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  • Size of angle bar for roof trusses

    I am planning a project to install a roof DIY in a small area in my mother's house.
    The area is quite small (around 15'x15') and serves as a garage/driveway.

    A mono truss is the best and the simplest IMO. The truss would be installed along a wall on one end and supported by two existing concrete columns (part of the gate and fence structure).

    From a safety point of view, what size of angle bars should I use?

  • #2
    Re: Size of angle bar for roof trusses

    HI fourtheboys96,

    Is this related to the other thread that you were asking regarding the concrete slabs, just curious here. Anyway 15' is quite long for an angle bar to be used as your roofing trusses, probably a 3" X 3" X 1/4 inch thick, but hope you attach or weld some support to each other so that it will not sag. Another option for your trusses will be the use of 2" X 4" tubular with 1.5mm thickness, for sure this till be more sturdy provided they are all secured on both ends then use 2" X 2" X 1/4 inch thick as your purlins across to receive the galvanized roofing. Then you can secure your galvanized roof with Hex screws to the angle bars.




    HOPE this HELPS !!!
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    • #3
      Re: Size of angle bar for roof trusses

      Originally posted by rosy View Post
      HI fourtheboys96,

      Is this related to the other thread that you were asking regarding the concrete slabs, just curious here. Anyway 15' is quite long for an angle bar to be used as your roofing trusses, probably a 3" X 3" X 1/4 inch thick, but hope you attach or weld some support to each other so that it will not sag. Another option for your trusses will be the use of 2" X 4" tubular with 1.5mm thickness, for sure this till be more sturdy provided they are all secured on both ends then use 2" X 2" X 1/4 inch thick as your purlins across to receive the galvanized roofing. Then you can secure your galvanized roof with Hex screws to the angle bars.


      HOPE this HELPS !!!
      hahaha. It is indirectly related. The concrete slabs will be installed near the apartment where my wife and I live.
      This roof project is for my mother's (our ancestral) house. But both projects were as a result of an additional vehicle from my side. I will be lending our old car to my mother and I said it should have at least a roof.

      Maybe an angle bar is not sufficient to support the load.
      What do you call the steel bar that looks like two angle bars welded together (shaped like a T)?
      Maybe I can use this instead of a tubular steel.
      Anyway the truss will not support a load except for the weight of a few GI roof and the material itself.

      Comment


      • #4
        Re: Size of angle bar for roof trusses

        Hey bro fourtheboys96,

        That bar you are asking about is called a T-bar and usually used for the fabrication of steel casement windows. May I suggest that you don't use that for your trusses, not strong or sturdy enough, lulundo rin yan. It seems for your plan you are trying to minimize expenses as much as possible in materials.

        I will not stop you from doing so, that's your project but bear in mind I am giving you already proper tips on material to use. If you do not like using the rectangular tubings, there is another option to that, you can buy several pieces of GI pipes, 1/2" X 20' and fabricate your own trusses, it will be more fun too. Just cut pieces of pipes of about 6" or 8" in length then weld them to two parallel GI pipes in a diagonal positions. I guess this will be strong enough to carry the total weight of the angle bar purlins and the corrugated galvanized roofing.

        -----------------------------------------------------

        ANOTHER OPTION HERE:
        Bili ka na lang ng 2 piraso ng kawayan, then cut it to your required length size for your trusses, napaka mura lang ng kawayan, Php140 to Php180 per whole piece.
        Last edited by rosy; 11-13-2012, 12:13 PM.
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        -----------------------------------------------
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        Comment


        • #5
          Re: Size of angle bar for roof trusses

          Yeah I'm trying to minimize cost but my main priority is safety of the structure without overdoing it.
          I'm not doubting your suggestion. It's just that a lot of metal trusses I've seen including the one in our current parking area didn't use tubular steel, only T-bar or angle bars.

          Anyway, maybe we have a bit of misunderstanding.
          I plan to make a mono truss which has a bottom chord and top chord (looks like a right triangle) and a webbing in the middle. So the its design itself makes it sturdy.

          Maybe if I'm just going to hang the long metal materials as is, then I'll go for the tubular type material.

          Comment


          • #6
            Re: Size of angle bar for roof trusses

            hehehe, some misundestanding ?, may be yes, may be no, I don not know! but for sure I do understand you in trying as much as possible to minimize unwanted expenses on the future plan/project. Siguro bro di lang tayo nag kakasalubong ng iniisip na plano ng magiging construction. If you have seen in other private parking spaces using angle bars as its trusses on its roofing and you find it sturdy enough, then just go ahead with your plan, follow that, at least may pattern ka na na masusundan.
            HITRONIC 300 Amp DC Inverter IGBT Welder
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            Assorted Angle Grinders, Clamps and Vises


            -----------------------------------------------
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            • #7
              Re: Size of angle bar for roof trusses

              15' x 15' is not 'quite small', in that it implicates a considerable 4.6m span.
              You furthermore seem to be talking about just a single truss to support the
              roof purlins @ midspan, the purlin-ends supported by CHB wall, and it's not
              clear to me that your preexisting concrete columns are strong enough to
              support your truss.

