Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Shop & Safety

SFT Search:   
Reply
 
Thread Tools Display Modes
  #1  
Old 08-29-2019, 10:07 PM
Scratch Scratch is offline
Senior Member
 
Join Date: Feb 2007
Location: Hudson WI
Posts: 526
Default Floor truss design questions

I have these floor trusses that a builder gave me after the deal on a house fell through. They were brand new when I got them about 10 years ago, but have been stored inside since then. I want to know what they'll span and am hoping someone here might be able to help me figure that out.

They're made with 2x4 construction, with the usual galvanized connceting plates at all the joints. They are both about 27' 6" long and 20" high. I have a bunch of the top ones and 2 of the bottom ones.
I want to use these in my pole barn to make a ceiling and loft storage space above it.

I need them to be able to span 17'. Two feet on center.

Any truss designers out there?
Attached Thumbnails
Click image for larger version

Name:	Screenshot (22).png
Views:	75
Size:	33.3 KB
ID:	151997  
Reply With Quote
  #2  
Old 08-29-2019, 10:27 PM
milomilo's Avatar
milomilo milomilo is offline
Auction Addict
 
Join Date: May 2010
Location: Wheatland, Wyoming
Posts: 15,431
Default

What is your plan for roof trusses? Will the floor trusses be below the roof trusses?
__________________
Chris

Liberty has never come from Government. Liberty has always come from the subjects of it. The history of liberty is a history of limitations of governmental power, not the increase of it.
Woodrow Wilson
Reply With Quote
  #3  
Old 08-30-2019, 07:00 AM
Scratch Scratch is offline
Senior Member
 
Join Date: Feb 2007
Location: Hudson WI
Posts: 526
Default

Quote:
Originally Posted by milomilo View Post
What is your plan for roof trusses? Will the floor trusses be below the roof trusses?
Yes, this is going in an already built pole barn with 16' sidewalls. I've recently decided to section off a portion of it and want to use these floor trusses for the ceiling so I can have storage up above it.
Reply With Quote
  #4  
Old 08-30-2019, 08:46 AM
milomilo's Avatar
milomilo milomilo is offline
Auction Addict
 
Join Date: May 2010
Location: Wheatland, Wyoming
Posts: 15,431
Default

Now I understand. Are you looking for load data? How are you attaching to the existing structure?
__________________
Chris

Liberty has never come from Government. Liberty has always come from the subjects of it. The history of liberty is a history of limitations of governmental power, not the increase of it.
Woodrow Wilson
Reply With Quote
  #5  
Old 08-30-2019, 09:18 AM
Scratch Scratch is offline
Senior Member
 
Join Date: Feb 2007
Location: Hudson WI
Posts: 526
Default

Quote:
Originally Posted by milomilo View Post
Now I understand. Are you looking for load data? How are you attaching to the existing structure?
The building is 40'X63'. I'm building a small, 4 walled, room in the corner about 24' x 27'. The room will be attached to the posts on two sides in one corner, with free standing walls on the other two sides.

That room will be divided in half with a load bearing wall at about 16.5'. I just need to know if this truss design will safely span a 17' distance if used 24" on center.
I'm pretty sure they will as I also have another room that is using 12" TGI's that are rated to span that distance easily. I thought that floor trusses have a greater strength than TGI's, but wasn't sure and was hoping there might be someone here that knows this info.

I had a good friend that designed roof and floor trusses for a large company. He told me to send me a sketch of the trusses and he could easily tell me right away if they would span that distance. Unfortunately... that friend died a few months ago and I never got to send him a sketch.

Here's a rough drawing of what I'm trying to do. Walls in blue, floor trusses in grey.
Attached Thumbnails
Click image for larger version

Name:	Screenshot (23).png
Views:	39
Size:	10.4 KB
ID:	152001  
Reply With Quote
  #6  
Old 08-30-2019, 09:26 AM
Scratch Scratch is offline
Senior Member
 
Join Date: Feb 2007
Location: Hudson WI
Posts: 526
Default

I just Googled: "Floor truss span" and found this chart:
According to this, their 20" tall floor trusses can span 23'-10" if placed 24" OC. Which is more than I need since I'll be having a load bearing wall at about 17'.

