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28' span open web floor truss 24". Solid or not?

Squirtel8056's picture

I'm building a house here in April. I have had 2 contractors tell me they would be solid and one would not recommend them. Said they would be to bouncy.  Is it a solid floor? Or good idea



thank you for the advice

. (post #214467, reply #1 of 2)

I designed trusses for close to 30 years.  Even built my own house with clear span floor trusses, which just happened to be a 28' span and 24" deep.

Before I get into details - You might be interested in a thread I wrote many years back about floor vibration:

Your floor trusses are well within the limitations of what I feel are acceptable.  And I'm pretty danged conservative on floor design.

One caution I would give you - Make sure the builder installs strongbacks.   If you don't know what they are, here's an article that describes them:

That article has a good illustration showing the strongbacks.  But you can ignore the BS about the trusses twisting so much the plates back out.  I have never heard of that actually happening.

The purpose of a strongback is to reduce vibration.  It spreads the impact load of someone walking across more than one truss. They're not structural, and are highly recommended but not required.   I recommend putting them towards the bottom of the truss rather than the top.

The strongbacks are typically 2x6 with the wide face vertical. They should be nailed to a vertical member in the floor trusses, roughly at 10' spacing across the span of a truss. Where there are splices they should be lapped at least one truss spacing

In a perfect world the strongbacks are supposed to be fastened to something at the end of their run. In reality, it doesn't really bother me much if they aren't.

In an existing house, it's incredibly difficult to get more strongbacks in the truss space. I've tried.  Make sure they get put in as the floor trusses are set.

These trusses should give you one hell of a nice basement, and plenty of room to run mechanicals in the trusses.  

Consider this - Have you ever known anyone who said "I sure wish I had more posts in my basement"?    Of course not.  But you can find lots of people who want to find a way to get rid of a post that's in their way.

Hope your house turns out great.

I built a lot of houses with (post #214467, reply #2 of 2)

I built a lot of houses with 24' open web floor trusses. I'd put them in my own home tomorrow.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.