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 Dornier 08-23-2013 08:07 PM

Deck beam help

1 Attachment(s)
I'm making a free standing, 10x12 to put an 8x8 little house on for the kids.

In the picture i have 2x10 running the short way.

Would 2 12-ft beams work running the long way? And where?

Attachment 75170

 liljohnny 08-23-2013 08:13 PM

It'll work if you use 6 piers/posts, you can't span the entire 12' with a 2ply 2X10 or even a 2X12. You might need a 3ply and even then I'm not sure....what you would get is excessive deflection/bounce imo.

 tony.g 08-24-2013 09:37 AM

As above, if the span is split, you would be OK with the two 12x2.
For the 10x2s spanning across at 18" c/s (or was it 16"?), you might get some bounce, depending on where you put the house. And there will also be kids jumping up and down. Perhaps space them a bit closer? (the beams, not the kids)

 Dornier 08-24-2013 10:29 AM

What do you mean if it is split with two 2x12? Wouldn't a 2x12 mean its going the entire way?

The house is going at one end, leaving a small "open deck" at the other end--with a rail of course.

I was thinking 2x10 @ 16" OC originally.

Would there be that much bounce doing 2 beams of 12 ft? Three beams?

How do you split beams?

And, would 6x6 be needed over 4x4?

Thanks!

 tony.g 08-24-2013 10:48 AM

I presume lilj. meant that you couldn't run the whole 12ft length with one 2x12 without it flexing too much. If you split the span by adding a post in the middle of each long side, that would mean you would be supporting each 2x12 at mid-span, meaning they were only spanning 6ft (hence he referred to 6 posts).
6x6 posts would be better, and easier to fix your beams to.

 joecaption 08-24-2013 11:01 AM

Use 6 X 6"s not 4 X 4's.
Not suppose to just nail the rim joist to the outsides of the post.
You need to notch the 6 X 6's so the rim joist are sitting on the beam not just on the sides.
Since you plan on building a building on top of this I'd ether build the building the same width as the deck or make the deck smaller.
If not waters going to get in under the walls and rot out the sheathing.
I'd also use two rim joist not one.
Make sure to use joist hangers.

 Dornier 08-24-2013 11:07 AM

Thanks. Good points on width.

 Dornier 08-24-2013 05:13 PM

1 Attachment(s)
UPDATE:

Attachment 75186

Everyone has given good guidance which made me rethink a few things, so bear with me.

I like the idea of 6x6 posts, and I hadn't planned on notching--just using metal mounts to put the beams square on top.

I don't have frost issue in Houston. When I was thinking 4x4 the plan was sunken pre-cast piers, back filled with gravel for drainage.

I'm not sure how to handle the knee braces for cross support for 6x6.

The deck boards would look nicer running the short way--which imitates running along the wall of a real house (since it'll have a house too). So:

That would mean my joists now run the long way (12ft) and my beams the short way (10 ft).

That makes me think (3) beams--made of two 2x10x10--would work.
This too would have 6 posts

From what I've been reading the joist lengths and beam spans are only a issue when "under-posted".

As for making the house wider, I had planning on running a bead along the base of the bottom plate on the walls' framing to help with moisture.

I'll stick an image in to explain what my brain thinks.

I shaded the "deck area", as well as the "house area".

The deck boards aren't to scale but you get the idea of their orientation, and they cover the entire area (10x12).

The joists are 16" OC.

The reddish bars are the beams--doubled up 2x10x10's.

As always, the help is appreciated.

 Ralph Coolong 08-27-2013 05:49 AM

Quote:
 Originally Posted by Dornier (Post 1233324) I'm making a free standing, 10x12 to put an 8x8 little house on for the kids. In the picture i have 2x10 running the short way. Would 2 12-ft beams work running the long way? And where? Just a little help please. Attachment 75170
Why don't you run a 6x6 pt beam right up the middle . On cement piers ?
Most builders build in the traditional manner of 2ply or 3 ply boards nailed together. Wen you nail two boards together water will rot them out in time. I built my deck 20 years ago using a beam to hold the deck joist up and have had no problem.

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