Reinforce attic trusses with structural steel tubing??

kennyja · Feb 11, 2013

I have attic space above my garage that I would like to convert to floor space for storage. Currently there are pre-engineered trusses in the attic.

I am wondering if I can install structural steel tubing next to the existing trusses to handle the extra weight. I plan to run tubing along the exiting ceiling, as well as along the roof line to augment the original truss. I am looking to span a 16" area for flooring

I am thinking 3.5" steel structural tubing should do the trick.

Thoughts?

Garage Flooring · Feb 11, 2013

As your question suggested, trusses are engineered. They take into account loading (including live loads) which would be items or people in your house overly simplified anything that can move, snow loads etc etc. The trusses then have bearing points which could be beams, posts, walls, etc.

So lets assume for a second that you carry the load successfully but you carry it to the wrong point... You really have not done yourself any favors. I would consult your local building supply source. They should have a relationship with a truss company. If you have original plans they can point you in the best direction.

BMBLBEE · Feb 23, 2013

What are you planning to store in your garage attic? I went through a similar excercise a few years ago wanting more space to store things in the garage. I had 4 sheet of 4x8x3/4" plywood cut into 2' x 8' pannels and screwed them down on top of the trusses in the attic. I did insulate between the plywood and drywall garage ceiling and even tied into the garage ceiling lights through a swith to have lighting up there.

This created a great storage platform. I do NOT store anything heavy in the attic just bulky light stuff that will fith through the 2' x3' access hole and have not had any problems. As mentioned earlier the trusses will be engineered to provide a safety margin for roof weight. My neighbor was so impressed we also did his garage attic.

Good luck with your project

rlitman · Feb 23, 2013

You mention 3.5" tubing, but is the span 16' or 16"?
This sounds like an awful idea. Steel is prone to lots of failure modes due to twisting where wood is not. I don't see that tubing adding much additional loading capacity, especially due to the added weight of the tubing. You really want to rethink this idea.

Xray Dave · Feb 23, 2013

I would check with truss companies before placing any kind of a load on pre-engineered trusses. They are engineered for the roof load, not a load on the bottom chord or ceiling rafter. Would hate to see a failure of bottom chord and have storage items land on top of your pride and joy.

KPSquared · Feb 23, 2013

I would get an engineer if you are planning to store anything heavy up top. Running a bunch of random steel may give you more strength or it may just overload your trusses and fail the whole system.

How's your engineering background?

The roof is not a thing to be messed with.

Most trusses are rated for a load on top, not on the bottom chord. That includes using them like an attic or hanging stuff from them.

Briansshop · Feb 23, 2013

I watched a buddy put a 8' 4x4 up in the bottom cord of his garage trusses and pull a smallblock AND turbo350 out of a Nova and the trusses never even made a peep. I was surprised for sure. Still wouldn't do it myself!

rodster_67 · Nov 21, 2013

KPSquared said:
I would get an engineer if you are planning to store anything heavy up top. Running a bunch of random steel may give you more strength or it may just overload your trusses and fail the whole system.

How's your engineering background?

The roof is not a thing to be messed with.

Most trusses are rated for a load on top, not on the bottom chord. That includes using them like an attic or hanging stuff from them.

KPSquared said:
or hanging stuff from them.

Old topic I know, but if the bottom chord is not designed for a load (other than maybe 5psf for a drywall ceiling, how are you suppose to suspend a garage door track, which will have a point load of more than 5psf when the door (16') is open?

I ask this question because I have to replace a non insulated 16' garage door that got twisted up by Hurricane Sandy (how it didn't cave in is beyond me) and after this experience I'm considering a insulated, heavier door.

The truss span is 24' and the door is 16' (parallel to the truss), so the weight of the door is being suspended 4' from the wall. Seat of the pants engineering :lol:

tells me it should be fine but....seeing 0-5psf bottom load in writing :scared:

me.

Garage has stood 15 yrs and survived Sandy but I don't want to overlook something at this point and have a problem.

Life was so much easier when I was young and didn't think about these things. :lol:

neel2008 · Nov 21, 2013

The trusses in my garage are store bought trusses. 24 foot span, 2x4 bottom string that is two seperate pieces with nail tabs holding them together.....scary I thought.....I wanted to be able to put some large light weight items up there as well as osb the underside and insulate without worring about those wimpy trusses. I sistered each bottom cord with a single 2x6x24. I beveled the first 5 inches of each end of the 2x6 and was able to lay it on the top plate one side at a time and "tilt" it up next to the trusses. I then used hurricane ties to fasten them together at the ends and to the top plates of the walls. I then screwed the 2x6's to the 2x4 trusses.... since the new board was taller than the original bottom string of the truss, I was able to "reinforce" the joints where the W of the truss connects to the bottom string as well as the center where the two halves of the original bottom string of the truss met. I am not an engineer at all and we can all argue about how I "messed up my engineered trusses" till the cows come home but the amount this firmed up each truss and completely eliminated the vertical deflection of the bottom string of the truss is undeniable.

