Thread: Engineered floor truss

At an inspection yesterday of a town home built in the early 80’s I found these truss floor joists.

The upper 2 X 4 members of these truss floor joists are set into masonry pockets in the concrete block foundation walls but the lower 2 X 4 members are not. They just end at the foundation wall on both the left and rigth sides and there is not a main center support beam for the span, which is pobably not necessary because of the engineered trusses (if they were properly installed) .

The floor was found to have a moderate amount of deflection in it when walked across with heavy feet.

I would feel that these bottom members of these truss floor joists would need to be supported in the foundation wall more so than the upper member.

I told my client that I would look into this issue but that that a structural wall would probably need to be built under then ends of these truss floor joists along side the foundation wall for proper support.

Any opinions or information regarding these truss floor joists and how they should be installed would be greatly appreciated. Also, I have some more pictures of them and can comment further if needed.

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SL: Since these are engineered members a structural engineer will be required to specify the repair of this apparently abominable installation. Perhaps the addition of a metal angle on each end to support the trusses would suffice, if properly sized and fastened to the concrete block foundation walls.

It does not appear that the upper portions of the trusses have sufficient space around them in the pockets in which they rest. That may be difficult to repair.

The pictures show a top chord bearing truss. It is a correct installation.

http://www.turkstratrusses.ca/pdf/Builders_guide.pdf

Turkstra Trusses - Truss Downloads

RA is correct. The end of the floating portion will typically be painted or have some other factory marking to show it hasn't been cut on site.

Originally Posted by Ken Rowe

RA is correct. The end of the floating portion will typically be painted or have some other factory marking to show it hasn't been cut on site.

KR: While RW may have posted a possible answer, I see no indication on the ends of the bottom chords that would lead me to believe these were not field modified. Additionally, and as is almost always the case, SL (as well as both you and RW) did not have the benefit of viewing the truss schedule for this house. So then, at best you are hypothesizing. At worst you are giving bad advice.

That is why I said "Since these are engineered members a structural engineer will be required to specify the repair of this apparently abominable installation."

AD

Sorta like your comment "abominable". You did not have the luxury either to review the documents for these trusses and make the comment you did. Further you provide no documented proof. Please enlighten us further.

Please enlighten us further.

RW: With you, the question is: where to begin . . .

I am pleased you see the humour in your faults!

Originally Posted by A.D. Miller

KR: While RW may have posted a possible answer, I see no indication on the ends of the bottom chords that would lead me to believe these were not field modified.

AD, there is no picture of the ends of the bottom cords so of course we can't see them. However, if the original poster looked at them he may have seen the markings.

Another way to tell if they're "field altered" is the quality of the cut. Nice, straight cuts with little tear out are most likely factory cuts.

Just curious -- Assuming that it is a correct installation of a top chord truss, do you have any recommendations for the “moderate amount of deflection in it when it is walked across with heavy feet?”

Light feet

A strongback at midspan might help a moderate amount of deflection.

I believe web stiffeners could be added.

Wow. Thank you all for the input. I will be going back to the property tomorrow and will check the ends of the trusses for factory markings and make sure they were not altered. I’ll look into the web stiffeners suggestion to help with the deflection issue. I figured that this post would get some feed back. Thanks again.

While I don't see a lot of top loading floor trusses, I have seen a few that looked just like this.
You might be able to find a tag from the truss manf. and contact them and see if they were installed according to their specs. Though, since it was built in the 80's, this may be a dead end.

I would steer clear of giving any kind of advice about how to stiffen the floor. Even if you are a structural engineer, I would not have that as part of my home inspection documents/service.

When I inspect a house with trusses, I always looked for the tags that say "Bearing point here" and "Strongbacks required here". Many times those parts are missing. Of course, many times the tags are missing too.

Given the age and lack of documents, you don't know whether these trusses are spanned correctly or whether the on-centre spacing is correct. In which case you may be advised to refer to an engineer familiar with this system. Contacting a local truss manufacture for advice or referral to an engineer would be a good bet.

FWIW, Your pictures show a doubled top cord. I've never seen a doubled top cord that is not intended to be top cord bearing.

Ken -- have you seen many top chorded trusses like these around here?

Originally Posted by A.D. Miller

That is why I said "Since these are engineered members a structural engineer will be required to specify the repair of this apparently abominable installation."

If no crack or damage is found on the floor trusses, I cannot understand why a structural engineer is required after the 30-years long actual live loading test was performed.

Wood Truss Products

See strongback diagram. This is an alternative bracing method, fyi.

Originally Posted by Jon Errickson

Ken -- have you seen many top chorded trusses like these around here?

I've seen probably less than 300 top chord bearing trusses and less than 50 that have been altered. Very common to see in the 70's and 80's when the "sunken" living rooms were all the rage. Every one that has had the doubled top cord (that I've seen) has been top bearing.