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Old 02-06-2015, 06:52 AM   #1
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Building a Roof over deck


Hi Everyone,
First I've tried to get multiple quotes for this project, but have just had contractors say they're to busy. Since I finished my basement myself and I'm pretty good with construction/anything do it yourself I've decided I'm going to build a roof over my deck myself to save some money and cut down on the rejection lol. I will be getting permits for this, so here is my basic drawing. The deck is 16' wide by 12' deep. So the roof will have a 1' overhand on all sides. I'm getting the trusses already made at Carter Lumber. I just need to frame it, then install the trusses

A couple questions:
1. The beam will sit on top of the 8x8" posts at one end. But how do I attach the other end to the house? Do I use joist hangers and attach it to the band joist? Or do I sit the beam just below the band joist and build a beam inside the wall to support it like in the other picture I have posted below? I just don't know how much the joist hanger can support. I'm also going to nail the truss that's flush against the house to the wall

2. The beam I will be using a 2 x 12 x 12 (2 pieces on each side sandwiched together). Is this Okay or do I need to use something else?

Any help or suggestions to my drawings would be great! I hope to start building in the next few weeks. I would be extremely grateful for any help in making this project a success!
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Building a Roof over deck-1.jpg   Building a Roof over deck-2.jpg   Building a Roof over deck-4952514465_50ae9b0841_z.jpg  

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Old 02-06-2015, 07:50 AM   #2
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Building a Roof over deck


This is a relatively small footprint roof. In order to determine the size for the beam, you need to calculate the total load on the beam, which is essentially half the roof load (presumably there is another beam on the opposite side). Roof load is generally driven by snow loading if you are in snow country, else wind loading may control. Your building inspector will be happy to show you the loads in your area, they will be clearly listed in the building code, and since you said you were getting a permit, you should discuss all loads with your building inspector before designing the structure (dead load, live load, seismic, impact, whatever the code requires you to design for). Codes vary from one location to another, so only your building inspector is authoritative.

As for the trusses you are getting, the picture you drew showed stick built rafters with a ridge board. If you are using trusses, the design will be different. You need to discuss loads with your truss manufacturer, typically they are very aware of local code requirements, and will design your trusses to meet local codes, but they will normally give you specific details about how to attach the trusses to the walls (or beam in your case). There are likely to be specific pieces of hardware required, maybe hurricane clips, and the spacing of the trusses will be dictated by the truss manufacturer. When you pull your permit, you typically list the type of truss you are using. Your idea of nailing the truss to the wall may not be acceptable to the truss manufacturer, you need to discuss this with them. I have never seen it done, not saying it never happens.

You can attach the roof to the house using a ledger board, but this requires careful flashing of the ledger. Or you can install a couple of posts and not structurally attach the roof to the house, but then you will need diagonal bracing to stiffen the framing. Best to discuss with the building inspector, they will likely have some ideas on how to do it. As to the capacity of specific joist hangars, that will be listed in the catalog by the manufacturer. Once you have calculated the load on each hangar, you will be able to select the appropriate size.

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Old 02-06-2015, 11:36 AM   #3
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Building a Roof over deck


Thanks for the reply! I originally was going to build the trusses myself, but just decided this week to purchase them since it shouldn't add to much to the overall cost. Once concern I had was getting the pitch right on each truss... so figured it would be less complicated to purchase them already built.

What would be the benefit in using a ledger board over just nailing the joist hanger to the band joist? My original plan was to just attach the joist hanger to the band joist of the house. Then I saw that image I posted previously where they built that 2x4 beam inside the wall to support the load. It was the only picture I could find of a gable roof attached which was still in the framing process. It made me rethink my attachment method. I prefer not to build the beam inside the wall just because that's a lot more siding I have to take off then cutting the house open could be another challenge since I have known water lines and electric running through. But if the Simpson strong ties won't hold the load, it may be my only option. I definitely don't want to do a free standing roof mainly because I do have water lines and electric lines running along the back of my house. Plus I feel that it would be more secure attaching it to a structure.

I researched the Simpson Strong tie. It's a double strong tie to fit (2) 2x12's. The strongest tie they have say:

DF/SP allowable loads
uplift 4095lbs
Floor 9100lbs
Snow 9100lbs

If that's to strong of a tie, they have other much cheaper ones rated around 5000lbs. That's if I use the 2x12 beam... the inspector may only say a 2x10 beam.

I'll have 2 of those ties on each side connected to the house plus half the weight will be on the (2) 8x8x12's at the other end. So I assume you have to take the total weight of the roof, plus any snow load, then divide by 4 to get the weight per tie? I can't see that exceeding 9100LBS (if I'm reading that correctly). But it makes me wonder how those can hold that much weight.

Here's a picture of my house if it'll be any help... the band joist is located 2' above my sliding door/windows. I've also send an email to the zoning dept asking for information on loads, etc.
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