Span of a 2x8 PT joist


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Old 04-04-05, 08:51 PM
Stephanie Brust
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Span of a 2x8 PT joist

I am building a front porch that is 36 feet in length and 8 ft wide. The foundation is continuos concrete block (3 courses) and I want to run the joist the 36 feet length in three sections of 12 feet each with 2 sets of double up beams to separate the sections. I am using 2x8 Pt for the joist. Do I need to put a pier underneath the 8 ft double beams or will they span the 8 feet ok and support the joists running side to side with joist hangers?
 
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Old 04-05-05, 03:18 AM
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edit- nm, thought you were talking about the roof vice the decking
 

Last edited by grover; 04-05-05 at 08:41 AM.
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Old 04-05-05, 05:16 AM
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Deck

2 x 8's will span 8' without a problem. Good Luck
 
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Old 04-05-05, 07:44 AM
J
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Run the joists the 8' direction at either 16" or 24" oc. depending on what you are using for decking. 12' is to long a span for 2x8's.

This way you won't need the double 2x8 beams and not nearly as many joist hangers.
 
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Old 04-06-05, 06:34 AM
Stephanie Brust
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If I run the joist 24 OC what do you recommend for the deck?
 
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Old 04-06-05, 06:52 AM
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Originally Posted by Stephanie Brust
I am building a front porch that is 36 feet in length and 8 ft wide. The foundation is continuos concrete block (3 courses) and I want to run the joist the 36 feet length in three sections of 12 feet each with 2 sets of double up beams to separate the sections. I am using 2x8 Pt for the joist. Do I need to put a pier underneath the 8 ft double beams or will they span the 8 feet ok and support the joists running side to side with joist hangers?
Which direction are you wanting to run the deck boards, the 8' direction or the 36' direction?

I'd go with running the joists the 8' length as well, but if that doesn't go with the way you want to run the deck boards you may need to run them the 36' direction anyway.

I'd go with 2x6 PT's for the deckboards, especially if you are 24 OC (which I wouldn't do, but that's preference). I've seen 1x6 at 16 OC, which I also wouldn't do. The difference between 16 and 24 for a 36' run is a whopping 9 boards. Boards and joists hangers add up to an additional $100, not a large amount for something you are to be walking on for a LONG time.
 
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Old 04-06-05, 07:26 AM
Stephanie Brust
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I want to run the deckboards the 8ft ( front to back). But I am concerned about the 36 ft length and how I should run the joist ( not so concerned with saving money on joist or hangers) Just like the way porches look running front to back rather than the length of a 36 ft front porch. What would you use if it were your house and how would you place the joist to ensure that that they don't sag. The length is 36 feet, the width is 8 ft, the foundation is 3 courses of concrete block continuous.

Thanks
 
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Old 04-06-05, 08:00 AM
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Sounds like you have a plan.

I think you will be ok on the 8' double beams, but I would support the 12' spans in the middle or they are going to bounce. Even a single post will do wonders.

*I* would run the deckboard parallel to the home, as that's my preference, and at 8', it's not enough to make a visual impact going perpendicular and would in fact, look rather odd *to me*. But it's not my deck, it's yours.
 
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Old 04-06-05, 08:20 AM
Stephanie Brust
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You know, I think you are right. I have gone back and forth on this one so many times but I think I will run the deck boards parallel and the joist the 8 ft width. ( as I do not like the sound of bounce if I run them 12). It's not enough difference to agonize over in the whole house bigger picture . Thanks so much!
 
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Old 04-06-05, 08:25 AM
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Hi Stephanie,

If you really want to run the deckboards perpendicular to the house then I would go with your original idea but reduce the distance between your beams to 8'. The 2x8 joists will span 8' without and problem and the dbl 2x8 beams will also work.

Personally, I would take a look at alternative decking materials ( composites ) because of the appearance and maintenance advantages. There are many options - most require 16" spacing of the joists, but there are some that will allow 24" spacing. You need to make this decision before framing so you provide the proper spacing.
 
  #11  
Old 04-06-05, 08:44 AM
Stephanie Brust
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Thanks Joe. We are going to space the joist 16 oc. We have looked at composites and they seem like a good idea. Thanks for your response.
 
 

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