX out of this floor?

Thanks

Duane Bozarth

2005-10-20, 4:21 pm

Xeroid wrote:
>
> I contacted the manufacturer of this joist before install. They told
> me it was the right residental joist I needed for my floor spanning
> about 17' 6". They told me I could space them either at 16 inches with
> bracing or on 12" centers without bracing. I installed them on 12"
> centers. 5/8 TG Plywood is screwed into place as the sub floor.
>
> PROBLEM ... the floor is way to bouncy. One man walking on the floor
> can feel it .... and if you are underneath you can see the joist move!
> Deflect downward! Maybe up to an inch ?
>
> I contact the manufacturer again .. now they tell me to brace them with
> 2X8's screwed between faces staggered and resting on the bottom
> portion. Two rows. I am not impressed with TJI joists or the
> Weiserhouser company.
>
> HOW do I get the bounce or FLEX out of this floor?

A typical joist calculator at
http://www.johnbridge.com/vbulletin/deflecto.pl

came back w/ the following--

"For joists that are Unknown wood, but in good condition, 12 inches
tall, 1.5 inches wide, 12 inches on center, and 18 feet long between
supports, the deflection calculated is 0.545 inches.

This translates to a deflection of L / 396.

Since the maximum deflection for tile is L / 360, ..."

Did you specify a maximum deflection? Did they provide an estimated
deflection spec in their quote? Sounds like they were sized for a
L/360 which is a typical number.

I suspect the only way to make a major difference will be to add a pier
in the basement which I suspect you were trying to avoid. Extensive
blocking will help some, but probably not nearly what you're expecting.

Unfortunately, looks like you should have had an engineer look at the
design for confirmation before proceding.

Bob Morrison

2005-10-20, 4:21 pm

In a previous post Xeroid wrote...
> I contacted the manufacturer of this joist before install. They told
> me it was the right residental joist I needed for my floor spanning
> about 17' 6". They told me I could space them either at 16 inches with
> bracing or on 12" centers without bracing. I installed them on 12"
> centers. 5/8 TG Plywood is screwed into place as the sub floor.
>
> PROBLEM ... the floor is way to bouncy. One man walking on the floor
> can feel it .... and if you are underneath you can see the joist move!
> Deflect downward! Maybe up to an inch ?
>
> I contact the manufacturer again .. now they tell me to brace them with
> 2X8's screwed between faces staggered and resting on the bottom
> portion. Two rows. I am not impressed with TJI joists or the
> Weiserhouser company.
>
> HOW do I get the bounce or FLEX out of this floor?
>

I just ran the calculation for the floor you describe and got an estimated
deflection value of about 0.30" for a full live load of 40 psf on the
entire joist length. The Defl/Span ratio for this load is L/710 which
exceeds the manufacturer's recommendation of L/480. I normally use a
minimum of L/600, so your floor should be quite stiff.

If there is no live load other than say a 250 pound person on the middle
of the joist, then the estimated deflection goes to about 3/16" for live
load at mid-span.

If you are truly observing an inch of deflection then something else is
going on. I suggest you have a local engineer review the situation or ask
the TJ field rep to investigate.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA

3D Peruna

2005-10-20, 4:21 pm

"Xeroid" <xeroid@kos.net> wrote in message
news:1129831926.513997.275330@g44g2000cwa.googlegroups.com...
>I contacted the manufacturer of this joist before install. They told
> me it was the right residental joist I needed for my floor spanning
> about 17' 6". They told me I could space them either at 16 inches with
> bracing or on 12" centers without bracing. I installed them on 12"
> centers. 5/8 TG Plywood is screwed into place as the sub floor.
>
> PROBLEM ... the floor is way to bouncy. One man walking on the floor
> can feel it .... and if you are underneath you can see the joist move!
> Deflect downward! Maybe up to an inch ?
>
> I contact the manufacturer again .. now they tell me to brace them with
> 2X8's screwed between faces staggered and resting on the bottom
> portion. Two rows. I am not impressed with TJI joists or the
> Weiserhouser company.
>
> HOW do I get the bounce or FLEX out of this floor?
>
> Thanks

Before you put the blame on TJI, you need to provide more information. If
the conversation was as brief as you report, then you ordered the wrong
stuff. You probably also didn't specify the deflection when you ordered
your joists. Sure, the joists are the right strength, but have more
deflection than you anticipated. Is that their fault or yours? Did you ask
them the question? If not, they provided joists that meet the minimum
deflection requirements, which sometimes are more than people like. You
could have specified a different series that would be more stiff.

BTW, they did suggest a way to stiffen the floor. The other way is to
reduce the space below with a beam (properly designed carrying the loads to
proper footings).

3D Peruna

2005-10-20, 4:21 pm

"3D Peruna" <w!h#a$r%o^l&d@w!e#i$r%d&n*e(s)s.com> wrote in message
news:uwR5f.7136$RG4.1574@fe05.lga...

Clarification: Minimum deflection requirements are more of a maximum
allowable deflection (yes...it's sort of a contradiction. The minimum
requirement is the maximum allowable deflection).

LinkBot