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Old 08-14-2009, 04:56 AM   #1
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Floor Truss Shortening


I am in the middle of converting a duplex to a single family home. I just got the letter back from the engineer saying that we need to install 3 LVL beams inside the ceiling (I want a flat ceiling, so we are hiding the beams).

The LVL beams will run perpendicular to the floor trusses. For beam #1 we need to support the floor trusses, cut seven of the floor trusses, install the beam, then anchor the seven trusses to the beam.

The floor trusses are 20 inches high and span 20 feet. Each is made of 2x4s with lots of webbing.

So I need to cut 7 floor trusses, really shorten them by 4 feet. Is there an accepted technique for doing this? The engineer didn’t say anything in his letter.

I’m guessing I need to glue and nail some sort of plywood material and around each truss at the cut point.


Last edited by bmcgin; 08-14-2009 at 04:59 AM.
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Old 08-14-2009, 07:12 AM   #2
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Floor Truss Shortening


Floor trusses are engineered products. Did the structural engineer know you had floor trusses or did you just find this out? Your engineer will have to sign off on the method used to put them back together and on what type of hanger and fastening methods to use. As far as cutting them once they are braced remove the gusset plates (if there in the cut line) and cut with a reciprocating saw. You could start the cut with a circular saw but be cautious of nails and kick back if you do.

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Old 08-14-2009, 07:35 AM   #3
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Floor Truss Shortening


We removed the drywall around the bearing walls and ceiling before the engineer came to visually inspect, so he knows there are trusses and not 2x12s. He did specify to use the Simpson Joist hangers to attach the trusses to the beam.

He did not instruct how sure up the floor truss after it’s cut. The beam will essentially go right through 7 floor trusses so it can reach the outside wall.

Before cutting the truss, should I box in the truss with plywood and glue? How can I make the truss strong again so it can attach to the beam?
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Old 08-14-2009, 08:25 AM   #4
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Floor Truss Shortening


By box in I'm going to assume you mean use plywood as a gusset plate. Yes you should, but you should also get your engineer to sign off on it. If you don't you're probably going to have problems when you get it inspected. It's not necessarily a matter of will this work or will that work in these situations. It's a matter of who is willing to except liability if it doesn't work. Make sure you get him to spec the thickness, type of plywood, and fasteners required. He should have done this for you if he knew there where trusses that needed to be altered.
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Old 08-14-2009, 08:41 AM   #5
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Floor Truss Shortening


The engineer did specify a lot of things, he did not mention how to take care of re-strengthening the cut floor trusses. I will ask him what he recommends.

I’m going to try to attach his letter.

Last edited by bmcgin; 08-16-2009 at 04:28 AM. Reason: removed attachments....
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Old 08-14-2009, 09:22 AM   #6
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Floor Truss Shortening


Some floor trusses are available off-the-shelf with generically engineered webbing and I've been given the okay by engineers to alter them in much the same manner as you're referring to. That is to say, cut the truss and glue/nail plywood gussets to each side for 2' from the cut. The nails were to be in each member of the truss 3" spaced/staggered. At the end of the truss to be in the hanger, in my case, we were instructed to install a vertical member consisting of a doubled 2x block.
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Old 08-14-2009, 09:25 AM   #7
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Floor Truss Shortening


I like the caution at the end of the letter to temporarily support all loads. Yeah, that's definitely in order. I like to build temporary walls under both sides of where the beam goes in, making sure I'll be able to get the beam in place given the obstructions.
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Old 08-14-2009, 09:35 AM   #8
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Floor Truss Shortening


The beams specified are not LVL's they are PSL's. He's not showing floor trusses in the drawings he is showing 2" x 12" 16 o.c. Why didn't he spec what kind of engineered floor joists for the added area or is he just leaving that up to you and the supplier/manufacture? Looks pretty sloppy to me. He needs to be much more specific than that. Anybody can specify heavy duty Simpson joist hangers that doesn't really tell anybody anything. He needs to specify the type or model number also, then you can follow the installation instructions on the hanger for the fasteners. He also needs to show that there are trusses and specify the material to put them back together (i.e. mending plate, wood gusset, metal gusset, note these are examples only). I don't know how strict the building department is where you are but those would not fly at all where I'm at.
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Old 08-14-2009, 09:39 AM   #9
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Floor Truss Shortening


I've been on the engineering side of this fence many times, and on the contractors side of this fence many times. As a contractor, if I received these plans I would know what to do. As an engineer, I would have produced the same documentation, although we include the actual calcs and CAD drawings of the final connection details. I don't include assembly instructions unless I was asked for producing that and I'm being paid for it, but it's not normal that the property owner would ask me for that. We call these assembly instructions "means and methods." A contractor's means and methods are a closely guarded body of knowledge and experience, and the owner's engineer isn't normally called upon to come up with the contractor's means and methods of installation. In my opinion as a contractor and an engineer, it's the contractor's responsibility for building and maintaining his company's means and methods, and if it requires outside help to acquire that, then so be it.

But there is a process that goes on for situations like this, and it's an interaction between the engineer, contractor, and truss manufacturer. The trick in all of this is finding a good contractor, because you have a licensed engineer, and the truss manufacturers are very helpful.

When wearing the contractor's hat, if I have to cut through trusses in the fashion described here, I contact the truss manufacturer for an official recommendation, and they usually produce that recommendation with the caveat that it has to be blessed by a local PE. Usually I do that part for free as part of getting the work.

But I can see a contractor without a good body of means and methods or a PE on staff in weird situation: client has drawings from a PE that don't include every last detail on how to actually do the installation (assembly instructions), and the client wants me to bid on this, but I've never done this before so I don't know what to do.

