Web floor trusses--what is greatest span?

Old 03-27-06, 05:09 AM
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Web floor trusses--what is greatest span?

Hello all,

I am thinking of using these in a home design and am curious about how far these will span without the use of a beam. I can't find any *hard* data but I came up with around 30'. I currently have a rectangular-ish home plan roughly 35' wide that incorporates I-Joists with a single steel beam running down the center. I was thinking of changing the home design to more square, which would be around 50' x 40' (roughly). Seems all homes with similar dimensions(using I-Joists) will have two beams in the basement for support as 40'-50' gets to be a little long. Hence the question..

Doug, if you are reading this I'm still debating as to wether I'm going to build the current home, have you design me one, or just buy one. So many options I just want to make the right decision for me(and the money!).

Thanks for the help,
Old 03-27-06, 03:12 PM
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Web floor trusses--what is greatest span?

When it comes to maximum truss spans, there are a number of different criteria.

1. From a strength standpoint, a truss will span much farther than you really want it to.

2. There is a criteria for deflection: length/some fictitious number.

3. There is the comfort/feel factor that gives a "feel" for the quality of the home.

Since you are considering wood, which is springy and does deflect, columns and beams cutting span lengths do wonders to make the home feel more substantial than it really is.

A well designed layout using columns and beams can give you the cheapest solution and a "good feel". You could also go with 8" prestressed concrete plank and get a much larger open area without the spring, bounce and deflection. - This is the international approach where wood is looked on a substandard construction.

It all depends on your budget and standards.

Old 03-30-06, 08:56 AM
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the reason for (2) column lines is that it is cheaper to add one girder line than it is to pay the additional cost in material for all the joists. With a center beam design I would simply use 12" TJI projoists @ 16" o.c. as they span 24' and low in cost.

With regards to choosing between assitions, new homes, or custom homes I always tell my clients this:

what is your house worth right now. what is it worth with the addition you are talking about adding. what was the cost to get there.

Can you buy what you are looking for for the cost that you would have into your home. If you buy you are paying someone else for the equity you already have in your home.

If you build from scratch you will have instant equity, is it the same as what you would have in your current home? Here in California it iseven more critical. We are reassessed for property taxes only at the purchase or on a remodel. If we do a remodel we are only assessed on the remodel portion. So for us to replace just what we own our property taxes often double or tripple. Additions are a great way to go in this climate. Others who are reassesed often have other considerations.

Good luck,

brian garrison

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