how to specify wood I joists on drawings 1

[HouseBoy]

I’m wondering how everybody does this.
There are so many different I joist products that might end up on the job usually depending on which lumber yard the builder goes to.
Some suppliers provide a layout drawings (much like roof trusses) but it is not provided to the architect or the consulting engineer for review.
Also, different flanges can be selected (either by the engineer or the designer/supplier.
How do folks typically indicate wood I joists on drawings? Do you indicate depth and performance spec?
Do you pick a maker and indicate their product and say “or equivalent”.
How often do you get to see shop drawings? (what about BEFORE the joists are purchased (and installed)

Is there a “generic” spec for these products?

 

[MiketheEngineer]

I usully spec a size and mfg "or equal" with the supplier responsible for the final design. Most won't sell them until their engineers review.

IF I get a chance - I will review their selection. I don't seal that part of the work even if my prelim design picked the right size.

ALWAYS use the 1/480 table for floor design and be conservative. Say if you need 15' - pick the one that goes 16-6 instead of 15-2. A few extra bucks will often solve a lot of vibration problems

 

[COEngineeer]

I put for example

11 7/8 BCI 6000 @ 16" O.C.

Then on your general notes say that the joists are 11 7/8 BCI 6000 or equivalent.

Never, but never question engineer's judgement

 

[RARWOOD]

I would specify the product you prefer to use. For example LPI's from LP or TJI's from Trus-joist. Write your specifications so detailed shop drawings are available. Another reason for specifying the company you prefer.

 

[whyun]

Showing the manufacturer and the specific joist type on the drawings is preferred. Note should require that the layout drawings be submitted to the architect and engineer for review. Also, any alternates shall be approved by architect/engineer.

 

[FSS]

I put minimum acceptable values for EI, moment capacity, and shear for the joist I want (get them from catalog of the joist you have used in your analysis). The capacities between brands can be significant for some size groups, even when the dimensions appear the same.

 

[HouseBoy]

"The capacities between brands can be significant for some size groups, even when the dimensions appear the same."

My understanding from talking to some product reps is that the main differences have to do with a given companies willingness to accept higher values. I think it's a sale thing. The products are all made the same (i.e. most products come from only a few manufacturers and each seller puts their own name on it. Everyone wants to be the one with the greatest capacity for their joist so they each inch up slightly over time – just to say they have the greater capacity than someone else.
It seems like the values are changing slightly about every 6 months.
Anyone know more about this? (I trust that I am not hijacking my on thread)

 

[ctcray]

I haven't come across a drastic difference between brands of equivalent sized I-joists as far as allowable spans/capacities go. Besides, when the drawings call out '14" LPI/TJI/GFCI/etc joists @ 16"oc', our supplier does their own layout/takeoff to ensure the correct product for the actual spans is provided.

However, for LVL, the Fb and E values are all over the place even in the same brand, so it's very important to spec the required design values for these.

Perhaps the manufacturers should agree on a color scheme for the different grades of LVL, ie, 2600-1.9E is blue, 2900-2.0E is orange, etc.

Then throw in LSL to the mix to confuse people even more. =)

 

[Whodapookie]

From the supply yard side (the people that actually cut and deliver the I-joists), it is easier for the designer to specify the depth, loading, max on center spacing, and performance requirements and let them determine everything else. Sure, this seams vague, but there are many manufactures (which is getting thinner due to the housing market) and each have many different grades of product (iLevel has 5 series at multiple depths). This allows the suppliers to optimize the design per the products they carry and provide the owner with their most economical solution.

Specifying the minimum Fb, Fv, & E is ok, but you have to realize there are 2 different "E" values (E true and E apparent) which not all manufactures report the same one. Whatever you do, always specify at least L/480 for live load deflection.

From the above posts, you can tell there are many differing opinons on this subject. Talk to your contractors, suppliers, etc. in your area to see what works best for the whole team.