              Anyway the truss will not support a load except for the weight of a few GI roof and the material itself.
              It will also support the additional dead load of purlins, plus occasional live loads
              (someone has to go up and install/paint/repair the roof, lol), and wind loads...
              and if you start hanging crap from it, like a ceiling and its joists, electricals and
              (God forbid) a chain hoist ... it starts to add up substantially.

              Anyway: assuming a typical pitch of 25-ish degrees, you might get away with
              50x50x6mm MS for your chords. 75x75x6mm might be a better choice, and
              any more might cross the line into overdesign-heaviness. Webbing section size
              will depend on what web configuration you choose. So will sizing your gusset
              plates: the fewer the webs, the lighter the truss, but the more-critical your
              weld connections. The broader your gussets, the longer the welds and the
              stronger your truss connections will be. Weld-quality is pretty important.

              What is also often overlooked is how critical your bearing points will be.
              Again, assuming your collumns are fit to support the truss, the best case is
              to use horizontally-oriented MS bearing plates, positioned flat on top of the
              aforementioned RC columns, and secured conventionally with rod or bolt
              anchors. Far less desirable is the use of steel dowels embedded along a
              vertical surface: those dowels will have to resist the shear load of the entire
              weight of the roof, purlins, truss, plus the aforementioned crap to be hung
              from it AND any wind loads.

              You may want to crossbrace the truss at midspan with 10mm threaded rod
              and turnbuckles, anchored to the walls on either side of the truss: I am just
              playing safe here, as I have zero idea what the wind/seismic conditions are
              where you're building this thing.

              tl;dr:

              Get a CE/SE graduate to design your truss for you.
              I know several licensed CE's (and one SE) who've given me more complex
              designs, for as little as a beer and a cheese sammich. Then again, they get
              a lot of paid work from me.
              Last edited by horge; 11-14-2012, 06:10 AM.

              Comment


              • #8
                Re: Size of angle bar for roof trusses

                @ fourtheboys96,

                hahaha, consider this advice from one of our reliable architects here in the forum !!!!!

                Thanks bro horge, very well explained.
                HITRONIC 300 Amp DC Inverter IGBT Welder
                YAMATO 300 Amp AC Stick Welder
                YAMATO 200Amp DC Inverter IGBT Welder
                DeWALT Chopsaw
                HOBART and ESAB Welding Helmets
                Assorted Angle Grinders, Clamps and Vises


                -----------------------------------------------
                Dreaming and wanting is good and healthy but working hard for it is better !

                Comment


                • #9
                  Re: Size of angle bar for roof trusses

                  Thanks a lot for your suggestion. although some of the terminologies not familiar to me, I can get a clearer picture now.

                  I'll try post some pics with actual measurements to get an accurate suggestion.

                  I'll see if I can ask some CE here in the university where I work.

                  Comment


                  • #10
                    Re: Size of angle bar for roof trusses

                    Hi! I did not have a chance to ask some engineers but I did have time to google.

                    But first, the exact dimension of the driveway I plan to have a roof is 4.10m x 3.20m (13.5'x10.5'). The span of the mono truss I am thinking of building is 4.10m.

                    This is the truss I am planning to make

                    http://www.nzdl.org/gsdlmod?e=d-0000...d3f516df.7.8.6

                    The shortest span of the truss in this book which uses angle bars is 6m which longer than what I am planning to make. Now I am a bit confident that angle bars can be used as a material for roof truss as long as there is enough webbing to support the compression and the tension load.

                    I am just figuring out the appropriate size of the angle bar.
                    I read in a blog of someone building a house somewhere in Panay (I know not the most scientifically source of info), angle bar of size 2"x2" 5mm thick was used for top and bottom chord and 2"x2" 3mm thick for webbing.
                    (He used a 2"x6" C purlins)

                    I assume I will use a smaller size angle bar than this.

                    I am considering only the dead load, wind load, and occasional rain.

