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Attaching portico to house question

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  • Attaching portico to house question

    I would like to install a small portico over an exterior door supported by a couple of corbels. The portico will not exceed 20 inches out from the wall. We normally don't have much of a snow load, but i feel that the portico should be able to hold up the weigh of a person standing on it. I have been concidering how to attach the corbel to the wall. In a perfect world I'd like a stud to be behind it but this might not be the case so i was looking at 1/4 inch molly bolts to attach to the sheeting. I'd rather not open up the drywall in the interior to put in some sort of backing plate. Has anyone got any suggestions or comments on the holding power of molly bolts into OSB sheeting. Thanks.
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  • #2

    Re: Attaching portico to house question

    By "Moly" or "Molly" (I always knew them as "moly") you are thinking of this ?

    https://www.tmhardware.com/Hager-265...Nut-8S-JN.html

    H-265_2_%28LR%29.jpg

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    • #3

      Re: Attaching portico to house question

      Yes those are molly bolts - very nice ones.

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      • #4

        Re: Attaching portico to house question

        Originally posted by Bradpb View Post
        I would like to install a small portico over an exterior door supported by a couple of corbels. The portico will not exceed 20 inches out from the wall. We normally don't have much of a snow load, but i feel that the portico should be able to hold up the weigh of a person standing on it. I have been concidering how to attach the corbel to the wall. In a perfect world I'd like a stud to be behind it but this might not be the case so i was looking at 1/4 inch molly bolts to attach to the sheeting. I'd rather not open up the drywall in the interior to put in some sort of backing plate. Has anyone got any suggestions or comments on the holding power of molly bolts into OSB sheeting. Thanks.
        You can absolutely not attached anything into osb with molly bolts.

        You are either opening up the drywall to add blocking or opening up the siding.

        You should be removing the siding to install the portico, how would you flash it otherwise??

        Nathan

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        • #5

          Re: Attaching portico to house question

          No Moly's for me. I'm sure they will hold but that isn't the issue for me. The issue is you are only fastened to the sheathing so I don't care how well the moly's hold the sheathing could fail. Assuming the house has exterior siding, once you cut the siding to the face of the sheathing in the shape of your roof you will find all kinds of structure including a header over the door and studs either side of the door etc. Barring exactly what you would like to find you really need to fasten the corbels to structure. If the siding is removable it's super easy to find or build structure as easy as putting blocking between two studs etc.
          "Do it Right!"

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          • #6

            Re: Attaching portico to house question

            Rusty is correct. and be sure to flash it correctly or water will get down the back and into the wall.

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            • #7

              Re: Attaching portico to house question

              Thanks rusty for your answer , i was just looking for a yay or nay on the load bearing capacity of moly bolts on sheeting - not sure where you're going with the sleepless nights thing - your world i guess

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              • #8

                Re: Attaching portico to house question

                You have to remove the siding any way, so why not open the wall right up & install proper blocking. Big molly bolts would be strong enough, but the sheathing would not. It might be OK at first, but year by year you'd watch the portico sag bit by bit until something really bad happened.

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                • #9

                  Re: Attaching portico to house question

                  Originally posted by Bradpb View Post
                  Thanks rusty for your answer , i was just looking for a yay or nay on the load bearing capacity of moly bolts on sheeting - not sure where you're going with the sleepless nights thing - your world i guess
                  Is your house vinyl siding? As you can see from the responses they are all pretty much the same. If I were you I would do a gable end front not the hip roof one in your pic. I like the fish scale shingle front. If you can sorta confirm the size I would make up a template with the triangle and two corbels on a piece of plywood to confirm the fit before you start cutting etc. Sometimes you can move the corbels in or out if it helps to locate good structure. Try to get it as wide and as high as you can go otherwise you will be banging your head on the corbels.
                  Last edited by John Bartley; 01-03-2019, 09:08 PM. Reason: fixed quote
                  "Do it Right!"

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                  • #10

                    Re: Attaching portico to house question


                    I kinda cheated with this one because I had access to the insides and just added support where needed. Held on with 12 GRK RSS screws, 10" long. I chose not to make three big holes in the water tight building envelope for the braces (corbels) which would necessitate flashing etc, and just screwed right through the siding into the supports I put in there. This was mostly cosmetic but does keep some sun and weather off the doors as a bonus. If water makes it past the gable overhang, then makes it all the way down the siding to the roof of the portico, makes it past that then down to the corbel and gets past the top of the corbel down to a screw hole (which is filled with a screw) and then makes it into the screw hole and then makes it into the wall cavity and then actually causes a problem that is in excess of any problem that will occur when some little section of flashing fails over the next 30 years or so long before anyone notices and fixes it......I will be surprised.

                    20171127_113420.jpg
                    beachburl likes this.
                    Proud member of the Wadkin Blockhead Club.

                    http://www.youtube.com/c/DovetailTimberworks

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                    • #11

                      Re: Attaching portico to house question

                      Hey Brent you and I may be the only ones who would do that right through the siding. I have done many deck headers and gable extensions like that right thru the siding. I was always amazed at the negative comments I got from those who knew better, but my deck is done that way and never leaked a drop. 30 years and counting, but what do we know huh? By the way folks, drywall is super easy to fix but you would think you were asking someone to cut off a leg when you want to to put hole in the wall. LOL
                      timberframe likes this.
                      "Do it Right!"

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