This is the number I'm looking for but I have no idea who made these trusses.
Attached Thumbnails
Click image for larger version

Name:	Screenshot (24).jpg
Views:	39
Size:	100.2 KB
ID:	152002  
Reply With Quote
  #7  
Old 08-30-2019, 11:25 AM
BukitCase BukitCase is offline
Elite Member
 
Join Date: Feb 2013
Location: Lost in Oregon
Posts: 1,091
Default

Marked up your drawing; this is the MINIMUM I would do to use those trusses as you're intending.

Notice that the originals have a double 2x at each end? These are the ONLY intended support points (like between two load bearing walls) - if you try and use them between two points that are 17' apart, the midpoint support will collapse that section (the lower chord first) because the supported weight will be pushing down where there is no direct transfer of the weight to the load bearing wall.

Ideally, those "triangles" in that section should be changed so their end points coincide EXACTLY with the 17' support point, and another vertical added at the load bearing wall.

My drawing should work OK, but likely wouldn't be as strong as "re-designing" that one 5' section. The 6" offset is the reason I added the extra sister of that bottom chord - not ideal, but less difficulty to do than re-cutting ALL the interior chords to meet your 17' support point.

It would be better if you could move your support wall to EXACTLY 17 1/2 feet AND add that upside-down "T"... Steve
Attached Thumbnails
Click image for larger version

Name:	Scratch-1.png
Views:	52
Size:	27.2 KB
ID:	152003  
Reply With Quote
  #8  
Old 08-30-2019, 01:12 PM
Scratch Scratch is offline
Senior Member
 
Join Date: Feb 2007
Location: Hudson WI
Posts: 526
Default

Quote:
Originally Posted by BukitCase View Post
Marked up your drawing; this is the MINIMUM I would do to use those trusses as you're intending.

Notice that the originals have a double 2x at each end? These are the ONLY intended support points (like between two load bearing walls) - if you try and use them between two points that are 17' apart, the midpoint support will collapse that section (the lower chord first) because the supported weight will be pushing down where there is no direct transfer of the weight to the load bearing wall.

Ideally, those "triangles" in that section should be changed so their end points coincide EXACTLY with the 17' support point, and another vertical added at the load bearing wall.

My drawing should work OK, but likely wouldn't be as strong as "re-designing" that one 5' section. The 6" offset is the reason I added the extra sister of that bottom chord - not ideal, but less difficulty to do than re-cutting ALL the interior chords to meet your 17' support point.

It would be better if you could move your support wall to EXACTLY 17 1/2 feet AND add that upside-down "T"... Steve
Ok, I see what you mean by needing a vertical in there at the support point. So if my trusses are 27.5' long, and I hypothetically make my wall at like 26', could I safely change the truss by cutting off about a foot and a half and add some pieces like this:
Attached Thumbnails
Click image for larger version

Name:	Screenshot (25).png
Views:	41
Size:	46.4 KB
ID:	152005  
Reply With Quote
  #9  
Old 08-30-2019, 01:17 PM
Scratch Scratch is offline
Senior Member
 
Join Date: Feb 2007
Location: Hudson WI
Posts: 526
Default

Also, hypothetically.... if I wanted to make one room, not split in half and wanted the support wall to be at like 15', could I just modify the truss to something like this and be safe:
Attached Thumbnails
Click image for larger version

Name:	Screenshot (27).png
Views:	39
Size:	41.9 KB
ID:	152006  
Reply With Quote
  #10  
Old 08-30-2019, 01:20 PM
BukitCase BukitCase is offline
Elite Member
 
Join Date: Feb 2013
Location: Lost in Oregon
Posts: 1,091
Default

Yup, that'd give you the straight vertical transfer at the supported ends of the truss - everything in between is still just a bunch of triangles stuck together, which is what makes the EFFECTIVE depth of that "board" (truss) 20", but at a lot less WEIGHT than a 4x20 solid board would be... Steve
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 07:12 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.