Beam Supports For 8'x12' Deck With Roof - Building & Construction - DIY Chatroom Home Improvement Forum

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Old 05-06-2012, 07:44 PM   #1
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Beam supports for 8'x12' deck with roof

I am having a handyman add a deck to the front of my house to replace a crumbling concrete stoop. He will also be extending an existing roofline out to cover it. I did drawings and had them approved by the city and i am all set for permits. I hit a snag when i had the utility lines marked. The gas line falls directly in the center of the planned deck. I had planned for 3 support beams, but i am wondering if 2 would be sufficient for a 12' wide deck (joists would be 8' and supported by a ledger board on the house side), and if so, how should i space them?
Any advice would be appreciated!


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Old 05-06-2012, 08:09 PM   #2
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2 are fine just beef up the girder? Shouldn't the installer know this?


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Old 05-06-2012, 08:19 PM   #3
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I would use 2 X 10's for the rim joist and 2 X 8's for the floor joist 16" on center.
I also would avoid at all cost attaching a ledger to the side of the house and make the deck free standing if the ledger has to be attached in any way to the area where any siding is.
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Old 05-06-2012, 08:29 PM   #4
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There's a lot of fuzziness in your description. It sounds to me like you might be asking if a 2x8 joist spanning 12' would be a good idea. Even at 12"OC, it's either just within the acceptability range or outside it, depending on a number of factors. See

Personally, I would go with 2x10 joists.

Last edited by cortell; 05-06-2012 at 08:31 PM.
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Old 05-06-2012, 08:42 PM   #5
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Originally Posted by EmilyS View Post
I am having a handyman add a deck to the front of my house to replace a crumbling concrete stoop. !
Originally Posted by dvatt View Post
2 are fine just beef up the girder? Shouldn't the installer know this?
Put two and two together, she has a handyman doing it so probably not.
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Old 05-06-2012, 09:38 PM   #6
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My handyman may know the answer, but as the responsibility for making this to code is on me, I am trying to get as much info as possible. I am also tryin to determine where to dig the footers since my husband and I will be doing that part.
Unfortunately I can't afford to have a builder do the job. The quotes I got were significantly higher than what I will be paying my handyman.
Regarding the fuzziness of my question, I just re-read an realized I said 'beams' when really I meant posts. Big difference! Sorry about that! I do have to use a ledger board to attach it. The gas line runs perpendicular until about 6" from the house, then parallel and around the corner where it goes into my basement, so I am not able to dig close enough to the house for the footers to make it freestanding.
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Old 05-06-2012, 09:59 PM   #7
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You need to change the framing details of your plan (I think you know that though). Why not ask the guy that did your original plans to amend them to conform to the existing conditions?
I do this all the time for my clients that run into a situation like this. I have to charge extra of course but you can get the permit then and the handyman has a plan to go by.

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Old 05-06-2012, 10:11 PM   #8
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Possibly you located the gas line by calling Dig Safe, however in the event you have not done that, it is required, and a good idea besides, especially since you have a gas line out there. And as a word of caution, Dig Safe does not always locate lines on private property, and they don't always get the lines in the right place, this I can tell you from personal experience where we inadvertently dug up an unmarked gas line on a job that had been Dig Safed twice. Be very careful digging footers around a gas line, no need to blow yourself into the next county.

You should obtain a copy of the local deck code if you have not already, my town uses International Residential Code, no idea what yours uses, but the code will tell you the allowable span for a given joist size, and lots of other useful information.
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Old 05-07-2012, 08:04 AM   #9
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I would recommend a double 2x12 beam to span across the 12' from post to post, and for the post use 6x6 posts. for 8' joists that beam should work, do not go any smaller than a 2x12 for the beam. at the house do not use any bolts smaller than 5/8" diameter to attach ledger to house, and they have to be through bolt connections that connect to the band system of the house , no lag bolts. figure one bolt per 16" or 20" of ledger so about 9 or 10 bolts total and these bolts must be installed with a stagger affect along the ledger staying in from the top and bottom edges of the ledger 2 or 2.5".

so to recap, 2x12 used as beam and ledger, 2x8 floor joists, 6x6 posts.

much info derived from....
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Old 05-07-2012, 09:15 AM   #10
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@Andy - Thanks, Andy. I actually did the plans myself. My degree is in Interior Design and I use cad all the time, but it's for furniture reconfigures. I'm just not very familiar with the structural side of the design. We have a general contractor in my office today that works with us all the time. I am going to talk to him, so I will feel a lot better knowing that I have had professional look at the plan.

@Daniel - Thanks. YIKES! That's really scary about the gas line. I am trying to dig as far away from the marked line as possible.

Thanks to everyone else for your advice as well!


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beams , deck supports

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