                    Comment


                    • #11
                      Re: Size of angle bar for roof trusses

                      HI there again bro fourtheboys96,

                      See what I mean bro, when it comes to the design construction, hindi talaga tayo mag sasalubong kasi I have a different design in mind, so ang nangyayari hit and miss and mga replies. Its good you finally came up with an illustration of what you wanted. So you are thinking of uno aguas, I was thinking of that too, duon lang tayo nag salubong, hehehe

                      OK, YES angle bars will be enough for your trusses as long as there are enough webbing supports, plus maliit naman pala opening ng entrada ng garage, 3.20 m with a depth of 4.10 m. Anyway, how many are you planing to fabricate that mono trusses ?? Three units will do but four is better. May I suggest you use the 2" X 2"angle bars as your trusses and at the same time use it also as your purlins, pwede yan but do not skimp on the thickness kasi mabigat din ang galvanized roofing plus yung tao na sasampa at mag kakabit ng yero at mag di drill ng hex nuts.

                      Oh, I just remembered, what will support the middle truss/trusses, meron ba syang beam sa lower portion ng trusses connected sa two entrance posts?? just curious.

                      ------------------------------------------

                      I think for your roofing, you will be using 8 to 10 pcs of corrugated sheets of two varying lengths, isang de 10' at isang de 6'.
                      Last edited by rosy; 11-22-2012, 09:50 PM.
                      HITRONIC 300 Amp DC Inverter IGBT Welder
                      YAMATO 300 Amp AC Stick Welder
                      YAMATO 200Amp DC Inverter IGBT Welder
                      DeWALT Chopsaw
                      HOBART and ESAB Welding Helmets
                      Assorted Angle Grinders, Clamps and Vises


                      -----------------------------------------------
                      Dreaming and wanting is good and healthy but working hard for it is better !

                      Comment


                      • #12
                        Re: Size of angle bar for roof trusses

                        Don't worry Rosy. I already had a feeling we have two different designs in mind.
                        That is why I said in my previous post that maybe we just did not understand each other.

                        Comment


                        • #13
                          Re: Size of angle bar for roof trusses

                          Hi Bro fourtheboys96,

                          I suggest you use 1/4" x 2" x 2" Angle Bars for top and bottom chords and 3/16" x 1-1/2" x 1-1/2" for the web members. You can also use a smaller size of purlins, say 2" x 3" or 2" x 4" spaced at 0.70-0.80m on centers.

                          Fyi din lang, magaan lang ang G.I. roofing and purlins. Hindi ito critical sa dead load and liveloads. Mas critical ito sa windload. In fact, pagdating sa liveload, meron tayong tinatawag na liveload reduction sa code (this is due to the fact that the roofing is not loaded with liveload all the time, most likely, only during construction, so we can reduce the amount of live by a certain percentage).

                          Install also cross bracing at end spans for lateral support. A 10mm deformed or roundbar with turnbuckle will do.

                          You can use #12 x 35 steel tekscrew with hex. head and neoprene washer as fastener. Dont forget to include silicone sealant.

                          Regards,

                          Jay

                          Comment


                          • #14
                            Re: Size of angle bar for roof trusses

                            Originally posted by jayborre View Post
                            Hi Bro fourtheboys96,

                            I suggest you use 1/4" x 2" x 2" Angle Bars for top and bottom chords and 3/16" x 1-1/2" x 1-1/2" for the web members. You can also use a smaller size of purlins, say 2" x 3" or 2" x 4" spaced at 0.70-0.80m on centers.

                            Fyi din lang, magaan lang ang G.I. roofing and purlins. Hindi ito critical sa dead load and liveloads. Mas critical ito sa windload. In fact, pagdating sa liveload, meron tayong tinatawag na liveload reduction sa code (this is due to the fact that the roofing is not loaded with liveload all the time, most likely, only during construction, so we can reduce the amount of live by a certain percentage).

                            Install also cross bracing at end spans for lateral support. A 10mm deformed or roundbar with turnbuckle will do.

                            You can use #12 x 35 steel tekscrew with hex. head and neoprene washer as fastener. Dont forget to include silicone sealant.

                            Regards,

                            Jay
                            Thank you very much Sir Jayborre.

                            I plan to use angle bars instead of the usual C-purlins. Is this ok?

                            As for the cross bracing, should I attach it on the top chord or the bottom chord?

                            Comment


                            • #15
                              Re: Size of angle bar for roof trusses

                              I made a simple graphic design of what I am planning to do. I used Sketchup by Google.
                              The house itseld it not drawn to scale but the truss is. Any comments is welcome.



                              Sir Jayborre, is the 1/4" x 2" x 2" the minimum angle bar size for this project?

                              1/4" = 6mm?

                              I was reading this house construction blog (http://myphilippinelife.com/our-house-project-welding/ ) and their engineer specified the same size of bars.
                              Considering that they were making a much larger truss for a house, I was expecting a smaller angle bar for a 4m span truss of our garage.
                              Last edited by fourtheboys96; 11-29-2012, 02:59 PM.

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