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twiles 07-02-2008 06:35 PM

Building Garage with Engineered Trusses
Hello all,
I am new to the site and looking for some help. I am building a 24 x 28 garage that has 9 foot walls and engineered trusses. The trusses have a room built into them that is 12 foot wide with7 foot walls that follow the pitch of the roof above the 7 foot mark. Here is my problem. I am trying to figure out the best way to frame in the stairway into the trusses. The stairs are being placed in the back of the garage on the back wall (24 foot). Option 1 - set all of the trusses 16" OC and cut the span boards after they are set and frame in the stairwell opening. Option 2- leave two trusses out, double up one truss (fasten two trusses together). The stairs are 48" wide which means there would be a 60" span between the last truss (one that is set on the rear wall) and the double truss located on the opposite side of the stairs. I would latter frame all the way around the truss every 16" OC with 2 x 8 boards 5 feet in length. The truss company says either method is acceptable however option 1 requires modification instructions from them (no big deal). The problem is my fatherinlaw says I am crazy for wanting to do option 2. This is why I am asking for your help. What is your advice? Which method is preferred or better? Thanks in advance.....

Termite 07-02-2008 10:13 PM

Welcome to the site.

So who managed to forget the minor detail of stairs??? :no:

I'd go with option number one, provided that your truss company will support you doing it. If they'll give you an engineered repair, that is the way to go. Just be sure you follow it to the letter. Engineered repairs for trusses are typically produced using MiTek or Alpine (or similar) software and engineering support, and they have tiny print and a lot of fine details. The details will include the nail size and spacing, sometimes glue, the exact materials to be used for the repair, etc. If they give you a fix, it is the way to go.

Don't modify the design or the layout to get the opening width. You'll have to frame from truss to truss to get your floor and roof sheathing to span. Doubled trusses will often telegraph through the roofing materials as well...You might eventually see a bump, depending on the roofing.

twiles 07-03-2008 05:15 PM


Thanks for your response!!! The truss manf. did not listen when we called them to place the order and told them there would be stairs on the back wall. Also, when you order trusses that have a room built into them and you are placing trusses 16"OC that ought to send a big red flag up that says "this guy is going to need stairs". Anyway, the truss manf. is using MiTek software and I confirmed today that they will provide me with a repair procedure for modifying the trusses to frame in an area for the stairs. I was mostly confused about which option to use. I appreciate your advice! Thanks....

Termite 07-03-2008 10:30 PM

Sounds good to me. FOLLOW THE FIX TO THE LETTER. Small details make big differences with the reactions in trusses under load.

medeek 01-12-2013 07:40 PM

Stairwell with Engineered Attic Trusses.
I've attached an image that shows a stairwell framed parallel to the trusses at one of the gable ends. The gable truss is designed to also be a load bearing truss over openings below so that is the reason for its complexity. If anyone has any suggestions on this I would be interested to hear them. The span of the trusses is 28 feet, 24" o/c.

My website does have a good 3D model of this sort of assembly (eDrawing) if it helps any.

AndyGump 01-12-2013 08:15 PM

So let me guess, you are a truss designer and you are trolling building related talk sites to hawk your wares?


Missouri Bound 01-12-2013 08:27 PM

...and your website is swiss cheese.....:whistling2:

medeek 01-12-2013 10:19 PM


Originally Posted by AndyGump (Post 1092069)
So let me guess, you are a truss designer and you are trolling building related talk sites to hawk your wares?


Actually I design garages, sheds and other small residential structures on the side. I usually get BMC West to design my trusses once I have a floor plan established, I particularily like the Mitek software they use. It's too bad Mitek won't sell their softare to anyone except the truss plants, it would sure be helpful sometimes.

The picture I posted shows how I dealt with the stairs coming up through the trusses. What I am curious to know is if there are better ways to do this or alternatives to what I have done. It seems to me that the best way to bring stairs through any floor or roof is generally run them parallel to the spanning members.

Its actually quite a compliment to be mistaken for a truss designer, I guess my drawings are pretty good. I just put up my website a couple of months ago and I am offering all of my plans for free (via PDF), I like the whole open source model and I think putting it all out there is the way of the future.

Maintenance 6 01-13-2013 10:18 AM

I sorta doubt that the OP is still waiting since July of 2008 for a solution.

medeek 01-15-2013 03:13 AM


Originally Posted by Maintenance 6 (Post 1092338)
I sorta doubt that the OP is still waiting since July of 2008 for a solution.

Probably true but someone else will have the same question, I did.

mr leak 01-21-2013 10:55 PM

garage trusses
The picture is commonly known as "truss laddering" also used when the truss company forgets a truss. Usually not a big deal and have the truss company stamp the ok at no charge It is no more than running the calcs thru their computer program NO CHARGE

medeek 06-15-2013 03:10 PM

Truss Designer
I am a truss designer now... :)

I've recently started working on a truss design software that will hopefully one day compete with the big boys out there. I'm still working on the plate and member sizing portions but so far I've pretty much got the geometry worked out for a number of common trusses. Here is a recent output from the CAD Generator (Fink Truss only for now):

Give it a whirl and tell me what you think. Remember it is still very much a work in progress:

medeek 06-15-2013 03:14 PM

Here is a sample output for the loads on a double fink truss:

medeek 06-15-2013 03:15 PM

I've kind of hit a road block on the moment calculations. The current spec TPI 1-2007 calls for using the matrix method in determining the moments. However, I need to be able to run this app without doing a full blown analysis using RISA or some other FEA type product. For now I've gone with the simplified method which is the method used in the TPI 1-1995 standard, at least I can produce a solution. Typical result below:

If anyone has any ideas on how to do a simple matrix method analysis of a common fink truss please send me in the right direction. My biggest unknown with this would be how to deal with the fixity of joints at panel points and heels. I've just ordered a copy of Hibbeler's Structural Analysis to further research how best to deal with frames, trusses etc...

One thing I found really helpful was the samples provided in the previous editions of the TPI 1, its really quite disappointing to see no such example calculations in the current standard.

AndyGump 06-15-2013 03:27 PM

I am going to keep this page as an example to everyone who asks me why engineering seems so expensive.
It is NOT expensive when you consider that it takes really smart guys (or gals) like this to work up a solution for their very specific situation.

I can't do it and am happy there are people who can.

Thank you MeDeek.


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