Your best bet is to contact some experienced contractors, and ask them to look at the plans. If they say "well, we've done this before, but we need more detail on cutting and supporting the trusses," that's not necessarily a red flag. If they say you need to get the engineer to produce details on how to install this, and you go ahead and do that, please understand that you're basically paying for the contractor to take a class in how to cut and support trusses, which in turn is building up his body of means and methods.

But getting back to it, if the contractor says he needs more detail, in my opinion it's perfectly acceptable for you to say "I will be hiring a contractor that knows what he's doing and has experience in making this kind of change to a structure, and he will be expected to work with my engineer and the truss manufacturer on the details, and produce a safe structure in a manner that does not damage any existing elements." And then let the engineer, truss manufacturer, and the contractor hash it out.

If you're going to DIY this, then I strongly recommend that you tell the engineer this, and tell him that you'll need additional help in figuring out how to do the work safely. You'll have to pay for more engineering work to produce those assembly details, but you'll be safer in the long run. Also, contact the truss manufacturer first and get their input, and then call the engineer.
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Old 08-14-2009, 09:50 AM   #10
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Floor Truss Shortening


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Originally Posted by NailedIt View Post
I like the caution at the end of the letter to temporarily support all loads. Yeah, that's definitely in order. I like to build temporary walls under both sides of where the beam goes in, making sure I'll be able to get the beam in place given the obstructions.
That is a funny comment about supporting floor system.

I am planning on renting a bunch of SurePosts from a scaffolding company in lieu of building temp walls. Each one costs about $10 / month, seems like it’s worth it.
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Old 08-14-2009, 10:10 AM   #11
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Floor Truss Shortening


Aggie67, I hear what you are saying. I do want to DIY this with a very good handyman who has done a lot of work in our neighborhood. Ive seen this guy build decks, stairs, repair flashing, stucco walls, drywall, trim worketc Hes been in the business for 25 years and is very good (and reasonably priced).

He has not cut and re-supported engineered floor trusses. This part of the plan was his only grey area. With good instructions, Im confident we can do it. So Ill call the truss company and reconnect with the engineer.

With the drywall and insulation removed, and the truss in clear view, it looks pretty straight forward. I gave the engineer letter to the local lumber company so they can order all the correct parts.

I got a few bids from contractors (before the letter) and they wanted $8k-15k to do this over a 10 day span. We should be able to do the same for less than $3k.


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Old 08-14-2009, 11:00 AM   #12
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Floor Truss Shortening


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Originally Posted by bmcgin View Post
That is a funny comment about supporting floor system.

I am planning on renting a bunch of SurePosts from a scaffolding company in lieu of building temp walls. Each one costs about $10 / month, seems like its worth it.
Just make sure your support array covers both the vertical and shear loads. Last thing you want to do is cut the trusses and have the structure shift on you.
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Old 08-14-2009, 11:35 AM   #13
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Floor Truss Shortening


I'm not an engineer per education and certification, but wood-butchering framing expert I may purport to be, indeed. If I'm not mistaken, the sheer load ought to be sufficiently covered by the floor deck, which given that floor trusses are used I would expect to be glued and screwed plywood or OSB. Of course I would verify that. I've never heard of renting temporary columns for such an undertaking, however a temporary wall is relatively inexpensive given you aren't going to finish it with drywall, etc... A temporary wall can be laterally braced for sheer very easily with a couple of diagonal braces. You can reuse the lumber anyway. So, uh... well, the manufacturer's literature (simpson, etc...) should provide sufficient information to select the appropriate connectors to comply with your engineering recommendation. I'm referring to the catalog which should be available at your supplier. Make sure you don't use regular old framing nails for your connectors. Fasteners will be specified by the manufacturer of the joist-hanger. You might contact some experienced custom framers/ remodelers in your area. I'm one, but your local guys are the hands-on pros whom deal directly with compliance. It seems like a pretty straight-forward project you have going on and your engineering is about what I'd expect for such a situation. It's a good idea if you're not completely sure to just select the hardware by product ID and draw up exactly how you intend to apply it, including fasteners, adhesives, etc... and run it by whomever will be doing your inspection. Good luck with it.
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Old 08-14-2009, 12:53 PM   #14
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Floor Truss Shortening


The engineering is wrong. As ARI001 stated, he doesn't have 2x12 p.t. joists. Even if the S.E. had a trainee draw the plans, he supposedly reviewed them, which I doubt. You cannot build to these plans, they don't pertain. All important and necessary information is missing. Take it back and get your money back or redraw it. In my 36 years of framing, I have never seen such a outright blunder. Be safe, G
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Old 08-14-2009, 01:06 PM   #15
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The engineering is wrong. As ARI001 stated, he doesn't have 2x12 p.t. joists. Even if the S.E. had a trainee draw the plans, he supposedly reviewed them, which I doubt. You cannot build to these plans, they don't pertain. All important and necessary information is missing. Take it back and get your money back or redraw it. In my 36 years of framing, I have never seen such a outright blunder. Be safe, G
I may not have provided enough details. I would have to upload the cad drawings for the house to provide the full picture.

The house sits on 6' pilings, on top of the pilings are 2x12 floor joist, then subfloor. Then in between the 1st and 2nd floor are the 20” floor trusses.

So for beam #1, the engineer is saying to support the beam at one end by making a column of 3 2x4s. Then go under the house and locate the point below the column and add 3 2x12s to make sure the column does not break through the floor.


Last edited by bmcgin; 08-14-2009 at 01:10 PM. Reason: edited for grammer...
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