LegacyIndustrial · Nov 22, 2013

This is the wrong venue for this but I wanted to give my two cents on the door.
Ask the manufacturer for a hurricane rated door. The entire east coast will likely be changing to this anyway due to Hurricane Sandy.

The state of Florida is a hurricane rated zone. Miami-dade being the highest rating.
I found this out when our dock door needed to be replaced.

Sent from my iPad using Tapatalk HD

rodster_67 · Nov 22, 2013

neel2008 said:
.......I am not an engineer at all and we can all argue about how I "messed up my engineered trusses" till the cows come home but the amount this firmed up each truss and completely eliminated the vertical deflection of the bottom string of the truss is undeniable.

What you describe is basically what I've been thinking about doing. Thanks for the details of what you did.

I agree with your thinking on how you "messed up my engineered trusses". I don't see how it can hurt and technically if you put the new 2x6 or any other additional support next to the bottom chord but don't attach it, it has to help the strength of the floor/ceiling and can't mess up the truss. But I'm not an engineer either and subscribe to Albert Einstein quote “In theory, theory and practice are the same. In practice, they are not.”

I'm tempted to try a little experiment. With my nailer, scab together about 3 2x4x12's for example, making up a 24' beam (alternating the joints of course), support it on the ends and jump :bounce:

up and down on the middle to see how much deflection there is. Some real world engineering. :headscrat

LegacyIndustrial said:
This is the wrong venue for this but I wanted to give my two cents on the door.
Ask the manufacturer for a hurricane rated door. The entire east coast will likely be changing to this anyway due to Hurricane Sandy.

The state of Florida is a hurricane rated zone. Miami-dade being the highest rating.
I found this out when our dock door needed to be replaced.

Sent from my iPad using Tapatalk HD

Glad to have your two cents. While getting door prices I actually asked about hurricane rated doors.

Not sure that is really needed but you never know. When I built my garage I used hurricane ties for the trusses and thought that was overkill. Glad I did when Sandy stopped by!

Thanks guys...

pauls_workshop · Nov 23, 2013

Hi, um, well, I am an engineer actually, but a mechanical. The kind of proposal to use steel in the original post is not entirely terrible but the details have to all be carefully worked out for your entire structure, as to how to connect that and transfer those loads, what sizes you would need, etc. Steel I type beams are a much better starting idea than tubing. A civil engineer could do such a thing but it would not be worth their time in general to do so or yours for the cost. Anything can generally be done somehow but is it worth all the trouble?

I found another thread at GJ where a structural engineer (subset of civil) was consulted for some changes to another fellow's building. They claimed about $400 for the advice. Something like this is probably what you should do to come up with the best way to handle your situation. Do not under any circumstance cut into any of those existing trusses or beams you have. - Paul

rodster_67 · Dec 30, 2013

Xray Dave said:
I would check with truss companies before placing any kind of a load on pre-engineered trusses. They are engineered for the roof load, not a load on the bottom chord or ceiling rafter. Would hate to see a failure of bottom chord and have storage items land on top of your pride and joy.

Since I'm thinking about hanging a much heavier insulated garage door from the bottom chord of the truss, I did just that. (Contacted 84 Lumber, the company I bought my trusses from)

I was told, no problem. Said if you calculate the actual load on one hanger, 100lbs for example, the point load is negligible and nothing to worry about. Even less to be concerned about if the hanger is attached to 2 trusses and the load is distributed over both.

Common sense and the lack of ever hearing about a bottom chord failure due to storage/loading, told me it was not a big concern but thought it best to contact the truss manufacturer just to be sure.

Reinforce attic trusses with structural steel tubing??

kennyja

New member

Garage Flooring

ALLIANCE MEMBER

BMBLBEE

Member

rlitman

Well-known member

Xray Dave

Member

KPSquared

Well-known member

Briansshop

Member

rodster_67

Well-known member

neel2008

Well-known member

LegacyIndustrial

ALLIANCE MEMBER

rodster_67

Well-known member

pauls_workshop

Well-known member

rodster_67

Well-known member