Truss modification anyone have any experience?

[Strouty]

I have a standard roof truss with the "w" web that has 2x6 top and bottom chord with 2x4 webs. The span is a little weird, I had 2x4 walls, then added another 2x4 wall inside that. So I am not sure if it changes my bearing area or not. The span was 30' before we added the interior 2x4 wall. The trusses are 24" OC and I would like to change the ceiling profile from flat to a box style. This would be used to gain height for a second level. I am thinking of boxing both sides with plywood, at this point I have talked with two engineers and both do not like anything to do with modifying trusses, one has given advice, but will not do a design. I am going to call a local truss manufacturer and see what they say, I figure it will be do to blah blah blah we can't help you. Has anyone had any experience doing this or something like it? I don't want to cut anything until I have a safe design and plan of action. I could not get actual pictures, my camera focused on all the freaking dust from the insulation instead of the trusses.

 

[p_mori7]

Re: Truss modification anyone have nay experience?

Maybe ask a truss company to design a truss for a "possible" future building...that would have exact same dimensions & requirements as your current plan ?

That way you will get to see how they would build the trusses and what the spacing specs would be...without venturing onto the slippery slope of getting advice on modifying trusses built by somebody else.

It should give you a good starting point.

 

[Homerr]

Re: Truss modification anyone have nay experience?

There is a simple reason you are getting this advice. Modifying trusses is a BAD idea. Rip it off an start over with new stick built roof or trusses configured in the way you want.

 

[ADSR]

Re: Truss modification anyone have nay experience?

As a home builder, we do this all the time. Call the truss guys and ask them for a repair detail.

 

[soapii]

I will post some more information tomorrow about this, I did exactly what you are looking to do. I'll post pics too.

--Joe

 

[Strouty]

As a home builder, we do this all the time. Call the truss guys and ask them for a repair detail.

I will post some more information tomorrow about this, I did exactly what you are looking to do. I'll post pics too.

--Joe

Thanks guys, I will be talking with the truss companies in the area today. I look forward to seeing those pictures too!

 

[soapii]

Attached are a bunch of pictures I took along the way. I had to modify my trusses because I ended up wanting a slightly taller than 12'-0" lift and my ceiling was at 11'-9". I ended up just doing an 8" box to provide ample room for anything.

I originally contacted the truss company who made my original trusses and got to talking with them. They sent me back revised CAD sketches of what modifications where needed. I'm a civil engineer so at the same time, I had a couple of the structural guys here at work model the trusses how I planned to modify them and they came up with a similar solution.........so I went to town.

I went overkill and used larger gusset plates and I also used adhesive on all connections. Further I doubled up all bottom chords and added another hurricane brace. I was very happy the way everything came out. Let me know if you have any questions.

Pics to come........and sorry but most are standing on the ground looking up towards the trusses.

--Joe

 

[soapii]

More...

--Joe

 

[soapii]

Some more...

--Joe

 

[soapii]

Last couple. Sorry but I don't have any pics of it all painted, wired etc.

--Joe

 

[JakeKohl]

It's just math and material science. As long as you are doing it by utilizing the right knowledge, modifying trusses is fine. Soapii has a fine example of such a modification.

 

[Strouty]

Thanks for the pics, I think I may not be able to do what I want. I need to remove 2'6" of the bottom chord for a span of about 20' on 6 trusses. I may be able to have new scissor trusses designed and then install them in pieces before removing the parts of the existing trusses.

 

[LX-Markham]

It's just math and material science.

That's called "engineering"

Modifying trusses is not "a bad idea". Anything is possible, it just takes some planning and some money. The engineers you have talked to either are not familiar with modifying trusses, or simply don't want the job.

Strouty, anything is possible. I took our trusses and completely removed them to create a vaulted ceiling.

 

[Strouty]

Local truss companies said sorry unless they are our engineered trusses we can't/won't help.

 

[LX-Markham]

^^^yeah, they don't want to mess with another man's rhubarb ...I mean truss design.

I work for a structural consulting firm, and we probably wouldn't take the job either LOL, sorry.

 

[gungatim]

LGR!

 

[gungatim]

LGR!

 

[Strouty]

You guys are being way more positive than I expected. I appreciate all the pictures as well. I have talked with a few engineering firms and most don't want to touch it. The ones that will have come back with a $2000 plus price tag. I am a little worried that if they design it for me, that I may not be able to afford to build it to the designs they have been talking about. I am glad I am not in a rush to do this.

 

[LX-Markham]

That price probably includes surveying and measuring the existing trusses so they can do their design calcs.
How old is the building? If you can get your hands on the building permit drawings with the truss design drawings, it would save the engineer a ton of time and likely reduce the cost.

But $2k at an engineers rate of say $150/hr. is about 2 days of design work (including any site work).

 

[Strouty]

That price probably includes surveying and measuring the existing trusses so they can do their design calcs.
How old is the building? If you can get your hands on the building permit drawings with the truss design drawings, it would save the engineer a ton of time and likely reduce the cost.

But $2k at an engineers rate of say $150/hr. is about 2 days of design work (including any site work).

The building was built pre permit requirements in 1972 so it was just built. It appears to be consistent with standard designs. I am not opposed to paying what it is worth, I just don't know what it is worth. A few people have said they will come and look at it for free, others want big bucks just to look at it. I get $75 an hour for my business, but I don't charge to give a price unless it involves plane rides or some remote access.

 

[Strouty]

I finally found someone who is realistic. He told me $135 an hour and bring pictures and dimensions of project. He thinks between $300 and $500 to do the redesign of existing trusses or a complete modification. I will keep people updated as I am sure there are more than a few people who want todo things like this either for car lifts or second floors like me.

 

[mpire]

Its funny, a friend of mine asked me to help him redesign his trusses to make room for a small laundry room. The difference is that he wants to put the laundry room inside the trusses, so we want to empty them out so to speak to make room.

I am not an architect, but I do have a degree in Architecture, so I figured I would get out the old textbooks and figure this out. I assumed we would just make new trusses and then screw them to the old trusses and then cut out the centers of the old ones. Can 2x4s support the load of a floor? I don't think so, wouldn't we need to go with 2x6s?

Can someone please come over and dig my 20 year old textbooks out from under the stairs?

 

[Strouty]

Its funny, a friend of mine asked me to help him redesign his trusses to make room for a small laundry room. The difference is that he wants to put the laundry room inside the trusses, so we want to empty them out so to speak to make room.

I am not an architect, but I do have a degree in Architecture, so I figured I would get out the old textbooks and figure this out. I assumed we would just make new trusses and then screw them to the old trusses and then cut out the centers of the old ones. Can 2x4s support the load of a floor? I don't think so, wouldn't we need to go with 2x6s?

Can someone please come over and dig my 20 year old textbooks out from under the stairs?

I would think that the minimum you would want would be 2x6 not 2x4 and probably even 2x8.